Acta Paediatrica. 2022;00:1–13.  | 1wileyonlinelibrary.com/journal/apa 1  |  INTRODUC TION Since the 1970s, the lengths of the hospital stay (LOSs) for new- borns and their mothers after uncomplicated vaginal deliveries have steadily shortened, especially in developed countries, for example, in the United States, Canada and Sweden.1– 3 Early discharge (ED) has several advantages, including reduced costs, reduced risk of iat- rogenic infection and the opportunity for the mother and infant to Received: 15 November 2021  | Revised: 1 February 2022  | Accepted: 11 February 2022 DOI: 10.1111/apa.16290 O R I G I N A L A R T I C L E Association of early discharge with increased likelihood of hospital readmission in first four weeks for vaginally delivered neonates Maria Pohjanpää1  | Riitta Ojala1,2 | Tiina Luukkaala3,4 | Mika Gissler5,6,7,8 | Outi Tammela1,2 © 2022 The Authors. Acta Paediatrica published by John Wiley & Sons Ltd on behalf of Foundation Acta Paediatrica. Abbreviations: AGA, appropriate for gestational age; CCHD, critical congenital heart defect; CI, confidence interval; CRHC, care register for health care; ED, early discharge; GA, gestational age; ICU, intensive care unit; IQR, interquartile range; LGA, large for gestational age; LOS, length of hospital stay; MBR, Medical Birth Register; Md, median; OR, odds ratios; SD, standard deviation; SF, Statistics Finland; SGA, small for gestational age; THL, Finnish institute for health and welfare. 1Department of Paediatrics, Tampere University Hospital, Tampere, Finland 2Tampere Centre for Child Health Research, Tampere University, Tampere, Finland 3Research, Innovation and Development Centre, Tampere University Hospital, Tampere, Finland 4Health Sciences, Faculty of Social Sciences, University of Tampere, Tampere, Finland 5Information Services Department, THL Finnish Institute for Health and Welfare, Helsinki, Finland 6Research Centre for Child Psychiatry, University of Turku, Turku, Finland 7Region Stockholm, Academic Primary Health Care Centre, Stockholm, Sweden 8Department of Molecular Medicine and Surgery, Karolinska Institute, Stockholm, Sweden Correspondence Maria Pohjanpää, Department of Paediatrics, Pirkanmaa Hospital District, Tampere University Hospital, Tampere, Finland. Email: maria.pohjanpaa@tuni.fi Funding information No external funding was received. Abstract Aim: The main aim was to determine whether hospital readmission rates by 28 days of age are elevated with early discharge (ED) in Finland. We sought to identify the causes and predictors of ED, readmission rates, admissions to the intensive care unit (ICU) and death. Methods: The data of 333,321 infants were retrieved from nationwide registers. Vaginally delivered single infants at gestational ages (GAs) of ≥37+0, born in 2008– 2015 and treated in any maternity ward in Finland, were included. ED was defined as discharge on the day of birth or after one night stay on the maternity ward. Results: During the study period, the ED and hospital readmission rates increased. Low- risk infants and those born in high population- density areas were more likely to be discharged early. ED predicted hospital readmission but not ICU admission or death. The most common reason for readmission was jaundice, followed by infection. ED seemed not to predict severe cardiologic problems. Rather than ED, being born at 38+0– 38+6 weeks’ GA significantly predicted ICU admission or death. Conclusion: Early discharge seems to be associated with increased hospital readmis- sion. Birth at 38+0– 38+6 weeks’ GA was a significant predictor of ICU admission or death, as opposed to early discharged infants. K E Y W O R D S early discharge, full- term, hospital readmission, newborn discharge timing This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes. 2  |    POHJANPÄÄ et Al. recover in a familiar, home environment.3,4 However, ED may hold potential risks. As an example, critical congenital heart defects (CCHDs), jaundice and gastrointestinal obstructions may not appear within one to two days after birth.5– 9 ED may also lead to fewer op- portunities for healthcare practitioners to guide breastfeeding and parenting.10 Reduced LOSs have been associated with increased readmis- sion rates, especially due to jaundice.10 According to a report from California (1992– 1995), discharging a neonate on the day of birth in- creased the risk of infant readmission.4 However, no significant risk was detected if the newborn was discharged one day after birth. In Finland, the average LOS for newborns decreased from 3.7 days in 2006 to 2.9 days in 2015.11,12 In total, 5.7% of neonates were dis- charged at 0– 1 days’ age and 27.4% at 2 days’ age in 2015.12 There are many recent studies concerning early postpartum discharge, but sparse information is available in the Nordic countries concern- ing the outcomes of healthy term neonates discharged early from delivery hospitals. Therefore, the aim of this study was to investi- gate whether ED after uncomplicated vaginal delivery is associated with increased hospital readmission rates by the time infants reach 28 days old. The authors also aimed to establish the causes and pre- dictors of ED, along with readmission rates, admissions to the inten- sive care unit (ICU) and death. 2  |  PATIENTS AND METHODS 2.1  |  Selection of the study population The number of live births in Finland from 2008 to 2015 was 471,232.13 A national register study included 333,321 vagi- nally delivered, liveborn single babies at gestational ages (GAs) of ≥37+0 weeks treated on a maternity ward. Infants born via caesarean section were excluded since they usually stay in the hospital longer given their mothers’ indications. Also, infants born out of the hospi- tal, admitted after birth to the neonatal ICU, or admitted after birth to another paediatric ward at the same or another hospital, were excluded. Infants with chromosomal anomalies were included only if those anomalies were detected after the perinatal period. Finally, 412 infants and mothers with missing information on the date of discharge, or who were discharged when the infant's age was more than 28 days, and 13,230 newborns with discrepant data across the registers, were excluded. In Finland, paediatricians examine all newborns before discharge. If the check- up occurs when the infant is <24 h old, newborns are in- vited to a prescheduled re- examination by the paediatrician, usually at three to five days of age. Infants discharged at the age of <48 h and infants with risk factors will be referred to check- up to outpa- tient clinic run by a midwife at the hospital. In the remaining cases, a public healthcare nurse checks the newborn at 3– 7 days of age. Data on infants and mothers were collected from the Medical Birth Register (MBR), run by the Finnish Institute for Health and Welfare (THL). This register includes data on livebirths and stillbirths at birthweights of at least 500 g or GAs of at least 22+0 weeks. The MBR’s data sources are maternity hospitals and the Population Information System headed by the Digital and Population Data Services Agency and Cause- of- Death Register, Statistics Finland (SF). The validity of the MBR has been proven reliable.14,15 Data on readmissions and hospital stays were collected from the Care Register for Health Care (CRHC), also maintained by the THL. The CRHC contains information on admissions, discharges, diagno- ses, procedures and interventions. The dates and causes of death were obtained from SF. The information from the MBR, CRHC and SF was linked individually via each infant's anonymised personal identity code made by recordkeeping authorities. 2.2  |  Exposure Neonates were analysed in three groups according to their discharge days: (1) discharged on the day of birth (1st day), (2) discharged one day after birth (2nd day) and (3) discharged beyond day after birth (after 2nd day). Infants discharged on the 1st or 2nd day were de- fined as discharged early. The covariates included can be seen in Tables 1 and 2. Regions were divided according to five university hospital areas: southern (population density ~87/km2), eastern (~13/km2), northern (~5/km2), western (~27/km2) and southwestern (~34/km2). GAs were catego- rised as 37+0– 38+6 (early term), 39+0– 40+6, 41+0– 41+6 and ≥42+0 (post- term). Small for gestational age (SGA) and large for gestational age (LGA) were defined as a birthweight of ≤−2 or ≥+2 standard de- viations (SDs), respectively, according to the national sex- specific standard.16 Causes of readmission were categorised into 11 groups according to the International Statistical Classification of Diseases and Related Health Problems, Tenth Revision (ICD- 10), as follows: lower respira- tory infectious diseases (J09– J18, J20– J22 and A37); other infectious diseases (A02.1, A40, A41, P36, A04.3, A39, A85, A87 and B00) in- cluding inflammatory diseases of the central nervous system (G00– G09), soft tissue infections (A46, H00.03, L03, H05.0 and P38), bone and joint infections (M00, M86) and urinary tract infections (N10, N12, N39.0 and P39.3); and gastrointestinal problems including congeni- tal lactase deficiency (E73.0), gastrointestinal obstruction and acute Key Notes • The early discharge (less than two nights’ stay) and hos- pital readmission rates increased among low- risk new- borns born in Finland. • Infants discharged early had an increased risk of read- mission to hospital but not of admission to the intensive care unit (ICU) or death, by 28 days’ age. • Being born at 38+0– 38+6 weeks’ gestational age pre- dicted admission to the ICU or death by 28 days’ age.     |  3POHJANPÄÄ et Al. TA B L E 1  Characteristics of infants and their mothers Day of discharge 1st day 2nd day After 2nd day p- Value* (n = 2,089; 0.6%) (n = 24,296; 7.3%) (n=306,936; 92.1%) 1st day vs. after 2nd day 2nd day vs. after 2nd day Mother Age (years), n (%) <0.001 <0.001 <20 11 (0.5) 120 (0.5) 7,056 (2.3) 20– 24 238 (11.4) 2,904 (12.0) 48,680 (15.9) 25– 29 665 (31.8) 7,626 (31.4) 98,087 (32.0) 30– 34 723 (34.6) 8,973 (36.9) 99,394 (32.4) 35– 39 379 (18.1) 3,969 (16.3) 44,095 (14.4) ≥40 73 (3.5) 704 (2.9) 9,624 (3.1) Marital status, n (%) Married 1,305 (62.5) 15,089 (62.1) 17,7209 (57.7) <0.001 <0.001 Cohabiting 1,905 (91.4) 22,560 (92.9) 278,246 (90.8) 0.601 <0.001 Socioeconomic group, n (%) <0.001 <0.001 Upper- level employees 727 (34.8) 9,514 (39.2) 135,694 (44.2) Lower- level employees 3 (0.1) 50 (0.2) 1,071 (0.3) Entrepreneurs 59 (2.8) 626 (2.6) 7,031 (2.3) Manual workers 230 (11.0) 2,377 (9.8) 34,446 (11.2) Students 149 (7.1) 1,915 (7.9) 28,800 (9.4) Pensioners 0 (0.0) 2 (0.0) 91 (0.0) Others1 107 (5.1) 975 (4.0) 11,160 (3.6) BMI, n (%) <0.001 <0.001 <18.5 84 (4.0) 915 (3.8) 11,411 (3.7) 18.5– 24.9 1,326 (63.6) 15,644 (64.5) 192,102 (62.8) 25– 29.9 395 (18.9) 4,770 (19.7) 63,680 (20.8) ≥30 184 (8.8) 2,280 (9.4) 33,058 (10.8) Pregnancy Primipara, n (%) 37 (1.8) 580 (2.4) 97,739 (31.8) <0.001 <0.001 Previous miscarriages, n (%) 521 (24.9) 5,887 (24.2) 64,780 (21.1) <0.001 <0.001 Smoking, n (%) <0.001 <0.001 Stopped smoking during 1st trimester 90 (4.3) 1,214 (5.0) 18,119 (5.9) Smoked after 1st trimester 298 (14.3.) 2,626 (10.8) 26,385 (8.6) Prenatal visits Median (IQR) 13 (11– 16) 14 (12– 16) 15 (13– 18) <0.001 <0.001 At the hospital clinic, median (IQR) 2 (1– 3) 2 (1– 3) 3 (1– 4) <0.001 <0.001 Insulin treatment started during pregnancy, n (%) 10 (0.5) 212 (0.9) 4,530 (1.5) <0.001 <0.001 Gestational diabetes2, n (%) 18 (0.9) 921 (3.8) 29,862 (9.7) <0.001 <0.001 Delivery Birth hospital level, n (%) <0.001 <0.001 University 566 (27.1) 8,625 (35.5) 102,229 (33.3) (Continues) 4  |    POHJANPÄÄ et Al. abdomen (K31.1, Q40.0, K40.3, K56, P76, Q41, Q42, Q43.1, R10.0, K63.1 and K65), hepatic failure (K72), gastrointestinal haemorrhage (K92, P54.0 and P54.1) and biliary atresia (Q44.29). Diagnoses P57– P59 and R17 were categorized as jaundice. Haematologic problems included haemolytic anaemia (D59), coagulation disorder (D65, D66) and haemolytic disease of the foetus and newborn (P55 and P56). Hypoglycaemia and inadequate nutrition included hypoglycaemia (P70.4), dehydration (P74.1 and E86), insufficient feeding (P92.3, P98.2 and E40– E46) and abnormal weight loss (R63.4). Cardiologic problems included hypertension (I15), endocarditis and myocarditis (I38 and I51.4), cardiac arrest (I46), paroxysmal tachycardia (I47), heart failure (I50), persistent foetal circulation (P29.31) and cardiac defects (Q20, Q21.30, Q25.1, Q25.21, Q25.6, I35.0 and I37.0). Neurologic problems included convulsions (G40, G41, P90 and G47.3), intracranial Day of discharge 1st day 2nd day After 2nd day p- Value* (n = 2,089; 0.6%) (n = 24,296; 7.3%) (n=306,936; 92.1%) 1st day vs. after 2nd day 2nd day vs. after 2nd day Central 1,030 (49.3) 10,500 (43.2) 149,333 (48.7) Other3 493 (23.6) 5,171 (21.3) 55,374 (18.0) Gestational age, n (%) <0.001 <0.001 37+0– 37+6 31 (1.5) 341 (1.4) 12,265 (4.0) 38+0– 38+6 159 (7.6) 2389 (9.8) 37,759 (12.3) 39+0– 40+6 1,371 (65.6) 15,242 (62.7) 178,741 (58.2) 41+0– 41+6 452 (21.6) 5,427 (22.3) 64,645 (21.1) ≥42+0 76 (3.6) 897 (3.7) 13,525 (4.4) Mode of vaginal delivery, n (%) <0.001 <0.001 Normal vaginal 2,062 (98.7) 23,644 (97.3) 273,409 (89.1) Breech delivery 9 (0.4) 117 (0.5) 1,983 (0.6) Instrumental delivery4 18 (0.9) 535 (2.2) 31,544 (10.3) Time of birth, n (%) <0.001 <0.001 Morning (8:00 AM– 3:00 PM) 474 (22.7) 6,211 (25.6) 85,293 (27.8) Evening (3:00 PM– 10:00 PM) 55 (2.6) 3,470 (14.3) 99,241 (32.3) Night (10:00 PM– 8:00 AM) 1,559 (74.6) 14,612 (60.1) 122,195 (39.8) Day of birth, n (%) 0.752 0.924 Weekday 1,544 (73.9) 17,890 (73.6) 225,922 (73.6) Weekend 545 (26.1) 6,406 (26.4) 81,014 (26.4) Newborn Sex, male, n (%) 1,045 (50.0) 11,965 (49.2) 153,822 (50.1) 0.934 0.009 Birthweight, mean (IQR)5 3,612 (3,350– 3,865) 3,626 (3,350– 3,880) 3,566 (3,260– 3,860) <0.001 <0.001 SGA 2 (0.1) 34 (0.1) 3,889 (1.3) AGA 2,079 (99.5) 24,067 (99.1) 297,598 (97.0) LGA 8 (0.4) 195 (0.8) 5,431 (1.8) Resuscitation, n (%) 1 (0.0) 22 (0.1) 424 (0.1) 0.267 0.052 One- min Apgar 0– 6, n (%) 13 (0.6) 267 (1.1) 9,708 (3.2) <0.001 <0.001 Phototherapy, n (%) 19 (0.9) 246 (1.0) 12,836 (4.2) <0.001 <0.001 Note: *p- values were tested via Pearson's chi- squared test or Kruskal– Wallis test. IQR= interquartile range. 1Others include, for example, unemployed and full- time mothers. 2Mothers’ diabetes: gestational diabetes= O24; DM1= E10; DM2= E11. 3Other include regional hospitals and healthcare centres. 4Instrumental delivery includes, for example, forceps and vacuum extraction. 5Birthweight. Abbreviations: AGA, appropriate for gestational age; LGA, large for gestational age; SGA, small for gestational age. TA B L E 1  (Continued)     |  5POHJANPÄÄ et Al. TA B L E 2  Predictors of early discharge after birth Early discharge (ED) (N = 26,385) All (N = 333,321) ED (n = 26,385) Multivariable adjusted for ED* n (%) p OR (95% CI) Mother Primipara No 234,965 25,768 (11.0) 1 Yes 98,356 617 (0.6) <0.001 0.05 (0.04, 0.05) BMI 18.5– 30 278,593 22,184 (8.0) <0.001 1 <18.5 12,410 999 (8.0) 0.007 1.10 (1.02, 1.18) ≥30 35,732 2,477 (6.9) <0.001 0.82 (0.78, 0.86) Age 25– 29 years 106,378 8,291 (7.8) <0.001 1 <25 years 59,009 3,272 (5.5) <0.001 0.91 (0.87, 0.95) 30– 34 years 123,684 11,084 (9.0) <0.001 0.91 (0.88, 0.93) ≥35 years 44,250 3,737 (8.4) <0.001 0.75 (0.72, 0.78) Smoking No 277,189 21,469 (7.7) <0.001 1 Yes 48,732 4,228 (8.7) <0.001 1.27 (1.23, 1.32) Gestational age 39+0– 40+6 195,354 16,613 (8.5) <0.001 1 37+0– 37+6 12,637 372 (2.9) <0.001 0.36 (0.33, 0.41) 38+0– 38+6 40,307 2,548 (6.3) <0.001 0.77 (0.74, 0.81) 41+0– 41+6 70,524 5,879 (8.3) 0.10 1.02 (1.00, 1.06) ≥42+0 14,498 973 (6.7) 0.007 0.91 (0.85, 0.97) Mode of vaginal delivery Normal vaginal 29,915 25,706 (8.6) <0.001 1 Breech delivery 2,109 126 (6.0) 0.09 0.84 (0.70, 1.03) Instrumental delivery1 32,097 553 (1.7) <0.001 0.30 (0.27, 0.33) Time of birth Morning (8:00 AM– 3:00 PM) 91,978 6,685 (7.3) <0.001 1 Evening (3:00 PM– 10:00 PM) 102,766 3,525 (3.4) <0.001 0.46 (0.44, 0.48) Night (10:00 PM– 8:00 AM) 138,366 16,171 (11.7) <0.001 1.76 (1.70, 1.81) Place of birth University hospital 111,420 9,191 (8.2) <0.001 1 Central hospital 160,863 11,53 (7.2) <0.001 0.65 (0.63, 0.68) Other2 61,038 5,664 (9.3) <0.001 0.68 (0.64, 0.70) University hospital's catchment area Southern 131,202 14,260 (10.9) <0.001 1 Eastern 45,158 2,301 (5.1) <0.001 0.35 (0.34, 0.37) Northern 53,673 1,029 (1.9) <0.001 0.12 (0.11, 0.13) Western 54,030 5,154 (9.5) <0.001 0.69 (0.66, 0.71) Southwestern 48,634 3,580 (7.4) <0.001 0.53 (0.51– 0.56) (Continues) 6  |    POHJANPÄÄ et Al. haemorrhages (P52.0 and I60– 169) and malformations of the central nervous system (Q00– Q07). Injuries were categorised as S00– T74. The category of other included social problems (Z59, Z63, Z75 and Z81) and neonatal withdrawal symptoms (P96.1 and P04). Mild con- ditions, which could not be included in any category, were defined as ‘miscellaneous, minor causes’— for example, medical observations and suspicions of diseases or conditions. 2.3  |  Outcomes The main endpoint was infant readmission to any hospital ward after discharge by the age of 28 days. The secondary measures were the causes and predictors of ED, ICU admissions or death by the time infants were 28 days old. The causes of ICU admissions and detailed factors of deaths were clarified. 2.4  |  Statistical analyses Either Pearson's chi- squared test, the Kruskal– Wallis test or Cochran– Armitage trend test was used in group comparisons, as appropriate. Potential predictors of ED, readmission, ICU admis- sion and/or death were analysed via multivariable logistic regres- sion analysis. The covariates used can be seen in Table 3. Risk factors of readmission were analysed by dividing the groups into three categories (1st, 2nd and after 2nd day discharge) and into two categories (ED and discharge after the 2nd day). The results were presented as odds ratios (ORs) and 95% confidence intervals (CIs). Statistical analyses were performed with IBM SPSS Statistics for Windows, versions 24 and 25 (IBM Corp., released 2013). A p- value of < 0.05 was considered statistically significant. 2.5  |  Missing data The date of hospital discharge was missing for 1.4% of the new- borns. In case of a missing date, the mother's date of hospital dis- charge was used in healthy newborns. The missing data for other variables were as follows: cohabitation (4.4%), socioeconomic group (29.5%), smoking (2.2%), prenatal visits (2.1%) and prenatal visits at the hospital clinic (4.2%). The proportions of all other variables were less than 1%. Early discharge (ED) (N = 26,385) All (N = 333,321) ED (n = 26,385) Multivariable adjusted for ED* n (%) p OR (95% CI) Newborn Sex Female 166,489 13,375 (8.0) 1 Male 166,832 13,010 (7.8) 0.15 0.98 (0.96, 1.01) One- min Apgar 7– 10 323,121 26,093 (8.1) 1 0– 6 9,988 280 (2.8) <0.001 0.51 (0.45, 0.58) Birthweight3 AGA 323,744 26,146 (8.1) <0.001 1 SGA 3,925 36 (0.9) <0.001 0.13 (0.09, 0.18) LGA 5,634 203 (3.6) <0.001 0.38 (0.33, 0.44) Phototherapy No 320,220 26,120 (8.2) 1 Yes 13,101 265 (2.0) <0.001 0.39 (0.34, 0.43) Year of birth 2008– 2009 85,714 4,986 (5.8) <0.001 1 2010– 2012 127,082 9,935 (7.8) <0.001 1.40 (1.35, 1.46) 2013– 2015 120,525 11,464 (9.5) <0.001 1.87 (1.81, 1.94) Note: *Multivariable- adjusted logistic regressions were used, and results are shown by odds ratios (ORs) with 95% confidence intervals (CIs). 1: Instrumental delivery including, for example, forceps and vacuum extraction. 2: Other includes regional hospitals and healthcare centres. 3: Birthweight. Abbreviations: AGA, appropriate for gestational age; LGA, large for gestational age; SGA, small for gestational age. TA B L E 2  (Continued)     |  7POHJANPÄÄ et Al. T A B L E 3   P re di ct or s of r ea dm is si on , a dm is si on t o IC U o r de at h (a ge ≤ 28 d ay s) R ea dm is si on (N = 1 0, 4 43 ) IC U o r D ie d (N = 8 7) N Ye s M ul ti va ri ab le * Ye s M ul ti va ri ab le * (3 33 ,3 21 ) n (% ) p O R (9 5% C I) n (% ) p O R (9 5% C I) M ot he r P ri m ip ar a N o 23 4, 96 5 7, 74 9 (3 .3 ) 1 63 (< 0. 1) 1 Ye s 98 ,3 56 2, 69 4 (2 .7 ) <0 .0 01 0. 77 (0 .7 3, 0 .8 0) 24 (< 0. 1) 0. 63 0. 88 (0 .5 3, 1 .4 7) B M I (< 0. 1) 18 .5 – 2 9. 9 27 8, 59 3 8, 50 4 (3 .1 ) 0. 02 1 70 (< 0. 1) 0. 89 1 <1 8. 5 12 ,4 10 40 6 (3 .3 ) 0. 29 1. 06 (0 .9 5, 1 .1 7) 3 (< 0. 1) 0. 91 0. 93 (0 .2 9, 2 .9 8) ≥3 0 35 ,7 32 1, 32 7 (3 .7 ) 0. 0 02 1. 10 (1 .0 3, 1 .1 7) 14 (< 0. 1) 0. 44 1. 26 (0 .7 0, 2 .2 4) A ge 2 5– 29 y ea rs 10 6, 37 8 3, 18 8 (3 .0 ) <0 .0 01 1 27 (< 0. 1) 0. 16 1 <2 5 ye ar s 59 ,0 09 1, 90 5 (3 .2 ) <0 .0 01 1. 15 (1 .0 8, 1 .2 2) 23 (< 0. 1) 0. 12 1. 58 (0 .8 9, 2 .7 9) 30 – 3 4 ye ar s 12 3, 68 4 3, 91 8 (3 .2 ) 0. 68 1. 01 (0 .9 6, 1 .0 6) 25 (< 0. 1) 0. 41 0. 80 (0 .4 6, 1 .3 8) ≥3 5 ye ar s 44 ,2 50 1, 43 2 (3 .2 ) 0. 44 0. 98 (0 .9 1, 1 .0 4) 12 (< 0. 1) 0. 82 1. 08 (0 .5 4, 2 .1 7) Sm ok in g N o 27 7, 18 9 8, 69 0 (3 .1 ) 0. 88 1 67 (< 0. 1) 0. 65 1 Ye s 48 ,7 32 1, 52 1 (3 .1 ) 0. 68 0. 99 (0 .9 3, 1 .0 5) 18 (< 0. 1) 0. 36 1. 29 (0 .7 5, 2 .2 1) G es ta ti on al a ge 39 +0 – 4 0+ 6 19 5, 35 4 5, 52 5 (2 .8 ) <0 .0 01 1 47 (< 0. 1) 0. 01 1 37 +0 – 3 7+ 6 12 ,6 37 93 9 (7 .4 ) <0 .0 01 1. 97 (1 .8 3, 2 .1 2) 6 (< 0. 1) 0. 33 1. 54 (0 .6 4, 3 .6 8) 38 +0 – 3 8+ 6 40 ,3 07 2, 11 9 (5 .3 ) <0 .0 01 1. 67 (1 .5 8, 1 .7 6) 21 (< 0. 1) 0. 02 1. 89 (1 .1 2 , 3 .1 8) 41 +0 – 4 1+ 6 70 ,5 24 1, 54 9 (2 .2 ) <0 .0 01 0. 80 (0 .7 6, 0 .8 5) 8 (< 0. 1) 0. 08 0. 51 (0 .2 4, 1 .0 7) ≥4 2+ 0 14 ,4 98 31 1 (2 .1 ) <0 .0 01 0. 79 (0 .7 1, 0 .8 9) 5 (< 0. 1) 0. 20 1. 82 (0 .7 2, 4 .6 2) M od e of v ag in al d el iv er y N or m al v ag in al 29 ,9 15 9, 31 8 (3 .1 ) 0. 25 1 82 (< 0. 1) 0. 07 1 B re ec h de liv er y 2, 10 9 71 (3 .4 ) 0. 59 0. 94 (0 .7 3, 1 .1 9) 2 (< 0. 1) 0. 22 2. 44 (0 .5 8, 1 0. 20 ) In st ru m en ta l de liv er y1 32 ,0 97 1, 05 4 (3 .3 ) 0. 12 1. 06 (0 .9 9, 1 .1 3) 3 (< 0. 1) 0. 06 0. 32 (0 .1 0, 1 .0 3) Ti m e of b irt h M or ni ng (8 :0 0 A M – 3 :0 0 PM ) 91 ,9 78 2, 85 1 (3 .1 ) 0. 04 1 24 (< 0. 1) 0. 93 1 (C on tin ue s) 8  |    POHJANPÄÄ et Al. R ea dm is si on (N = 1 0, 4 43 ) IC U o r D ie d (N = 8 7) N Ye s M ul ti va ri ab le * Ye s M ul ti va ri ab le * (3 33 ,3 21 ) n (% ) p O R (9 5% C I) n (% ) p O R (9 5% C I) Ev en in g (3 :0 0 PM – 10 :0 0 PM ) 10 2, 76 6 3, 34 8 (3 .3 ) 0. 17 1. 04 (0 .9 9, 1 .0 9) 30 (< 0. 1) 0. 71 1. 11 (0 .6 5, 1 .9 0) N ig ht (1 0: 0 0 PM – 8: 0 0 A M ) 13 8, 36 6 4, 23 3 (3 .1 ) 0. 50 0. 98 (0 .9 4, 1 .0 3) 33 (< 0. 1) 0. 80 0. 93 (0 .5 5, 1 .5 8) P la ce o f b ir th U ni ve rs ity ho sp ita l 11 1, 42 0 3, 42 1 (3 .1 ) <0 .0 01 1 42 (< 0. 1) 0. 49 1 C en tr al h os pi ta l 16 0, 86 3 4, 92 0 (3 .1 ) <0 .0 01 1. 10 (1 .0 5, 1 .1 5) 41 (< 0. 1) 0. 73 1. 09 (0 .6 9, 1 .7 1) O th er 2 61 ,0 38 2, 10 2 (3 .4 ) <0 .0 01 1. 23 (1 .1 6, 1 .3 1) 4 (< 0. 1) 0. 30 7 0. 57 (0 .1 9, 1 .6 8) U ni ve rs ity h os pi ta l's c at ch m en t a re a So ut he rn 13 1, 20 2 4, 10 2 (3 .1 ) <0 .0 01 1 7 (< 0. 1) <0 .0 01 1 Ea st er n 45 ,1 58 1, 38 3 (3 .1 ) 0. 23 1. 04 (0 .9 8, 1 .1 1) 11 (0 .1 ) 0. 0 09 3. 74 (1 .4 0, 1 0. 01 ) N or th er n 53 ,6 73 1, 64 9 (3 .3 ) <0 .0 01 0. 80 (0 .7 6, 0 .8 6) 5 (< 0. 1) 0. 65 1. 31 (0 .4 0, 4 .2 7) W es te rn 54 ,0 30 1, 68 0 (3 .1 ) 0. 28 0. 97 (0 .9 1, 1 .0 3) 41 (< 0. 1) <0 .0 01 11 .5 8 (4 .9 2 , 2 7. 30 ) So ut hw es te rn 48 ,6 34 1, 61 4 (3 .1 ) 0. 21 1. 04 (0 .9 8, 1 .1 1) 23 (< 0. 1) <0 .0 01 7. 61 (3 .1 5, 1 8. 34 ) N ew bo rn Se x Fe m al e 16 6, 48 9 4, 79 5 (2 .9 ) 1 43 (< 0. 1) 1 M al e 16 6, 83 2 5, 64 8 (3 .4 ) <0 .0 01 1. 12 (1 .0 8, 1 .1 7) 44 (< 0. 1) 0. 89 0. 97 (0 .6 4, 1 .4 8) O ne - m in A pg ar 7– 10 32 3, 12 1 10 ,1 37 (3 .1 ) 1 82 (< 0. 1) 1 0– 6 9, 98 8 30 2 (3 .0 ) 0. 10 0. 90 (0 .8 0, 1 .0 2) 5 (0 .1 ) 0. 09 2. 26 (0 .8 9, 5 .7 2) B ir th w ei gh t3 A G A 32 3, 74 4 10 ,0 43 (3 .1 ) 0. 00 1 1 86 (< 0. 1) 1. 00 1 SG A 3, 92 5 12 2 (3 .1 ) 0. 33 0. 91 (0 .7 6, 1 .1 0) 1 (< 0. 1) 1. 00 0. 96 (0 .1 3, 6 .9 6) LG A 5, 63 4 27 6 (4 .9 ) <0 .0 01 1. 27 (1 .1 2 , 1 .4 4) 0 (< 0. 1) 0. 98 - - P ho to th er ap y N o 32 0, 22 0 8, 60 2 (2 .7 ) 1 76 (< 0. 1) 1 Ye s 13 ,1 01 1, 84 1 (1 4. 1) <0 .0 01 5. 33 (5 .0 2 , 5 .6 4) 11 (0 .1 ) 0. 0 02 2 .9 2 (1 .4 9, 5 .7 2) Ye ar o f b irt h T A B L E 3   (C on ti nu ed )     |  9POHJANPÄÄ et Al. 2.6  |  Ethics approval This study was approved by the Ethics Committee of the Pirkanmaa Hospital District, THL and SF. 3  |  RESULTS 3.1  |  Timing and predictors of early discharge In total, 7.9% (n = 26,385) of newborns were discharged early, that is, on the 1st or 2nd day, and this percentage increased over time (Figure 1). According to Cochran– Armitage trend test, the yearly change was statistically significant between 1st or 2nd and after 2nd day (<0.0001) but not between 1st and 2nd day (p = 0.107). In this ED group, most of the mothers were ≥30 years old or upper- level employees, and most of the newborns were born at the central hospital (Table 1). The predictors of ED are presented in Table 2. 3.2  |  Readmission Of all neonates, 3.1% (n = 10,443) were readmitted to the hospi- tal by the time they reached 28 days of age. The infants discharged after the 2nd day were readmitted less often than those discharged earlier (Table 3). Readmission rates increased over time, especially among infants discharged early (Figure 2). According to Cochrane– Armitage trend test, the proportion of early discharged increased during time period from 2008 to 2015 (p = 0.0005). In all university hospital areas, the readmission rates were simi- lar: 3.1%– 3.3%. The time between hospital discharge and readmis- sion was the shortest among infants discharged on the 1st day (1st day median (Md): 5.0, interquartile range (IQR): 2.0– 13.5; 2nd day Md: 7.0, IQR 3.0– 16.0; after 2nd day Md: 7.0, IQR: 2.0– 15.0). The overall difference between groups was p = 0.039, and the pairwise comparisons were as follows: 1st versus 2nd day: p = 0.049; 2nd veresus after 2nd day: p = 0.034; 1st versus after 2nd day: p = 0.174. Of the infants readmitted, most initial readmissions occurred at the age of <7 days (32.5%, n = 3,398). Following this, 29.7% (n = 3,097) were initially readmitted at 7– 13 days old, 19.2% (n = 2,008) at 14– 20 days old and 18.6% (n = 1,940) at 21– 27 days old (p < 0.001). The number of readmissions ranged from one to five, but 94.0% (n = 9,817) were readmitted only once. 3.3  |  Causes of readmission The most common reasons for readmission were ‘miscellaneous, minor causes’, especially among infants discharged on the 1st day. The most common single cause for readmission was jaundice (30.9%), followed by infection (20.6%). Readmission because of hy- poglycaemia and inadequate nutrition affected 0.3% of newborns R ea dm is si on (N = 1 0, 4 43 ) IC U o r D ie d (N = 8 7) N Ye s M ul ti va ri ab le * Ye s M ul ti va ri ab le * (3 33 ,3 21 ) n (% ) p O R (9 5% C I) n (% ) p O R (9 5% C I) 20 08 – 2 00 9 85 ,7 14 2, 20 6 (2 .6 ) <0 .0 01 1 5 (< 0. 1) <0 .0 01 1 20 10 – 2 01 2 12 7, 08 2 4, 10 0 (3 .2 ) <0 .0 01 1. 28 (1 .2 2 , 1 .3 5) 12 (< 0. 1) 0. 37 1. 62 (0 .5 7, 4 .6 0) 20 13 – 2 01 5 12 0, 52 5 4, 13 7 (3 .4 ) <0 .0 01 1. 30 (1 .2 3, 1 .3 7) 70 (< 0. 1) <0 .0 01 10 .1 0 (4 .0 7, 2 5. 06 ) D is ch ar gi ng g ro up D is ch ar ge a ft er 2n d da y 30 6, 93 6 9, 56 3 (3 .1 ) 1 78 (< 0. 1) 1 Ea rly d is ch ar ge 26 ,3 85 88 0 (3 .3 ) <0 .0 01 1. 15 (1 .0 7, 1 .2 4) 9 (< 0. 1) 0. 54 1. 25 (0 .6 1, 2 .5 8) N ot e: *M ul ti va ri ab le - a dj us te d lo gi st ic r eg re ss io ns w er e us ed , a nd r es ul ts a re s ho w n by o dd s ra ti os (O R s) w it h 95 % c on fi de nc e in te rv al s (C Is ). 1 I ns tr um en ta l d el iv er y in cl ud es , f or e xa m pl e, fo rc ep s an d va cu um e xt ra ct io n. 2 O th er in cl ud e re gi on al h os pi ta ls a nd h ea lth ca re c en tr es . 3 B ir th w ei gh t. A bb re vi at io ns : A G A , a pp ro pr ia te f or g es ta ti on al a ge ; L G A , l ar ge f or g es ta ti on al a ge ; S G A , s m al l f or g es ta ti on al a ge . T he B ol d va lu es a re s ta ti st ic al ly s ig ni fi ca nt . T A B L E 3   (C on ti nu ed ) 10  |    POHJANPÄÄ et Al. discharged on the 1st day, and 0.1% of newborns discharged on the 2nd day and after the 2nd day (p = 0.003) (Table S1). Other categories contained no statistical differences between neonates discharged on the 1st or 2nd day or after the 2nd day. Some in- fants had more than one diagnosis code registered as the reason for readmission. 3.4  |  Risk factors for readmission The risk factors of readmission were analysed in two different ways, by dividing the groups into two (ED and discharge after the 2nd day) or three (1st, 2nd and after 2nd day discharge) catego- ries. ED was a significant risk factor for readmission in the analysis divided into two discharge groups (Table 3). Additionally, infants of mothers with BMIs ≥30 or aged <25 years, as well as infants born at 38+0– 38+6 weeks’ GA, in central or other hospitals, who were male, were LGA, with a history of phototherapy or born after the year 2009, were statistically significantly more likely to be readmitted. Infants of primiparae, with GAs of ≥41+0 weeks, or born in the northern university hospital area had a decreased risk of readmission (Table 3). The multivariable analysis in which three discharge groups were included detected the same significant risk factors as the first anal- ysis with minor, insignificant differences in p- values, ORs and CIs. An ‘after 2nd day’ discharge was associated with decreased risk of readmission (OR 0.88 (95% CI 0.82, 0.95) p < 0.001), while 1st day discharge was not a statistically significant risk factor for readmis- sion (OR 1.21 (95% CI 0.96, 1.53) p = 0.114). 3.5  |  Admission to ICU and mortality Table 3 presents risk factors for ICU admission or death; early dis- charge was not a significant predictor of either. In total, 75 newborns were admitted to the ICU. Nine (12.0%) of these infants were discharged on the 2nd day and 66 (88.0%) after the 2nd day; none were discharged on the 1st day. Of the infants F I G U R E 1  Mean length of stay at the hospital and percentages of neonates discharged on the 1st day, 2nd day and after 2nd day post- birth F I G U R E 2  Percentages of neonates readmitted to the hospital by the age of 28 days     |  11POHJANPÄÄ et Al. admitted to the ICU, 24 (32.0%) were born at 37– 38+6 and 20 (27.0%) at 38+0– 38+6 weeks’ GA. Considering their ages, 34 (45.3%) neonates were admitted to the ICU at <7 days old. The proportions of infants admitted to the ICU increased over time. In 2008, 2/100,000 neonates were admitted to the ICU; in 2011, 7/100,000; in 2012, 12/100,000; in 2013, 54/100,000; in 2014, 47/100,000; and in 2015, 64/100,000 (p < 0.001). No ne- onates were admitted to the ICU in 2009 or 2010. ICU admission rates differed notably among the university hospital areas. In the southern area, 2/100,000 neonates were admitted to the ICU; in the eastern area, 18/100,000; in the northern area, 7/100,000; in the western area, 74/100,000; and in the southwestern area, 43/100,000 (p < 0.001). The causes of ICU admission included infections (n = 25), gastro- intestinal problems (n = 25), neurologic problems (n = 9), respiratory problems (n = 6) and cardiologic problems (n = 2), and a further eight infants were admitted for observation. Jaundice was the most com- mon single cause, followed by respiratory tract infections. In nine of the latter cases, respiratory syncytial virus was diagnosed. Nine other neonates were readmitted because of sepsis— two early onset and the remaining late onset. In the early- onset cases, no specific or- ganisms were detected. Among the late onset cases, one was caused by streptococci, one by staphylococci and one by a gram- negative organism. All 12 newborns who died had been discharged at ≥2 days old. The causes of death were sudden infant death syndrome in five, car- diologic problems in four (including oneCCHD, hypoplastic left heart syndrome) and infections in two cases. 4  |  DISCUSSION 4.1  |  Principal findings Post- birth LOS for healthy, vaginally delivered single babies was shortened, and hospital readmission rates increased over time. Neonates discharged early were more likely to be low- risk infants born in areas with high population densities. History of photother- apy before discharge was the most common risk factor, and jaun- dice was the most common single cause of hospital readmission. ED, including infants discharged on the 1st or 2nd day, predicted readmission. Nevertheless, the 1st day discharge did not seem to be a significant, independent risk factor for readmission. The rates of ICU admission and mortality were extremely low, and ED seemed not to be associated with these outcomes. However, birth at 38 weeks’ GA was a significant predictor of ICU admission or death. 4.2  |  Strengths of the study A strength of this study was that it involved a population- based, com- plete, national cohort with a large number of cases. Using linked data from several national health registers served as a valid method.17 It was possible to obtain information about diagnoses, complications and causes of death from the registers— providing comprehensive, reliable data. 4.3  |  Limitations of the data The MBR and hospital record data do not contain time labels, and thus, the authors were unable to analyse exactly how many hours old the newborns were when examined by the paediatrician and when discharged. Information on breastfeeding would also have been helpful for establishing factors behind jaundice, hypoglycaemia and inadequate nutrition. 4.4  |  Interpretation The increasing global trend of ED was seen in this population. The mean LOS has, in many countries, become much shorter than that in Finland. In California4 12%— and in England,18 up to 90%— of new- borns are discharged within 2 days of vaginal birth. ED is a concept that has no standardised definition, and it varies markedly between different countries and hospitals, as well as between publications (Table 4). The discharge time is associated with parity of birth, infant and psychosocial factors.1,2,19 As predictive, factors necessitating longer Publication Year of publication Country Definition of early discharge Danielsen, et al.4 2000 United States ≤48 h (very early ≤24 h) Zimmerman, et al.6 2003 Israel ≤24 h or less Isayama, et al.9 2020 Canada <48 h Farhat, et al.10 2011 Lebanon ≤48 h Nilsson, et al.19 2017 Denmark 13– 50 h (very early ≤12 h) Meara, et al.29 2004 Unites States Within 1 day Our definition Finland ≤2nd day TA B L E 4  Definitions of early discharge of neonates according to earlier publications 12  |    POHJANPÄÄ et Al. follow- up periods for either the mother or the neonate, for example, primiparous or older mothers and early or post- term infant or in- fants required phototherapy were less likely to be discharged early. As found in previous research,19 mothers’ smoking was associated with ED. It is possible, that the smokers do not feel comfortable in the hospitals, where smoking is prohibited and are therefore eager to get discharged as soon as possible. The readmission rate and significant predictors (ED and male sex) of readmission, coincided with earlier research (e.g., readmission rate 25– 30/1,000 in California and 32/1,000 in Canada).3,4,10 However, in our study, the difference in readmission was slight between ED newborns and those who were not dis- charged early. Jaundice was the most common single cause of readmission and ICU admission, but no kernicterus cases were found. In our study, infants born at 38+0– 38+6 weeks’ GA were at an increased risk of readmission, in contrast to infants born at 37+0– 37+6 weeks’ GA. The healthcare professionals tend probably to be more cautious with the infants born at <38 weeks GA, and thus, smaller proportions of these less mature infants are discharged early. Infants of primiparous mothers have, in earlier research, been found to be at an increased risk of readmission.4 The present find- ings, in contrast, might be explained by the fact that infants of prim- iparous mothers were less likely to be discharged early. The incidence of early- onset sepsis was also low as since 2013, in Finland, the THL has recommended routine antenatal screening for vaginal carriage of group B streptococcus and antepartum antibiotic prophylaxis.20 Newborns with increased risk of neonatal sepsis are monitored more closely than they were before, and they now have a longer LOS.21 Births in lower than tertiary- level hospitals were associated with increased risk of readmission, but births in northern Finland were associated with decreased risk of readmission. Inside Finland, there were also significant geographical differences concerning ICU ad- mission. These findings could be explained, at least partly, by differ- ences between travelling distances from the hospital to home in the north and south, discharge practices and registration procedures in hospitals. Sudden infant death syndrome, as well as cardiologic and circu- latory issues, including one CCHD, were the most common causes of death in the present sample. CCHDs have occurred in 19.1/10,000 births across 12 countries and approximately 8.85 million births.22 On average, the prenatal detection rate has been 50%, ranging be- tween 13% and 87% among centres.22 After 2006, pulse oximetry screens were distributed to most delivery hospitals in Finland.23,24 Both high- quality prenatal diagnostics and nationwide neonatal pulse oximetry screening may explain the low rate of adverse events related to CCHDs in the sample. Birth at 38 weeks seemed associated with increased risk of readmission to the ICU or death. A previous Finnish register study25 also reported that being born early term was associated with low Apgar scores, perinatal mortality and adverse neurologic outcomes. A correlation between ED and mortality has been previously established in a few single- unit studies. Yet, among 7,009 infants in one study, there were no deaths in the ED group by the time the infants were 30 days old.26 Furthermore, no correlation be- tween a shorter LOS and death by the age of 14 days was found among 920,554 neonates in another.27 Accordingly, none of the twelve newborns who died in the present study population were discharged early. Many studies indicate that ED is safe for neonates if certain cri- teria are followed and if early follow- up visits are arranged.28,29 This, combined with appropriate prenatal and early postnatal diagnostics and screening systems in Finland, has created a structure in which well- selected neonates can be discharged early after birth without increased risk of adverse events. 5  |  CONCLUSION The ED and hospital readmission rates among low- risk newborns increased over the study period. This study shows that ED is margin- ally associated with the risk of readmission to the hospital. Yet, ED did not seem to predict ICU admission or death. Instead, infants born at 38+0– 38+6 weeks’ GA had an increased risk of admission to the ICU or death within four weeks after birth. CONFLIC T OF INTERE S T The authors have no conflicts of interest to declare. ORCID Maria Pohjanpää https://orcid.org/0000-0001-6818-9434 R E FE R E N C E S 1. Vanpee M, Rylander E, Bergius H, Marchini G. Sortie pré- coce de maternité des nouveau- nés bien portants: expérience Scandinave. Arch Pediatr. 2009;16(6):709- 710. doi:10.1016/S0929 - 693X(09)74121 - 1 2. Centers for Disease Control and Prevention, (CDC). Trends in length of stay for hospital deliveries — United States, 1970– 1992. MMWR Morb Mortal Wkly Rep. 1995;44(17):335- 337. https://www.jstor. org/stabl e/23305730 3. Liu S, Wen SW, McMillan D, Trouton K, Fowler D, McCourt C. Increased neonatal readmission rate associated with decreased length of hospital stay at birth in canada. Can J Public Health. 2000;91(1):46- 50. 4. Danielsen B, Castles AG, Damberg CL, Gould JB. Newborn dis- charge timing and readmissions: California, 1992- 1995. Pediatrics. 2000;106(1):31- 39. http://pedia trics.aappu blica tions.org/cgi/conte nt/abstr act/106/1/31 doi:10.1542/peds.106.1.31 5. Brousseau T, Sharieff GQ. Newborn emergencies: the first 30 days of life. Pediatr Clin North Am. 2006;53(1):69- 84. doi:10.1016/j. pcl.2005.09.011 6. Zimmerman DR, Klinger G, Merlob P. Early discharge after de- livery. A study of safety and risk factors. ScientificWorldJournal. 2003;3:1363- 1369. doi:10.1100/tsw.2003.108 7. Ewer AK. Review of pulse oximetry screening for critical con- genital heart defects in newborn infants. Curr Opin Cardiol. 2013;28(2):92- 96. https://journ als.lww.com/co- cardi ology/ Abstr     |  13POHJANPÄÄ et Al. act/2013/03000/ Review_of_pulse_oxime try_scree ning_for_criti cal.3.aspx Accessed Oct 15, 2021 doi:10.1097/HCO.0b013 e3283 5d7e42 8. Juang D, Snyder CL. Neonatal bowel obstruction. Surg Clin North Am. 2012;92(3):685- 711. https://www.clini calkey.es/playc onten t/1- s2.0- S0039 61091 2000588 doi:10.1016/j.suc.2012.03.008 9. Isayama T, O'Reilly D, Beyene J, Shah P, Lee S, McDonald S. Hospital care cost and resource use of early discharge of healthy late preterm and term singletons: a population- based cohort study and cost analysis. J Pediatr. 2020;226:96- 105.e7. https://www- scien cedir ect- com.libpr oxy.tuni.fi/scien ce/artic le/pii/S0022 34762 0307630 Accessed Oct 28, 2021 10. Farhat R, Rajab M. Length of postnatal hospital stay in healthy new- borns and re- hospitalization following early discharge. N Am J Med Sci. 2011;3(3):146- 151. doi:10.4297/najms.2011.3146 11. Vuori E, Gissler M. Vastasyntyneet 2006. 2008. http://urn.fi/ URN:NBN:fi- fe201 20419 4285 12. Gissler M. Personal communication. 2021. 13. Finland, Statistics. Official Statistics of Finland (OSF). Births (e- publication). Web site. https://pxnet2.stat.fi/PXWeb/ pxweb/ fi/ StatF in/StatF in__vrm__synt/statf in_synt_pxt_12dj.px/table/ table ViewL ayout 1/https://pxnet2.stat.fi:443/PXWeb/ api/v1/fi/StatF in/vrm/synt/statf in_synt_pxt_12dj.px 14. Gissler M, Teperi J, Hemminki E, Merilainen J. Data quality after restructuring a national medical registry. Scand J Soc Med. 1995;23(1):75- 80. doi:10.1177/14034 94895 02300113 15. Gissler M, Shelley J. 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Pediatrics. 2004;113(6):1619- 1627. doi:10.1542/peds.113.6.1619 SUPPORTING INFORMATION Additional supporting information may be found in the online version of the article at the publisher’s website. How to cite this article: Pohjanpää M, Ojala R, Luukkaala T, Gissler M, Tammela O. Association of early discharge with increased likelihood of hospital readmission in first four weeks for vaginally delivered neonates. Acta Paediatr. 2022;00:1– 13. doi:10.1111/apa.16290