Late Term Birth Research Articles

Neonatal Outcomes of Early Term Versus Late-Term Births in a University Teaching Hospital in Lagos, Nigeria.

There is increasing evidence of an association between early term birth and adverse neonatal outcomes. However, there is a paucity of data on the true neonatal outcomes following term deliveries in lower-income countries, including Nigeria. This study compared the neonatal outcomes of early and late-term deliveries in a tertiary hospital in Lagos, Nigeria. This was a five-year retrospective cohort study of all term deliveries between January 2013 and December 2017. Data were obtained from the labour ward and neonatal ward admission registers and medical records of the hospital.Descriptive and inferential statistics were computed for all relevant data. Statistical significance was reported at a p-value < 0.05. Of the 1,001 deliveries reviewed and analysed for this study, 215 recorded adverse neonatal events, with a significantly higher proportion of these occurring in early term compared to late-term delivered pregnancies (75.8% versus 24.2%, p < 0.001).There was a statistically higher rate of NICU admission in early term neonates than in late-term neonates (14.3 versus 3.9%, p < 0.001). Respiratory complications were the most common adverse outcomes experienced by neonates in both groups. However, the early term neonates had a higher risk even when adjusted for sex, birth weight, and mode of delivery. Our study highlights the substantial impact of gestational age on neonatal outcomes, with early term neonates at a significantly higher risk of adverse events compared to late-term neonates. Strategies aimed at reducing the rates of elective early term induction of labour and caesarean deliveries may help minimize the occurrence of adverse neonatal outcomes in our setting.

Association of maternal education, neighborhood deprivation, and racial segregation with gestational age at birth by maternal race/ethnicity and United States Census region in the ECHO cohorts.

In the United States, disparities in gestational age at birth by maternal race, ethnicity, and geography are theorized to be related, in part, to differences in individual- and neighborhood-level socioeconomic status (SES). Yet, few studies have examined their combined effects or whether associations vary by maternal race and ethnicity and United States Census region. We assembled data from 34 cohorts in the Environmental influences on Child Health Outcomes (ECHO) program representing 10,304 participants who delivered a liveborn, singleton infant from 2000 through 2019. We investigated the combined associations of maternal education level, neighborhood deprivation index (NDI), and Index of Concentration at the Extremes for racial residential segregation (ICERace) on gestational weeks at birth using linear regression and on gestational age at birth categories (preterm, early term, post-late term relative to full term) using multinomial logistic regression. After adjustment for NDI and ICERace, gestational weeks at birth was significantly lower among those with a high school diploma or less (-0.31 weeks, 95% CI: -0.44, -0.18), and some college (-0.30 weeks, 95% CI: -0.42, -0.18) relative to a master's degree or higher. Those with a high school diploma or less also had an increased odds of preterm (aOR 1.59, 95% CI: 1.20, 2.10) and early term birth (aOR 1.26, 95% CI: 1.05, 1.51). In adjusted models, NDI quartile and ICERace quartile were not associated with gestational weeks at birth. However, higher NDI quartile (most deprived) associated with an increased odds of early term and late term birth, and lower ICERace quartile (least racially privileged) associated with a decreased odds of late or post-term birth. When stratifying by region, gestational weeks at birth was lower among those with a high school education or less and some college only among those living in the Northeast or Midwest. When stratifying by race and ethnicity, gestational weeks at birth was lower among those with a high school education or less only for the non-Hispanic White category. In this study, maternal education was consistently associated with shorter duration of pregnancy and increased odds of preterm birth, including in models adjusted for NDI and ICERace.

Risk of stillbirth in singleton fetuses with advancing gestational age at term: A 10-year experience of late third trimester prenatal screenings of 50,000 deliveries in a referral center in northern Italy.

The risk of intrauterine death (IUD) at term varies from less than one to up to three cases per 1,000 ongoing pregnancies. The cause of death is often largely undefined. Protocols and criteria to prevent and define the rates and causes of stillbirth are the subjects of important scientific and clinical debates. We examined the gestational age and rate of stillbirth at term in a 10-year period at our maternity hub to evaluate the possible favorable impact of a surveillance protocol on maternal and fetal well-being and growth. Our cohort included all women with singleton pregnancies resulting in early term to late term birth at our maternity hub between 2010 and 2020, with the exclusion of fetal anomalies. As per our protocol for monitoring term pregnancies, all women underwent near term to early term maternal and fetal well-being and growth surveillance. If risk factors were identified, outpatient monitoring was initiated and early- or full-term induction was indicated. Labor was induced at late term (41+0-41+4 weeks of gestation), if it did not occur spontaneously. We retrospectively collected, verified, and analyzed all cases of stillbirth at term. The incidence of stillbirth at each week of gestation, was calculated by dividing the number of stillbirths observed that week by the number of women with ongoing pregnancies in that same week. The overall rate of stillbirth per 1000 was also calculated for the entire cohort. Fetal and maternal variables were analyzed to assess the possible causes of death. A total of 57,561 women were included in our study, of which 28 cases of stillbirth (overall rate, 0.48 per 1000 ongoing pregnancies; 95% CI: 0.30-0.70) were identified. The incidence of stillbirth in the ongoing pregnancies measured at 37, 38, 39, 40, and 41 weeks of gestation was 0.16, 0.30, 0.11, 0.29, and 0.0 per 1000, respectively. Only three cases occurred after 40+0 weeks of gestation. Six patients had an undetected small for gestational age fetus. The identified causes included placental conditions (n = 8), umbilical cord conditions (n = 7), and chorioamnionitis (n = 4). Furthermore, the cases of stillbirth included one undetected fetal abnormality (n = 1). The cause of fetal death remained unknown in eight cases. In a referral center with an active universal screening protocol for maternal and fetal prenatal surveillance at near and early term, the rate of stillbirth was 0.48 per 1000 in singleton pregnancies at term in a large, unselected population. The highest incidence of stillbirth was observed at 38 weeks of gestation. The vast majority of stillbirth cases occurred before 39 weeks of gestation and 6 of 28 cases were SGA, and the median percentile of the remaining case was the 35th.

The Incidence and Outcomes of Late-Term Pregnancy.

Little is known about the outcomes of late-term pregnancy. In this study, we aim to assess the incidence and adverse prenatal outcomes associated with late-term pregnancy. We retrospectively assessed all singleton pregnant mothers who gave birth at Khalij-e-Fars Hospital in Bandar Abbas, Iran, between January 2020 and 2022. All preterm and post-term deliveries were excluded. Mothers were divided into two groups: late-term mothers (41 0/7-41 6/7 weeks of gestation) and term mothers (37 0/7-40 6/7 weeks of gestation). Demographic factors, obstetricfactors, maternal comorbidities, and prenatal outcomes were extracted from the electronic data of each mother. The incidence of late-term births was calculated. The chi-squared test was used to compare differences between the groups. Logistic regression models were used to assess the association of prenatal outcome with late-term pregnancy. There were 8,888 singleton deliveries during the study period, and 1,269 preterm and post-term pregnancies were ruled out. Of the 7,619 deliveries, 309 (4.1%) were late-term, while 7,310 (95.9%) were term. There were no sociodemographic differences between term and late-term mothers. The late-term group had a higher prevalence of primiparous mothers, and the term group had a higher prevalence of diabetes. Late-term mothers had a higher risk of macrosomia (adjusted odds ratio (aOR): 2.24 (95% confidence interval (CI): 1.34-3.01)), meconium amniotic fluid (aOR: 2.32 (95% CI: 1.59-3.14)), and fetal distress (aOR: 2.38 (95% CI: 1.54-2.79)). When compared to term pregnancy, the risk of low birth weight (LBW) was lower in late-term pregnancy (aOR: 0.69 (95% CI: 0.36-0.81)). Late-term pregnancy was found to be more likely to be associated with macrosomia, meconium amniotic fluid, and fetal distress, but serious maternal and neonatal adverse events were comparable to term pregnancy.

Population birth outcomes in 2020 and experiences of expectant mothers during the COVID-19 pandemic: A 'born in Wales' mixed methods study using routine data.

Pregnancy can be a stressful time and the COVID-19 pandemic has affected all aspects of life. This study aims to investigate the pandemic impact on pregnancy experience, rates of primary childhood immunisations and the differences in birth outcomes in during 2020 to those of previous years. Self-reported pregnancy experience: 215 expectant mothers (aged 16+) in Wales completed an online survey about their experiences of pregnancy during the pandemic. The qualitative survey data was analysed using codebook thematic analysis. Population-level birth outcomes in Wales: Stillbirths, prematurity, birth weight and Caesarean section births before (2016-2019) and during (2020) the pandemic were compared using anonymised individual-level, population-scale routine data held in the Secure Anonymised Information Linkage (SAIL) Databank. Uptake of the first three scheduled primary childhood immunisations were compared between 2019 and 2020. The pandemic had a negative impact on the mental health of 71% of survey respondents, who reported anxiety, stress and loneliness; this was associated with attending scans without their partner, giving birth alone, and minimal contact with midwives. There was no significant difference in annual outcomes including gestation and birth weight, stillbirths, and Caesarean sections for infants born in 2020 compared to 2016-2019. There was an increase in late term births (≥42 weeks gestation) during the first lockdown (OR: 1.28, p = 0.019) and a decrease in moderate to late preterm births (32-36 weeks gestation) during the second lockdown (OR: 0.74, p = 0.001). Fewer babies were born in 2020 (N = 29,031) compared to 2016-2019 (average N = 32,582). All babies received their immunisations in 2020, but there were minor delays in the timings of immunisations. Those due at 8-weeks were 8% less likely to be on time (within 28-days) and at 16-weeks, they were 19% less likely to be on time. Whilst the pandemic had a negative impact on mothers' experiences of pregnancy. Population-level data suggests that this did not translate to adverse birth outcomes for babies born during the pandemic.

Population birth outcomes and experiences of expectant mothers during the COVID-19 pandemic in Wales: a mixed methods study

BackgroundPregnancy can be a stressful time and the COVID-19 pandemic is thought to have heightened maternal stress. This study aimed to investigate the effect of the COVID-19 pandemic on population birth outcomes, uptake of primary immunisations, and expectant mothers' experiences of pregnancy in Wales. MethodsIn this mixed methods study we analysed stillbirths, prematurity, birthweight and caesarean section births before (2016–19) and during (2020) the pandemic using national routine anonymised data held in the Secure Anonymised Information Linkage Databank. Uptake of the first three scheduled primary immunisations were compared between 2019 and 2020. Immunisations were extracted from the routinely collected data in the National Community Child Health Database. We compared percentages between years the ran χ2 with Yates correction for the three percentages given. Expectant mothers (aged ≥16 years) in Wales completed an online survey about their experiences of pregnancy during the pandemic. Inclusion criteria was being aged 16 years or older and living in Wales. The qualitative survey data was analysed using codebook thematic analysis. Ethical approval was granted by Swansea University Ethics Committee and each participant provided written consent before answering any survey questions. FindingsThere was no significant difference between annual outcomes including gestation and birthweight, stillbirths, and caesarean sections for infants born in 2020 compared with 2016–19. Difference in gestation (moderate to late preterm difference –0·26%, 95% CI –0·52% to –0·01%). Difference in low birthweight 0·13% (0·00% to 0·26%). Difference in stillbirths –0·01% (–0·02% to 0·00%). Difference in caesarean sections –0·42% (–1·13% to 0·29%). There was an increase in late-term births (≥42 weeks gestation) during the first lockdown (odds ratio [OR] 1·28, p=0·019) and a decrease in moderate to late preterm births (32–36 weeks gestation) during the second lockdown (OR 0·74, p=0·001). Fewer babies were born in 2020 (n=29 031) compared with 2016–19 (n=32 582; mean [SD 1561]). All babies received their immunisations in 2020, but there were minor delays in the timings of vaccines. Those vaccinations due at 8-weeks were 8% less likely to be on time (within 28 days) and, at 16-weeks, they were 19% less likely to be on time. The pandemic had a negative effect on the mental health of 151 (72%) of 211 survey respondents, who reported feeling anxious, nervous, or depressed; this finding was associated with attending scans without their partner, giving birth alone, and minimal contact with midwives. InterpretationThe COVID-19 pandemic had a negative effect on mothers' experiences of pregnancy; however, population data suggests that this did not translate to adverse birth outcomes for babies born during the pandemic. FundingHealth Care Research Wales

Bayesian EMAX model with a mixture of normal distributions for dose–response in clinical trials

When a dose–response relationship is monotonic, the EMAX model has been shown to provide a good empirical fit for designing and analyzing dose–response data across a wide range of pharmaceutical studies. However, the EMAX model has never been applied to a finite mixture distribution. Motivated by a proposal investigating DHA dose effect on preterm birth (PTB, <37 weeks gestation) rate, we developed a Bayesian EMAX mixture model incorporating the three normal components finite mixture model into the EMAX framework. The proposed Bayesian EMAX mixture model analyzes gestational age as a continuous variable, which allows for statistically efficient estimates of PTB rate using various cut point with the same parsimonious model. For example, we can estimate the rate of early PTB (ePTB, <34 weeks gestation), PTB (<37 weeks gestation), and late-term birth (>41 weeks gestation) using the same model. We compared our proposed EMAX mixture model with an EMAX logistic model and an independent doses logistic model for a dichotomized endpoint using extensive simulations. Across the scenarios under consideration, the EMAX mixture model achieved higher power than the EMAX logistic model and the independent doses logistic model in detecting the effect of DHA supplementation on the PTB rate. The EMAX mixture model also resulted in smaller mean squared errors (MSE) in PTB rate estimates.

Comparison of stillbirth trends over two decades in Wales, United Kingdom and Western Australia: An international retrospective cohort study.

Stillbirth is a critical public health issue worldwide. While the rates in high-income countries are relatively low, there are persistent between-country disparities. To compare stillbirth rates and trends in Wales and the State of Western Australia (WA), Australia, and provide insights into any differences. In this international retrospective cohort study, we pooled population-based data collections of all births ≥24weeks' gestation (excluding terminations for congenital anomalies) between 1993 and 2015, divided into six time periods. The stillbirth rate per 1000 births was estimated for each cohort in each time period. Multivariable Poisson regression analyses, adjusted for appropriateness of growth, socio-economic status, maternal age, and multiple birth, were performed to evaluate the interaction between cohort and time period. Relative risk (RR) and 95% confidence interval (CI) for each time period and cohort were calculated. There were 767731 births (3725 stillbirths) in Wales and 648373 (2431 stillbirths) in WA. The overall stillbirth rate declined by 15.9% over the study period in Wales (from 5.3 in 1993-96 to 4.5 per 1000 births in 2013-15; Ptrend <.01) but by 40.4% in WA (from 4.9 to 2.9 per 1000 births in WA; Ptrend <.01). Using 1993-96 in WA as the reference group, the adjusted RRs for stillbirths at 37-38weeks' gestation in the most recent study period (2013-15) were 0.85 (95% CI 0.64, 1.13) in Wales and 0.51 (95% CI 0.36, 0.73) in WA. The stillbirth rates between Wales and WA have widened in the last two decades (especially among late-term births), although the absolute rates for both are distinctly higher than the best-performing nations. While the differences may be partly explained by timing of birth and maternal life style behaviours such as smoking, it is important to identify and ameliorate the associated risk factors to support a reduction in preventable stillbirths.

Risk of preterm birth in a twin pregnancy after an early-term birth in the preceding singleton pregnancy: a retrospective cohort study.

To evaluate whether a history of spontaneous early-term birth (37+0 -38+6 weeks of gestation) in the previous singleton pregnancy is a risk factor for preterm birth (PTB) in a subsequent twin pregnancy. Retrospective cohort study. Two French university hospitals (2006-2016). All women who delivered twins from 24+0 weeks after a preceding singleton pregnancy birth at 37+0 to 41+6 weeks. Multivariate logistic regression analysis of association between twin PTB and a previous spontaneous singleton early-term birth. Twin PTB rate before 37, 34 and 32weeks of gestation. Among 618 twin pregnancies, 270 were born preterm, 92 of them with a preceding spontaneous singleton early-term birth. The univariate analysis showed a significantly higher risk of twin PTB before 37, 34 and 32weeks among those 92 women compared with those with a full- or late-term birth in their previous singleton pregnancy. This association remained significant after logistic regression (odds ratio [OR] between 2.42 and 3.88). The secondary analysis, restricted to the twin pregnancies with spontaneous PTB found similar results, with a risk of PTB before 37, 34 and 32weeks significantly higher among women with a previous spontaneous singleton early-term birth, including after logistic regression analysis (OR between 3.51 and 3.56). A preceding spontaneous singleton early-term birth is a strong and easily identified risk factor for PTB in twin pregnancies. Spontaneous 'early-term' birth of a singleton is a significant risk factor for future preterm births in twin pregnancies.

Impact of continuous electronic fetal monitoring on birth outcomes in low-risk pregnancies.

Continuous electronic fetal monitoring (CEFM) is a standard of hospital care during the intrapartum period. We investigated its use on childbirth outcomes in low-risk pregnancies, and examined whether outcomes differed by gestational age within a term pregnancy. A retrospective secondary data analysis using birth registry data from two diverse northeastern US states from 1992 to 2014. Chi-square test and the Fisher exact tests were used to examine associations between CEFM and childbirth outcomes. Multivariable Poisson regression models were used to estimate risk ratios of childbirth outcomes related to CEFM use, adjusting for potential confounders. Use of CEFM was independently associated with a 10% (State 1) and 40% (State 2) increased risk for primary cesarean delivery and an increased risk for assisted vaginal births (14% and 24%, respectively) after adjustment for confounders. CEFM use was not associated with reduced risk for infant mortality (neonatal mortality, 0-27days, and post-neonatal mortality, 28-364days) in term births (37-41weeks' gestation). After stratifying term pregnancies into early term, full term, and late term, use of CEFM was associated with reduced risk for neonatal mortality in early-term births (37 0/7weeks' to 38 6/7weeks' gestation) in State 2 (RR 0.44 [95% CI 0.21-0.92]), but not in State 1. There was no association between CEFM use and infant mortality (neonatal and post-neonatal) in full-term or late-term births. The study results do not support universal use of CEFM in pregnancies that are low-risk and at term.

RhoA and Rho-kinase inhibitors modulate cervical resistance: The possible role of RhoA/Rho-kinase signalling pathway in cervical ripening and contractility

Improper cervical function may lead premature or late-term birth. The RhoA/Rho-kinase (ROCK) signalling pathway takes part in cellular functions including smooth muscle contraction. No information is available about the cervical expression of the RhoA/ROCK system during pregnancy. Our aim was to detect the mRNA and protein expression of ROCK enzymes in rat cervices and to evaluate the effects of RhoA/ROCK inhibitors on cervical resistance.The mRNA and protein expressions of RhoA, ROCK I and II were measured in non-pregnant, pregnant and postpartum rat cervices and during parturition by Real-time qPCR and Western blot. The cervical resistance modifying effects of RhoA (simvastatin) and ROCK (fasudil, Y-27632) (10−6M) were investigated in tissue bath experiments.RhoA mRNA was increased on post-partum day 3, while the RhoA protein expression was decreased near and during parturition. ROCK I mRNA and protein expressions were fluctuating with a decrease in protein expression during parturition. ROCK II mRNA and protein expressions were sharply reduced during parturition. Simvastatin increased the cervical resistance on pregnancy days 20 and 22 while Y-27632 and fasudil reduced the resistance on pregnancy days 20.The decrease in RhoA/ROCK expression near parturition may take part in cervical ripening, especially in the final processes leading to delivery. ROCK inhibitors might be potential drug candidates to treat insufficient cervical ripening late-term pregnancies. The effect of simvastatin possibly due to its unique smooth muscle contracting activity in pregnant cervix. Compounds with simvastatin-like action might be new drug candidates for preterm cervical ripening.

Relationship between maternal exposure to bisphenol S and pregnancy duration

Bisphenol S (BPS) has been progressively used due to the potential safety problems of bisphenol A (BPA). Thus Human studies are needed to investigate the developmental effects of BPS. In this study, the impact of maternal BPS exposure on birth outcomes was evaluated with linear and logistic regression models. BPS was analyzed in spot urine samples collected from 985 pregnant women at admission to labor. It was found in 93.7% of the urine samples with the specific gravity adjusted geometric mean concentration of 0.17 μg/L. One ln-unit increase in urinary BPS was associated with a 0.72-day increase in pregnancy duration (95% CI: 0.34, 1.09). When stratified by fetal sex, each ln-unit increase in maternal urinary BPS was significantly correlated with increased gestational age [adjusted β = 1.02, 95% confidence intervals (CI): 0.47, 1.57] and increased odds of late term birth [adjusted odds ratio = 1.29, 95% CI: 1.00, 1.67] for girls, but not significantly for boys. Including maternal urinary BPA and BPS in one model did not change the results. Associations of BPS with birth weight or length were not observed. This is the first report about BPS exposure for pregnant women from China. Higher maternal urinary BPS concentrations were associated with increased gestational age, suggesting maternal BPS exposure may interfere with pregnancy duration. The findings require replication but reveal the probable risks posed by the developmental BPS exposure.

Urinary level of triclosan in a population of Chinese pregnant women and its association with birth outcomes

Triclosan (TCS) is a suspected endocrine disrupting chemical which is widely used in consumer products as an antibacterial agent. But findings in human studies focusing on the fetal developmental effects of prenatal TCS exposure were rare and inconsistent. This study aimed to determine maternal urinary TCS and investigate its association with birth outcomes. Pregnant women (n=1006) were randomly selected from the prospective Healthy Baby Cohort (HBC) enrolled in 2014. TCS levels were determined in maternal urine samples collected at delivery and recorded birth outcomes were obtained from the medical records. Multiple linear regressions were applied to evaluate associations of maternal urinary TCS levels with birth outcomes including birth weight, birth length, and gestational age. Logistic regressions were used to evaluate associations with preterm birth, late term birth, and low birth weight. The geometric mean concentrations for TCS and specific gravity (SG) adjusted TCS in maternal urines were 0.73, 0.78ng/mL, respectively. In the crude model, one ln-unit increase of urinary SG-adjusted TCS concentration was associated with a 0.30-day [95% confidence interval (CI): 0.00, 0.60] increase in gestational age; however, the associations were not statistically significant after adjustment for covariates. No significant associations of SG-adjusted TCS concentrations with birth weight and birth length were observed. Maternal SG-adjusted TCS concentrations were not related to preterm birth, late term birth, and low birth weight (all p>0.10). Our findings reported a relatively low level of TCS among Chinese pregnant women. With such exposure level, we did not find strong evidence for associations between maternal TCS exposure and birth outcomes. Longitudinal studies concerning about different potential effects of TCS on perinatal health are necessary.

Inter-hospital variations in labor induction and outcomes for nullipara: an Australian population-based linkage study.

This study aimed to describe variation in inter-hospital induction of labor (IOL) rates, determine whether variation is explained by individual and hospital factors and examine birth outcomes. Nullipara at term with a singleton cephalic birth were identified using linked hospital discharge and birth data for 66 hospitals in New South Wales, Australia, 2010-2011. Random effects multilevel logistic regression models were fitted for early term, full term, and late term births, adjusting for individual and hospital factors. Hospital intrapartum cesarean rates, and severe maternal and neonatal morbidity outcomes were determined according to hospital IOL rate. Of 69 549 nullipara, 24 673 (35%) had an IOL. For early term births, adjusted hospital IOL (aIOL) rates varied (3.3-13.9%), with 11 of 66 (17%) hospitals having aIOL rates significantly different from the average aIOL rate. For births at full term, the hospital aIOL rates varied (10.6-32.6%), with 29 hospitals (44%) having aIOL rates significantly different from the average aIOL rate. For late term births, the hospital aIOL rates varied (45.1-67.5%), with 11 hospitals (17%) having aIOL rates significantly different from the overall average aIOL rate for women with late term births. There was generally no relationship between higher or lower hospital IOL rates and intrapartum cesarean section rates, or maternal or neonatal adverse outcomes. Inter-hospital IOL rates for nullipara with a singleton cephalic term birth had high unexplained variation, with no clear association with intrapartum cesarean section rates, or maternal or neonatal adverse outcomes.

Gestational Age, Birthweight for Gestational Age, and Childhood Hospitalisations for Asthma and Other Wheezing Disorders

Preterm birth, early term birth, and low birthweight are associated with childhood wheezing disorders in developed Western settings, but observed associations could be confounded by socio-economic position. This study aims to clarify such associations in a developed non-Western setting with a different confounding structure. Using Cox regression, we examined the adjusted associations of gestational age and birthweight for gestational age with time to first public hospital admission for asthma, bronchitis, and bronchiolitis (International Classification of Diseases, Ninth Version Clinical Modification 466, 490, and 493) from 9 days to 12 years in a population-representative birth cohort of 8327 Chinese children in Hong Kong, a developed setting with less clear social patterning of prematurity or birthweight. Analyses were adjusted for infant and parental characteristics and socio-economic position. Children born late preterm (34 to <37 weeks) had higher risk of hospitalisation for asthma and other wheezing disorders [hazard ratio (HR) 1.99, 95% confidence interval (CI) 1.48, 2.67] than children born full term (39 to <41 weeks). Early term births (37 to <39 weeks) had HR 1.01 (95% CI 0.84, 1.22), late term births (41 to <42 weeks) had HR 0.77 (95% 0.59, 1.01), and post-term births (≥42 weeks) had HR 0.56 (95% CI 0.32, 0.98). Large for gestational age was associated with lower risk of hospitalisation (HR 0.76, 95% CI 0.57, 0.99). The association of preterm birth with childhood wheezing could be biologically mediated. We cannot rule out an association for early term births.