Prematurity, smallness-for-gestational age and later hospital admissions: A nation-wide registry study

doi:10.1016/j.earlhumdev.2015.02.010

Early Human Development

Volume 91, Issue 5, May 2015, Pages 299-306

https://doi.org/10.1016/j.earlhumdev.2015.02.010 Get rights and content

Highlights

•
Pre- and perinatal conditions affect disease later in life.
•
Using nationwide registries we examined altered disease patterns.
•
Children born small/premature showed altered risk of disease.
•
These changes were seen throughout childhood and early adult life.
•
Disease patterns were altered in many organ systems.

Abstract

Introduction

Being born premature or small for gestational age (SGA) is known to be associated with diseases later in life, such as gestational diabetes, hypertension and pre-eclampsia. In this study we examined the association between being born premature or SGA and all diseases diagnosed during hospital admissions later in life.

Methods

Using Danish nation-wide registries we created a cohort of 1,348,106 persons born 1974–1996 and assessed all unique diagnoses registered in the Danish Patient Registry (DPR) for hospital admissions in the period 1994–2007 (n = 27,910,558). We determined the odds ratios for persons born premature or SGA using multivariate logistic regression.

Results

A total of 15,059 unique ICD‐10 diagnosis codes were represented in the period. Only diagnoses used at least 100 times were included in the analysis (n = 4175). Of these 838 showed an odds ratio that was statistically significantly different from unity for people born premature or SGA. After correcting for multiple testing, 250 remained significant. The diagnoses covered diseases in most organ systems, including cardiovascular, endocrinological, infectious, neurological/neurosurgical, obstetric, orthopedic, psychiatric, lung & urological diseases, and occurred throughout childhood and early adulthood. Novel findings included increased risks for delayed puberty, neurofibromatosis type 1 and ileus and decreased risks of mononucleosis, peritonsillar abscesses, chronic hypothyroidism and several types of fractures and contusions later in life.

Conclusion

Being born premature or SGA was associated with significantly altered risks of being admitted to a hospital with a wide range of diseases later in life, affecting almost all organ systems throughout childhood and early adulthood. Our findings may motivate testing in other cohorts and search for novel mechanisms of pathogenesis.

Introduction

Smallness for gestational age (SGA) and prematurity are known to be important risk factors for infant mortality and morbidity and development of disease in adult life [1]. The hypothesis of the developmental origins of adult disease, also known as the Barker hypothesis, states that intrauterine conditions affect the risk of disease later in life, especially cardiovascular disease [2], [3]. Many studies have confirmed this hypothesis, and SGA has been shown to be associated with development of gestational diabetes mellitus, pre-eclampsia as well as type 2 diabetes later in life [4], [5], [6], [7]. Preterm birth is also a risk factor for the same diseases, partly due to the high incidence of SGA in the preterm population, and possibly due to postnatal growth restriction [7].

SGA and preterm birth have also been shown to be associated with a wide range of complications related to perinatal pathology, among others retinopathy of prematurity, necrotizing enterocolitis and cerebral palsy [8], [9], [10], [11]. It has long been recognized that late effects may appear in the first years of life but recently evidence shows that the effects of SGA and prematurity may appear in early and late adulthood [12], [13], [14]. Data from the Dutch Famine Cohort shows that children exposed for intrauterine famine are at increased risk of not only cardiovascular disease, but also obesity, obstructive airway disease, stress sensitivity and breast cancer [15].

The Danish national health registries are considered of very high quality, and have registered data on all hospital admissions since 1977. With this study, we wanted to examine if persons born premature or SGA had an increased risk of being diagnosed with other diseases and conditions during hospital admission later in life, by examining all unique diagnoses in the Danish National Patient Registry.

Section snippets

Data

Data were extracted in December 2008 from the Danish Medical Birth Registry (MBR) and The National Patient Registry (NPR), both held by The National Board of Health in Denmark, and The Educational Registry held by Statistics Denmark. A data extraction done for a study on the risk of psychiatric disorders in children and young adults born preterm was used for the present analysis [16].

All persons born in or immigrated to Denmark are assigned a Central Personal Registry (CPR) number and data from

Ethics

The data collection for the study was approved by the Danish Data Protection Agency. The CPR numbers were encrypted and thus anonymized for the researchers. Under Danish legislation it is not necessary to apply for approval by The Danish National Committee on Biomedical Research Ethics for database studies, as long as the study is approved by the Danish Data Protection Agency. Nor is it necessary to get written consent from individuals for database studies.

Statistical analysis

The incidence of each of the 4915 diagnoses was calculated for all persons in the cohort. To distinguish the effects of SGA and prematurity, we created a multivariate logistic regression model, that included gestational age (completed days of gestation) as a continuous variable, being born SGA (defined as birthweight ≤ − 2 SD of expected, calculated from the normal fetal growth reference), as well as highest completed education (four categories as described in the above), sex, and year of birth

Results

Of the 4915 unique diagnoses 838 (17.0%) showed significantly increased or decreased risk for persons born SGA or premature, before correction for multiple testing. After the correction for multiple testing, 259 diagnoses remained significant (5.3%). Nine of these diagnosis codes concerning birthweight and gestational age were not included in the graphs and further calculations, due to their tautological nature (Table 1), leaving 250 significant associations. SGA was associated with increased

Discussion

We applied a theory-free ‘datamining’ method to a nation-wide dataset on hospital admissions combined with a conservative, adjusted step-down Bonferroni–Holm method to calculate p-values. We found associations between being born SGA or preterm and odds of hospital admissions for a wide range of diseases and conditions, from birth to adulthood. In a bird's eye view, rather than random statistical false positives, we think that it represents the complexity of early human development—not

Conflicts of interest

None declared

References (65)

D.J. Barker et al.
Weight in infancy and death from ischaemic heart disease
Lancet
(1989)
J. Dempsey
Weight at birth and subsequent risk of preeclampsia as an adult
Am J Obstet Gynecol
(2003)
L.A. Plante
Small size at birth and later diabetic pregnancy
Obstet Gynecol
(1998)
E. Blair et al.
Intrauterine growth and spastic cerebral palsy
Am J Obstet Gynecol
(1990)
T. Roseboom et al.
The Dutch famine and its long-term consequences for adult health
Early Hum Dev
(2006)
S. Jarvis et al.
Cerebral palsy and intrauterine growth in single births: European collaborative study
Lancet
(2003)
S.-L. Rudanko et al.
Visual impairment in children born prematurely from 1972 through 1989
Ophthalmology
(2003)
F. Delange et al.
Increased risk of primary hypothyroidism in preterm infants
J Pediatr
(1984)
J. Christensen et al.
Validation of epilepsy diagnoses in the Danish National Hospital Register
Epilepsy Res
(2007)
S.P. Johnsen et al.
Predictive value of stroke and transient ischemic attack discharge diagnoses in The Danish National Registry of Patients
J Clin Epidemiol
(2002)

T.B. Larsen et al.

A review of medical records and discharge summary data found moderate to high predictive values of discharge diagnoses of venous thromboembolism during pregnancy and postpartum

J Clin Epidemiol

(2005)

R.W. Thomsen et al.

Validity and underrecording of diagnosis of COPD in the Danish National Patient Registry

Respir Med

(2011)

D.D. McIntire et al.

Birth weight in relation to morbidity and mortality among newborn infants

N Engl J Med

(1999)

H. a De Boo et al.

The developmental origins of adult disease (Barker) hypothesis

Aust N Z J Obstet Gynaecol

(2006)

K.E. Innes et al.

A woman's own birth weight and gestational age predict her later risk of developing preeclampsia, a precursor of chronic disease

Epidemiology

(1999)

R. á Rogvi et al.

Women born preterm or with inappropriate weight for gestational age are at risk of subsequent gestational diabetes and pre-eclampsia

PLoS One

(2012)

D.J. Murphy et al.

Neonatal risk factors for cerebral palsy in very preterm babies: case–control study

BMJ

(1997)

J.C. Rivera et al.

Understanding retinopathy of prematurity: update on pathogenesis

Neonatology

(2011)

J.A. Morgan et al.

Pathogenesis and prevention of necrotizing enterocolitis

Curr Opin Infect Dis

(2011)

C. Levy-Marchal et al.

Long-term metabolic consequences of being born small for gestational age

Pediatr Diabetes

(2004)

E. Kajantie et al.

Size at birth as a predictor of mortality in adulthood: a follow-up of 350 000 person-years

Int J Epidemiol

(2005)

M. Hack et al.

Outcomes in young adulthood for very-low-birth-weight infants

N Engl J Med

(2002)

R. Mathiasen et al.

The risk of psychiatric disorders in individuals born prematurely in Denmark from 1974 to 1996

Acta Paediatr

(2011)

R. á Rogvi et al.

Defining smallness for gestational age in the early years of the Danish Medical Birth Registry

PLoS One

(2011)

E-Health TNB of

The National Board of e-Health

(2012)

WHO

ICD-10 classification

(2012)

K. Marsál et al.

Intrauterine growth curves based on ultrasonically estimated foetal weights

Acta Paediatr

(1996)

Sture Holm

A simple sequentially rejective multiple test procedure

Scand J Stat

(1979)

B. Jacobsson et al.

Cerebral palsy and restricted growth status at birth: population-based case–control study

BJOG

(2008)

M.A. Veening

Glucose tolerance, insulin sensitivity, and insulin secretion in children born small for gestational age

J Clin Endocrinol Metab

(2002)

M.J.J. Finken et al.

Preterm birth and later insulin resistance: effects of birth weight and postnatal growth in a population based longitudinal study from birth into adult life

Diabetologia

(2006)

T.M. Van Zeben-van der Aa et al.

Inguinal hernias are common in preterm infants

Arch Dis Child

(1986)

Cited by (16)

Birth Characteristics Among Children Diagnosed with Neurofibromatosis Type 1 and Tuberous Sclerosis
2021, Journal of Pediatrics
Citation Excerpt :
However, some of our analyses were based on small numbers of individuals, particularly for tuberous sclerosis; for this reason, some of the results did not reach statistical significance. Our results regarding NF1 agree with findings reported in a Finnish study9-11 and with data on premature births reported from Denmark.8 Our risk estimates are considerably more precise, being based on approximately 1800 patients with NF1, compared with <500 in each of the 2 other Nordic studies.
To evaluate whether children with neurofibromatosis type 1 (NF1) and tuberous sclerosis have different birth characteristics compared with the general population.
We identified all individuals born in Sweden between 1973 and 2014 from the nationwide Medical Birth Register for whom information on both biological parents was available (n = 4 242 122). Individuals with NF1 and individuals with tuberous sclerosis were identified using data from Swedish population-based health data registers. Using logistic regression models, we assessed the associations between these 2 neurocutaneous syndromes and birth characteristics in a cohort that included 1804 subjects with NF1 and 450 with tuberous sclerosis.
Children with NF1 and tuberous sclerosis were significantly more likely to be born preterm and via cesarean delivery. In addition, children with NF1 were also more likely to be born with other birth characteristics, such as short length, a large head circumference, and a low Apgar score. Moreover, children with NF1 had an increased odds of being born with a high birth weight or large for gestational age (OR, 1.61; 95% CI, 1.42-1.82 and OR, 1.82; 95% CI, 1.60-2.06, respectively).
Children with NF1 and tuberous sclerosis differ from the general population in terms of several birth characteristics, with the strongest associations observed for high birth weight and large for gestational age in individuals with NF1.
Associations of Birth Weight for Gestational Age with Child Health and Neurodevelopment among Term Infants: A Nationwide Japanese Population-Based Study
2020, Journal of Pediatrics
To examine the association of specific Z-score categories of birth weight for gestational age with child health and neurodevelopment using a large nationwide survey in Japan, focusing on term infants.
We included 36 321 children born in 2010. Hospitalization up to 66 months of age was used as an indicator of health status, and responses to questions about age-appropriate behaviors at 30 and 66 months of age were used to indicate neurobehavioral development. We conducted binomial log-linear regression analyses, controlling for child and parental variables. A restricted cubic spline function was used to model the relationship.
Compared with children with birth weight appropriate for gestational age (−1.28 to 1.28 SDs of expected birthweight for gestational age), children who were small for gestational age (SGA) (<−1.28 SD) had higher risks of hospitalization and unfavorable neurobehavioral development, and the risks increased as SGA status became more severe. Compared with the appropriate for gestational age group, the adjusted risk ratios for hospitalization for all causes were 2.5 (95% CI, 1.7-3.6), 1.3 (95% CI, 1.1-1.6), and 1.1 (95% CI, 1.0-1.2) for children who were severely, moderately, and mildly SGA and 1.0 (95% CI, 0.9-1.1), 1.1 (95% CI, 0.9-1.2), and 1.4 (95% CI, 0.9-2.1) for children who were mildly, moderately, and severely large for gestational age, respectively. Severely large for gestational age children also had higher risks of unfavorable neurobehavioral development. These results were supported by spline analyses.
Among term infants, the risks of unfavorable child health and neurodevelopment increased with the severity of SGA.
Maternal urinary tract infection during pregnancy and long-term infectious morbidity of the offspring
2019, Early Human Development
Citation Excerpt :
In addition, we found that UTI in pregnancy was associated with PTD, a correlation already shown by different studies [1,8]. PTD in turn, was recently associated with long-term infectious morbidity [29] and infectious-related hospitalizations [30]. The UTI group had also significantly higher rates of cesarean deliveries, which were associated with increased offspring long-term infectious morbidity [31], so this mode of delivery and all the other characteristics above, were accounted for in the Cox regression model.
Urinary tract infection (UTI) is a common bacterial infection in pregnant women and is associated with adverse perinatal outcomes. We sought to investigate the long-term infectious outcomes of children to mothers who were diagnosed with UTI during their pregnancy.
A population-based cohort analysis was conducted at a single tertiary medical center. The study included all singleton deliveries between the years 1991–2014, comparing offspring born to mothers diagnosed with UTI during their pregnancy with those born to non-exposed mothers. Infectious-related hospitalizations of the offspring up to the age of 18 years were assessed according to a predefined set of ICD-9 codes. A Kaplan-Meier survival curve was conducted to compare cumulative hospitalization incidence between the groups. A Cox regression model was used to adjust for confounders.
During the study period, 243,725 deliveries met the inclusion criteria. Of them, 8034 (3.3%) were exposed to maternal UTI during pregnancy. Infectious-related hospitalizations were significantly prevalent in offspring to exposed mothers (12.3% vs. 11.0%, OR = 1.125, 95% CI 1.051–1.204, Kaplan-Meier log rank p < 0.001). In the Cox regression model, while controlling for clinically relevant confounders, maternal UTI (adjuster HR = 1.240), as well as preterm delivery (adjusted HR = 1.385) and cesarean delivery (adjusted HR = 1.198) were noted as independent risk factors for long-term infectious morbidity of the offspring.
Maternal UTI in pregnancy may influence offspring susceptibility to pediatric infections, as it was found to be an independent risk factor for long-term infectious morbidity of the offspring.
Prematurity Does Not Increase Early Childhood Fracture Risk
2019, Journal of Pediatrics
Citation Excerpt :
In our adjusted analysis, male sex, cholestasis, and PPI exposure during the first year of life were all independently associated with an increased rate of fracture during the first 5 years of life. Our study corroborates the findings of previously published studies suggesting that preterm birth does not confer an increased risk of fracture beyond early infancy.7,11,12,18,19 Dahlenburg et al published a small, retrospective, case-control study of young children presenting with fractures to an acute care clinic; the authors did not find that children who presented with fractures were more likely to have been born preterm than controls.12
To evaluate the impact of prematurity on fracture by age 5, controlling for medications and comorbidities of prematurity.
We performed a retrospective cohort study of infants born in Military Treatment Facilities in 2009-2010 with ≥5 years of follow-up care. Gestational age, low birth weight, comorbidities of prematurity (osteopenia, necrotizing enterocolitis, chronic lung disease, and cholestasis) and fractures were identified by International Classification of Disease, 9th Edition, codes. Pharmaceutical records identified treatment with caffeine, diuretics, postnatal corticosteroids, and antacids. Poisson regression analysis determined fracture rate by 5 years of life.
There were 65 938 infants born in 2009-2010 who received care in the military health system for ≥5 years, including 3589 born preterm; 165 born at ≤28^6/7 weeks of gestation, 380 born at 29-31^6/7 weeks of gestation, and 3044 born at 32-36^6/7 weeks of gestation. Preterm birth at any gestational age was not associated with fracture rate in adjusted models. The fracture rate was increased with cholestasis, proton pump inhibitor exposure, and male sex.
Prematurity was not associated with fracture rate. Neonatal cholestasis and proton pump inhibitor treatment were associated with increased fractures by age 5.
Evidence that children born at early term (37-38 6/7 weeks) are at increased risk for diabetes and obesity-related disorders
2017, American Journal of Obstetrics and Gynecology
Citation Excerpt :
Rates of long-term neurodevelopmental and medical morbidities are higher among survivors of preterm deliveries compared to children born at term.1-4 Prematurity has also been recognized as a risk factor for different metabolic and endocrine disorders in childhood and adolescence including hypothyroidism,5,6 insulin insensitivity,7-9 and overweight and obesity.10 Since fetal hormonal axis development is a continuum,11,12 it may not achieve full maturity in preterm neonates, thus influencing endocrine function later in life.
Prematurity is known to be associated with high rates of endocrine and metabolic complications in the offspring. Offspring born early term (37-38 6/7 weeks’ gestation) were also shown to exhibit long-term morbidity resembling that of late preterm, in several health categories.
We aimed to determine whether early term delivery impacts on the long-term endocrine and metabolic health of the offspring.
A population-based cohort analysis was performed, including all term singleton deliveries occurring from 1991 through 2013 at a single regional tertiary medical center. Congenital malformations and multiple pregnancies were excluded. Gestational age upon delivery was subdivided into early term deliveries and deliveries occurring at full term and later (≥39 weeks’ gestation, comparison group). Endocrine and metabolic morbidity (including diabetes, obesity, hypoglycemia, hyperlipidemia, and hypothyroidism) of the offspring, up to the age of 18 years, was evaluated according to hospitalization files. Kaplan-Meier survival curves were used to compare cumulative morbidity incidence. A Weibull parametric survival model was used to control for time to event, siblings, and other confounders.
During the study period 225,260 term deliveries met the inclusion criteria. Of them, 24% (n = 54,073) occurred at early term. Endocrine and metabolic morbidity was significantly more common in the early term group (0.51% vs 0.41%, P = .003). Specifically, overweight and obesity were more common among the early term group (P = .002). Differences were more prominent among children >5 years, who exhibited higher rates of type 1 diabetes mellitus, as well as obesity, when born at early term (P < .05). The survival curves demonstrated higher cumulative incidence of total endocrine and metabolic morbidity in the early term group. Using the Weibull parametric survival model, while controlling for siblings, maternal diabetes, hypertension, labor induction, and Apgar score, early term delivery exhibited an independent association with long-term childhood endocrine and metabolic morbidity of the offspring (adjusted hazard ratio, 1.17; 95% confidence interval, 1.01–1.34) and more so for age >5 years (adjusted hazard ratio, 1.30; 95% confidence interval, 1.08–1.56).
Deliveries occurring at early term are associated with higher rates of long-term pediatric endocrine and metabolic morbidity of the offspring as compared with deliveries occurring at a later gestational age. This association may be due to absence of full maturity of the hormonal axis in early term neonates or, alternatively, suggest an underlying fetal endocrine dysfunction as the initial mechanism responsible for spontaneous early term delivery.
Neonatal outcomes according to different therapies for gestational diabetes mellitus
2017, Jornal de Pediatria
Citation Excerpt :
The percentage of cesarean deliveries in the study was 52.1%. This is similar to the percentage of cesarean sections in other Brazilian studies,24,25 but rates are lower in the international scenario.6,26 This difference may be due to the dissemination of cesarean practice in Brazil, unlike other countries.
To compare different neonatal outcomes according to the different types of treatments used in the management of gestational diabetes mellitus.
This was a retrospective cohort study. The study population comprised pregnant women with gestational diabetes treated at a public maternity hospital from July 2010 to August 2014. The study included women aged at least 18 years, with a singleton pregnancy, who met the criteria for gestational diabetes mellitus. Blood glucose levels, fetal abdominal circumference, body mass index and gestational age were considered for treatment decision-making. The evaluated neonatal outcomes were: type of delivery, prematurity, weight in relation to gestational age, Apgar at 1 and 5 min, and need for intensive care unit admission.
The sample consisted of 705 pregnant women. The neonatal outcomes were analyzed based on the treatment received. Women treated with metformin were less likely to have children who were small for gestational age (95% CI: 0.09–0.66) and more likely to have a newborn adequate for gestational age (95% CI: 1.12–3.94). Those women treated with insulin had a lower chance of having a preterm child (95% CI: 0.02–0.78). The combined treatment with insulin and metformin resulted in higher chance for a neonate to be born large for gestational age (95% CI: 1.14–11.15) and lower chance to be born preterm (95% CI: 0.01–0.71). The type of treatment did not affect the mode of delivery, Apgar score, and intensive care unit admission.
The pediatrician in the delivery room can expect different outcomes for diabetic mothers based on the treatment received.
Comparar diferentes desfechos neonatais de acordo com as diferentes modalidades de tratamentos do diabetes mellitus gestacional.
Trata-se de uma coorte retrospectiva. A população do estudo foi composta por gestantes com diabetes gestacional atendidas em uma maternidade pública desde Julho de 2010 a Agosto de 2014. Foram incluídas mulheres com idade mínima de 18 anos, gestação única e com critérios para diabetes mellitus gestacional. Para decisão terapêutica foram considerados glicemias, circunferência abdominal fetal, índice de massa corporal e idade gestacional. Os desfechos neonatais avaliados foram: via de parto, prematuridade, relação do peso com idade gestacional, Apgar no 1° e 5° minuto e necessidade de internação em unidade de terapia intensiva.
A amostra foi composta por 705 gestantes. Os desfechos neonatais foram analisados com base na terapêutica recebida. Mulheres tratadas com metformina tiveram menor chance de terem filhos pequenos para a idade gestacional (IC 95%: 0,09-0,66) e maior chance de terem um filho adequado para a idade gestacional (IC 95%: 1,12-3,94). A gestante tratada com insulina teve menor chance de ter um filho prematuro (IC 95%: 0,02-0,78). O tratamento feito com a associação de insulina e metformina resultou em maior chance de um recém-nascido grande para a idade gestacional (IC 95%: 1,14-11,15) e menor chance de prematuridade (IC 95%: 0,01-0,71). A modalidade de tratamento não interferiu na via de parto, Apgar e internação em terapia intensiva.
O pediatra na sala de parto pode esperar diferentes desfechos para o filho de mãe diabética, com base no tratamento recebido.

View all citing articles on Scopus

View full text

Prematurity, smallness-for-gestational age and later hospital admissions: A nation-wide registry study

Highlights

Abstract

Introduction

Methods

Results

Conclusion

Introduction

Section snippets

Data

Ethics

Statistical analysis

Results

Discussion

Conflicts of interest

Lancet

Am J Obstet Gynecol

Obstet Gynecol

Am J Obstet Gynecol

Early Hum Dev

Lancet

Ophthalmology

J Pediatr

Epilepsy Res

J Clin Epidemiol

J Clin Epidemiol

Respir Med

Birth weight in relation to morbidity and mortality among newborn infants

N Engl J Med

The developmental origins of adult disease (Barker) hypothesis

Aust N Z J Obstet Gynaecol

A woman's own birth weight and gestational age predict her later risk of developing preeclampsia, a precursor of chronic disease

Epidemiology

Women born preterm or with inappropriate weight for gestational age are at risk of subsequent gestational diabetes and pre-eclampsia

PLoS One

Neonatal risk factors for cerebral palsy in very preterm babies: case–control study

BMJ

Understanding retinopathy of prematurity: update on pathogenesis

Neonatology

Pathogenesis and prevention of necrotizing enterocolitis

Curr Opin Infect Dis

Long-term metabolic consequences of being born small for gestational age

Pediatr Diabetes

Size at birth as a predictor of mortality in adulthood: a follow-up of 350 000 person-years

Int J Epidemiol

Outcomes in young adulthood for very-low-birth-weight infants

N Engl J Med

The risk of psychiatric disorders in individuals born prematurely in Denmark from 1974 to 1996

Acta Paediatr

Defining smallness for gestational age in the early years of the Danish Medical Birth Registry

PLoS One

The National Board of e-Health

ICD-10 classification

Intrauterine growth curves based on ultrasonically estimated foetal weights

Acta Paediatr

A simple sequentially rejective multiple test procedure

Scand J Stat

Cerebral palsy and restricted growth status at birth: population-based case–control study

BJOG

Glucose tolerance, insulin sensitivity, and insulin secretion in children born small for gestational age

J Clin Endocrinol Metab

Preterm birth and later insulin resistance: effects of birth weight and postnatal growth in a population based longitudinal study from birth into adult life

Diabetologia

Inguinal hernias are common in preterm infants

Arch Dis Child