Routinely collected English birth data sets: comparisons and recommendations for reproductive epidemiology

Emergency Maternal Hospital Readmissions in the Postnatal Period: A Population-Based Cohort Study

OBJECTIVE

To determine the change in English emergency postnatal maternal readmissions 2007-2017 (pre-COVID-19) and the association with maternal demographics, obstetric risk factors and postnatal length of stay (LOS).

DESIGN

National cohort study.

SETTING

All English National Health Service hospitals.

POPULATION

A total of 6 192 140 women who gave birth in English NHS hospitals from April 2007 to March 2017.

METHODS

Statistical analysis using birth and readmission data from routinely collected National Hospital Episode Statistics (HES) database.

MAIN OUTCOME MEASURES

Rate of emergency postnatal maternal hospital readmissions related to pregnancy or giving birth within 42 days postpartum, readmission diagnoses and association with maternal demographic factors, obstetric risk factors and postnatal LOS.

RESULTS

A significant increase in the rate of emergency postnatal maternal readmissions from 15 128 (2.5%) in 2008 to 20 734 (3.4%) in 2016 (aOR 1.32, 95% CI 1.28-1.37) was found. Risk factors for readmission included minoritised ethnicity (particularly Black or Black British ethnicity: aOR 1.35, 95% CI 1.31-1.39); age < 20 years (aOR 1.09, 95% CI 1.05-1.12); 40+ years (aOR 1.07, 95% CI 1.03-1.10); primiparity (multiparity: aOR 0.92, 95% CI 0.91-0.93); nonspontaneous vaginal birth modes (emergency caesarean: aOR 1.86, 95% CI 1.82-1.90); longer LOS (4+ vs. 0 days: aOR 1.58, 95% CI 1.53-1.64); and obstetric risk factors including urinary retention (aOR 2.34, 95% CI 2.06-2.53) and postnatal wound breakdown (aOR 2.01, 95% CI 1.83-2.21).

CONCLUSIONS

The concerning rise in emergency maternal readmissions should be addressed from a health inequalities perspective focusing on women from minoritised ethnic groups; those <20 and ≥40 years old; primiparous women; and those with specified obstetric risk factors.

Risks of adverse obstetric outcomes among female survivors of adolescent and young adult cancer in England (TYACSS): a population-based, retrospective cohort study

BACKGROUND

There are limited data on the risks of obstetric complications among survivors of adolescent and young adult cancer with most previous studies only reporting risks for all types of cancers combined. The aim of this study was to quantify deficits in birth rates and risks of obstetric complications for female survivors of 17 specific types of adolescent and young adult cancer.

METHODS

The Teenage and Young Adult Cancer Survivor Study (TYACSS)-a retrospective, population-based cohort of 200 945 5-year survivors of cancer diagnosed at age 15-39 years from England and Wales-was linked to the English Hospital Episode Statistics (HES) database from April 1, 1997, to March 31, 2022. The cohort included 17 different types of adolescent and young adult cancers. We ascertained 27 specific obstetric complications through HES among 96 947 women in the TYACSS cohort. Observed and expected numbers for births and obstetric complications were compared between the study cohort and the general population of England to identify survivors of adolescent and young adult cancer at a heighted risk of birth deficits and obstetric complications relative to the general population.

FINDINGS

Between April 1, 1997, and March 31, 2022, 21 437 births were observed among 13 886 female survivors of adolescent and young adult cancer from England, which was lower than expected (observed-to-expected ratio: 0·68, 95% CI 0·67-0·69). Other survivors of genitourinary, cervical, and breast cancer had under 50% of expected births. Focusing on more common (observed ≥100) obstetric complications that were at least moderately in excess (observed-to-expected ratio ≥1·25), survivors of cervical cancer were at risk of malpresentation of fetus, obstructed labour, amniotic fluid and membranes disorders, premature rupture of membranes, preterm birth, placental disorders including placenta praevia, and antepartum haemorrhage. Survivors of leukaemia were at risk of preterm delivery, obstructed labour, postpartum haemorrhage, and retained placenta. Survivors of all other specific cancers had no more than two obstetric complications that exceeded an observed-to-expected ratio of 1·25 or greater.

INTERPRETATION

Survivors of cervical cancer and leukaemia are at risk of several serious obstetric complications; therefore, any pregnancy should be considered high-risk and would benefit from obstetrician-led antenatal care. Despite observing deficits in birth rates across all 17 different types of adolescent and young adult cancer, we provide reassurance for almost all survivors of adolescent and young adult cancer concerning their risk of almost all obstetric complications. Our results provide evidence for the development of clinical guidelines relating to counselling and surveillance of obstetrical risk for female survivors of adolescent and young adult cancer.

FUNDING

Children with Cancer UK, The Brain Tumour Charity, and Academy of Medical Sciences.

Induction of labour at 39 weeks and adverse outcomes in low-risk pregnancies according to ethnicity, socioeconomic deprivation, and parity: A national cohort study in England

BACKGROUND

Ethnic and socioeconomic inequalities in obstetric outcomes are well established. However, the role of induction of labour (IOL) to reduce these inequalities is controversial, in part due to insufficient evidence. This national cohort study aimed to identify adverse perinatal outcomes associated with IOL with birth at 39 weeks of gestation ("IOL group") compared to expectant management ("expectant management group") according to maternal characteristics in women with low-risk pregnancies.

METHODS AND FINDINGS

All English National Health Service (NHS) hospital births between January 2018 and March 2021 were examined. Using the Hospital Episode Statistics (HES) dataset, maternal and neonatal data (demographic, diagnoses, procedures, labour, and birth details) were linked, with neonatal mortality data from the Office for National Statistics (ONS). Women with a low-risk pregnancy were identified by excluding pregnancies with preexisting comorbidities, previous cesarean section, breech presentation, placenta previa, gestational diabetes, or a baby with congenital abnormalities. Women with premature rupture of membranes, placental abruption, hypertensive disorders of pregnancy, amniotic fluid abnormalities, or antepartum stillbirth were excluded only from the IOL group. Adverse perinatal outcome was defined as stillbirth, neonatal death, or neonatal morbidity, the latter identified using the English composite neonatal outcome indicator (E-NAOI). Binomial regression models estimated risk differences (with 95% confidence intervals (CIs)) between the IOL group and the expectant management group, adjusting for ethnicity, socioeconomic background, maternal age, parity, year of birth, and birthweight centile. Interaction tests examined risk differences according to ethnicity, socioeconomic background, and parity. Of the 1 567 004 women with singleton pregnancies, 501 072 women with low-risk pregnancies and with sufficient data quality were included in the analysis. Approximately 3.3% of births in the IOL group (1 555/47 352) and 3.6% in the expectant management group (16 525/453 720) had an adverse perinatal outcome. After adjustment, a lower risk of adverse perinatal outcomes was found in the IOL group (risk difference -0.28%; 95% CI -0.43%, -0.12%; p = 0.001). This risk difference varied according to socioeconomic background from 0.38% (-0.08%, 0.83%) in the least deprived to -0.48% (-0.76%, -0.20%) in the most deprived national quintile (p-value for interaction = 0.01) and by parity with risk difference of -0.54% (-0.80%, -0.27%) in nulliparous women and -0.15% (-0.35%, 0.04%) in multiparous women (p-value for interaction = 0.02). There was no statistically significant evidence that risk differences varied according to ethnicity (p = 0.19). Key limitations included absence of additional confounding factors such as smoking, BMI, and the indication for induction in the HES datasets, which may mean some higher risk pregnancies were included.

CONCLUSIONS

IOL with birth at 39 weeks was associated with a small reduction in the risk of adverse perinatal outcomes, with 360 inductions in low-risk pregnancies needed to avoid 1 adverse outcome. The risk reduction was mainly present in women from more socioeconomically deprived areas and in nulliparous women. There was no significant risk difference found by ethnicity. Increased uptake of IOL at 39 weeks, especially in women from more socioeconomically deprived areas, may help reduce inequalities in adverse perinatal outcomes.

The infant health effects of starting universal child benefits in pregnancy: Evidence from England and Wales

Child benefits are typically paid from birth. This paper asks whether starting universal child benefits in pregnancy leads to improvements in infant health. Leveraging administrative birth registry and hospital microdata from England and Wales, I study the effects of the Health in Pregnancy Grant, a universal conditional cash transfer equivalent to three months of child benefit (190 GBP) as a lump sum to pregnant mothers from 2009 to 2011. I exploit quasi-experimental variation in eligibility with a regression discontinuity design in the date of birth of the baby. I find that the policy increased birth weight by 8-12 grams on average, reduced low birth weight (<2500 g) by 3-6 percent and decreased prematurity by 9-11 percent. Younger mothers, particularly those living in deprived areas, benefit the most. I present evidence that the mechanisms are unlikely to be antenatal care, nutrition or smoking, with reductions in stress remaining a possible explanation.

Linkage of maternity hospital episode statistics birth records to birth registration and notification records for births in England 2005-2006: quality assurance of linkage

OBJECTIVES

The objectives of this study were to describe the methods used to assess the quality of linkage between records of babies' birth registration and hospital birth records, and to evaluate the potential bias that may be introduced because of these methods.

DESIGN/SETTING

Data from the civil registration and the notification of births previously linked by the Office for National Statistics (ONS) had been further linked to birth records from the Hospital Episode Statistics (HES) for babies born in England. We developed a deterministic, six-stage algorithm to assess the quality of this linkage.

PARTICIPANTS

All 1 170 790 live, singleton births, occurring in National Health Service hospitals in England between 1 January 2005 and 31 December 2006.

PRIMARY OUTCOME MEASURE

The primary outcome was the number of successful links between ONS birth records and HES birth records. Rates of successful linkage were calculated for the cohort and the characteristics associated with unsuccessful linkage were identified.

RESULTS

Approximately 92% (1 074 572) of the birth registration records were successfully linked with a HES birth record. Data quality and completeness were somewhat poorer in HES birth records compared with linked birth registration and birth notification records. The quality assurance algorithms identified 1456 incorrect linkages (<1%). Compared with the linked dataset, birth records were more likely to be unlinked if babies were of white ethnic origin; born to unmarried mothers; born in East England, London, North West England or the West Midlands; or born in March.

CONCLUSIONS

It is possible to link administrative datasets to create large cohorts, allowing researchers to explore important questions about exposures and childhood outcomes. Missing data, coding errors and inconsistencies mean it is important that the quality of linkage is assessed prior to analysis.

Ten-year follow-up of a randomised trial of drainage, irrigation and fibrinolytic therapy (DRIFT) in infants with post-haemorrhagic ventricular dilatation

BACKGROUND

The drainage, irrigation and fibrinolytic therapy (DRIFT) trial, conducted in 2003-6, showed a reduced rate of death or severe disability at 2 years in the DRIFT compared with the standard treatment group, among preterm infants with intraventricular haemorrhage (IVH) and post-haemorrhagic ventricular dilatation.

OBJECTIVES

To compare cognitive function, visual and sensorimotor ability, emotional well-being, use of specialist health/rehabilitative and educational services, neuroimaging, and economic costs and benefits at school age.

DESIGN

Ten-year follow-up of a randomised controlled trial.

SETTING

Neonatal intensive care units (Bristol, Katowice, Glasgow and Bergen).

PARTICIPANTS

Fifty-two of the original 77 infants randomised.

INTERVENTIONS

DRIFT or standard therapy (cerebrospinal fluid tapping).

MAIN OUTCOME MEASURES

Primary - cognitive disability. Secondary - vision; sensorimotor disability; emotional/behavioural function; education; neurosurgical sequelae on magnetic resonance imaging; preference-based measures of health-related quality of life; costs of neonatal treatment and of subsequent health care in childhood; health and social care costs and impact on family at age 10 years; and a decision analysis model to estimate the cost-effectiveness of DRIFT compared with standard treatment up to the age of 18 years.

RESULTS

By 10 years of age, 12 children had died and 13 were either lost to follow-up or had declined to participate. A total of 52 children were assessed at 10 years of age (DRIFT, n = 28; standard treatment, n = 24). Imbalances in gender and birthweight favoured the standard treatment group. The unadjusted mean cognitive quotient (CQ) score was 69.3 points [standard deviation (SD) 30.1 points] in the DRIFT group compared with 53.7 points (SD 35.7 points) in the standard treatment group, a difference of 15.7 points, 95% confidence interval (CI) -2.9 to 34.2 points; p = 0.096. After adjusting for the prespecified covariates (gender, birthweight and grade of IVH), this evidence strengthened: children who received DRIFT had a CQ advantage of 23.5 points (p = 0.009). The binary outcome, alive without severe cognitive disability, gave strong evidence that DRIFT improved cognition [unadjusted odds ratio (OR) 3.6 (95% CI 1.2 to 11.0; p = 0.026) and adjusted OR 10.0 (95% CI 2.1 to 46.7; p = 0.004)]; the number needed to treat was three. No significant differences were found in any secondary outcomes. There was weak evidence that DRIFT reduced special school attendance (adjusted OR 0.27, 95% CI 0.07 to 1.05; p = 0.059). The neonatal stay (unadjusted mean difference £6556, 95% CI -£11,161 to £24,273) and subsequent hospital care (£3413, 95% CI -£12,408 to £19,234) costs were higher in the DRIFT arm, but the wide CIs included zero. The decision analysis model indicated that DRIFT has the potential to be cost-effective at 18 years of age. The incremental cost-effectiveness ratio (£15,621 per quality-adjusted life-year) was below the National Institute for Health and Care Excellence threshold. The cost-effectiveness results were sensitive to adjustment for birthweight and gender.

LIMITATIONS

The main limitations are the sample size of the trial and that important characteristics were unbalanced at baseline and at the 10-year follow-up. Although the analyses conducted here were prespecified in the analysis plan, they had not been prespecified in the original trial registration.

CONCLUSIONS

DRIFT improves cognitive function when taking into account birthweight, grade of IVH and gender. DRIFT is probably effective and, given the reduction in the need for special education, has the potential to be cost-effective as well. A future UK multicentre trial is required to assess efficacy and safety of DRIFT when delivered across multiple sites.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN80286058.

FUNDING

This project was funded by the NIHR Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 23, No. 4. See the NIHR Journals Library website for further project information. The DRIFT trial and 2-year follow-up was funded by Cerebra and the James and Grace Anderson Trust.

Small-area methods for investigation of environment and health

Small-area studies offer a powerful epidemiological approach to study disease patterns at the population level and assess health risks posed by environmental pollutants. They involve a public health investigation on a geographical scale (e.g. neighbourhood) with overlay of health, environmental, demographic and potential confounder data. Recent methodological advances, including Bayesian approaches, combined with fast-growing computational capabilities, permit more informative analyses than previously possible, including the incorporation of data at different scales, from satellites to individual-level survey information. Better data availability has widened the scope and utility of small-area studies, but has also led to greater complexity, including choice of optimal study area size and extent, duration of study periods, range of covariates and confounders to be considered and dealing with uncertainty. The availability of data from large, well-phenotyped cohorts such as UK Biobank enables the use of mixed-level study designs and the triangulation of evidence on environmental risks from small-area and individual-level studies, therefore improving causal inference, including use of linked biomarker and -omics data. As a result, there are now improved opportunities to investigate the impacts of environmental risk factors on human health, particularly for the surveillance and prevention of non-communicable diseases.

Ethnic differences in singleton preterm birth in England and Wales, 2006-12: Analysis of national routinely collected data

BACKGROUND

Data recorded at birth and death registration in England and Wales have been routinely linked with data recorded at birth notification since 2006. These provide scope for detailed analyses on ethnic differences in preterm birth (PTB).

OBJECTIVES

We aimed to investigate ethnic differences in PTB and degree of prematurity in England and Wales, taking into account maternal sociodemographic characteristics and to further explore the contribution of mother's country of birth to these ethnic differences in PTB.

METHODS

We analysed PTB and degree of prematurity by ethnic group, using routinely collected and linked data for all singleton live births in England and Wales, 2006-2012. Logistic regression was used to adjust for mother's age, marital status/registration type, area deprivation and mother's country of birth.

RESULTS

In the 4 634 932 births analysed, all minority ethnic groups except 'Other White' had significantly higher odds of PTB compared with White British babies (ORs between 1.04-1.25); highest odds were in Black Caribbean, Indian, Bangladeshi and Pakistani groups. Ethnic differences in PTB tended to be greater at earlier gestational ages. In all ethnic groups, odds of PTB were lower for babies whose mothers were born outside the UK.

CONCLUSIONS

In England and Wales, Black Caribbean, Indian, Bangladeshi, Pakistani and Black African babies all have significantly increased odds of being born preterm compared with White British babies. Bangladeshis apart, these groups are particularly at risk of extremely PTB. In all ethnic groups, the odds of PTB are lower for babies whose mothers were born outside the UK. These ethnic differences do not appear to be wholly explained by area deprivation or other sociodemographic characteristics.

Births and their outcomes by time, day and year: a retrospective birth cohort data linkage study

Background

Studies of daily variations in the numbers of births in England and Wales since the 1970s have found a pronounced weekly cycle, with numbers of daily births being highest from Tuesdays to Fridays and lowest at weekends and on public holidays. Mortality appeared to be higher at weekends. As time of birth was not included in national data systems until 2005, there have been no previous analyses by time of day.

Objectives

To link data from birth registration and birth notification to data about care during birth and any subsequent hospital admissions and to quality assure the linkage. To use the linked data to analyse births and their outcomes by time of day, day of the week and year of birth.

Design

A retrospective birth cohort analysis of linked routine data.

Setting

England and Wales.

Outcome measures

Mortality of babies and mothers, and morbidity recorded at birth and any subsequent hospital admission.

Population and data sources

Birth registration and notification records of 7,013,804 births in 2005–14, already linked to subsequent death registration records for babies, children and women who died within 1 year of giving birth, were provided by the Office for National Statistics. Stillbirths and neonatal deaths data from confidential enquiries for 2005–9 were linked to the registration records. Data for England were linked to Hospital Episode Statistics (HES) and data for Wales were linked to the Patient Episode Database for Wales and the National Community Child Health Database.

Results

Cross-sectional analysis of all births in England and Wales showed a regular weekly cycle. Numbers of births each day increased from Mondays to Fridays. Numbers were lowest at weekends and on public holidays. Overall, numbers of births peaked between 09.00 and 12.00, followed by a much smaller peak in the early afternoon and a decrease after 17.00. Numbers then increased from 20.00, peaking at around 03.00–05.00, before falling again after 06.00. Singleton births after spontaneous onset and birth, including births in freestanding midwifery units and at home, were most likely to occur between midnight and 06.00, peaking at 04.00–06.00. Elective caesarean births were concentrated in weekday mornings. Births after induced labours were more likely to occur at hours around midnight on Tuesdays to Saturdays, irrespective of the mode of birth.

Limitations

The project was delayed by data access and information technology infrastructure problems. Data from confidential enquiries were available only for 2005–9 and some HES variables were incomplete. There was insufficient time to analyse the mortality and morbidity outcomes.

Conclusions

The timing of birth varies by place of birth, onset of labour and mode of birth. These patterns have implications for midwifery and medical staffing.

Future work

An application has now been submitted for funding to analyse the mortality outcomes and further funding will be sought to undertake the other outstanding analyses.

Funding

This project was funded by the National Institute for Health Research (NIHR) Health Services and Delivery Research programme and will be published in full inHealth Services and Delivery Research; Vol. 7, No. 18. See the NIHR Journals Library website for further project information.

Timing of singleton births by onset of labour and mode of birth in NHS maternity units in England, 2005-2014: A study of linked birth registration, birth notification, and hospital episode data

BACKGROUND

Maternity care has to be available 24 hours a day, seven days a week. It is known that obstetric intervention can influence the time of birth, but no previous analysis at a national level in England has yet investigated in detail the ways in which the day and time of birth varies by onset of labour and mode of giving birth.

METHOD

We linked data from birth registration, birth notification, and Maternity Hospital Episode Statistics and analysed 5,093,615 singleton births in NHS maternity units in England from 2005 to 2014. We used descriptive statistics and negative binomial regression models with harmonic terms to establish how patterns of timing of birth vary by onset of labour, mode of giving birth and gestational age.

RESULTS

The timing of birth by time of day and day of the week varies considerably by onset of labour and mode of birth. Spontaneous births after spontaneous onset are more likely to occur between midnight and 6am than at other times of day, and are also slightly more likely on weekdays than at weekends and on public holidays. Elective caesarean births are concentrated onto weekday mornings. Births after induced labours are more likely to occur at hours around midnight on Tuesdays to Saturdays and on days before a public holiday period, than on Sundays, Mondays and during or just after a public holiday.

CONCLUSION

The timing of births varies by onset of labour and mode of birth and these patterns have implications for midwifery and medical staffing. Further research is needed to understand the processes behind these findings.

Birth weight trends in England and Wales (1986-2012): babies are getting heavier

INTRODUCTION

Birth weight is a strong predictor of infant mortality, morbidity and later disease risk. Previous work from the 1980s indicated a shift in the UK towards heavier births; this descriptive analysis looks at more recent trends.

METHODS

Office for National Statistics (ONS) registration data on 17.2 million live, single births from 1986 to 2012 were investigated for temporal trends in mean birth weight, potential years of birth weight change and changes in the proportions of very low (<1500 g), low (<2500 g) and high (≥4000 g) birth weight. Analysis used multiple linear and logistic regression adjusted for maternal age, marital status, area-level deprivation and ethnicity. Additional analyses used the ONS NHS Numbers for Babies data set for 2006-2012, which has information on individual ethnicity and gestational age.

RESULTS

Over 27 years there was an increase in birth weight of 43 g (95% CI 42 to 44) in females and 44 g (95% CI 43 to 45) in males, driven by birth weight increases between 1986-1990 and 2007-2012. There was a concurrent decreased risk of having low birth weight but an 8% increased risk in males and 10% increased risk in females of having high birth weight. For 2006-2012 the birth weight increase was greater in preterm as compared with term births.

CONCLUSIONS

Since 1986 the birth weight distribution of live, single births in England and Wales has shifted towards heavier births, partly explained by increases in maternal age and non-white ethnicity, as well as changes in deprivation levels. Other potential influences include increases in maternal obesity and reductions in smoking prevalence particularly following the introduction of legislation restricting smoking in public places in 2007.

Linkage of Maternity Hospital Episode Statistics data to birth registration and notification records for births in England 2005-2014: Quality assurance of linkage of routine data for singleton and multiple births

OBJECTIVES

To quality assure a Trusted Third Party linked data set to prepare it for analysis.

SETTING

Birth registration and notification records from the Office for National Statistics for all births in England 2005-2014 linked to Maternity Hospital Episode Statistics (HES) delivery records by NHS Digital using mothers' identifiers.

PARTICIPANTS

All 6 676 912 births that occurred in England from 1 January 2005 to 31 December 2014.

PRIMARY AND SECONDARY OUTCOME MEASURES

Every link between a registered birth and an HES delivery record for the study period was categorised as either the same baby or a different baby to the same mother, or as a wrong link, by comparing common baby data items and valid values in key fields with stepwise deterministic rules. Rates of preserved and discarded links were calculated and which features were more common in each group were assessed.

RESULTS

Ninety-eight per cent of births originally linked to HES were left with one preserved link. The majority of discarded links were due to duplicate HES delivery records. Of the 4854 discarded links categorised as wrong links, clerical checks found 85% were false-positives links, 13% were quality assurance false negatives and 2% were undeterminable. Births linked using a less reliable stage of the linkage algorithm, births at home and in the London region, and with birth weight or gestational age values missing in HES were more likely to have all links discarded.

CONCLUSIONS

Linkage error, data quality issues, and false negatives in the quality assurance procedure were uncovered. The procedure could be improved by allowing for transposition in date fields, and more discrimination between missing and differing values. The availability of identifiers in the datasets supported clerical checking. Other research using Trusted Third Party linkage should not assume the linked dataset is error-free or optimised for their analysis, and allow sufficient resources for this.

Linkage of Maternity Hospital Episode Statistics data to birth registration and notification records for births in England 2005-2014: methods. A population-based birth cohort study

INTRODUCTION

Maternity Hospital Episode Statistics (HES) data for 2005-2014 were linked to birth registration and birth notification data (previously known as NHS Numbers for Babies or NN4B) to bring together some key demographic and clinical data items not otherwise available at a national level. The linkage algorithm that was previously used to link 2005-2007 data was revised to improve the linkage rate and reduce the number of duplicate HES records.

METHODS

Birth registration and notification linked records from the Office for National Statistics ('ONS birth records') were further linked to Maternity HES delivery and birth records using the NHS Number and other direct identifiers if the NHS Number was missing.

RESULTS

For the period 2005-2014, over 94% of birth registration and notification records were correctly linked to HES delivery records. Two per cent of the ONS birth records were incorrectly linked to the HES delivery record and 5% of ONS birth records were linked to more than one HES delivery record. Therefore, a considerable amount of time was spent in quality assuring these files.

CONCLUSION

The linkage rate for birth registration and notification records to HES delivery records steadily improved from 2005 to 2014 due to improvement in the quality and completeness of patient identifiers in both HES and birth notification data.

Perinatal mortality associated with induction of labour versus expectant management in nulliparous women aged 35 years or over: An English national cohort study

BACKGROUND

A recent randomised controlled trial (RCT) demonstrated that induction of labour at 39 weeks of gestational age has no short-term adverse effect on the mother or infant among nulliparous women aged ≥35 years. However, the trial was underpowered to address the effect of routine induction of labour on the risk of perinatal death. We aimed to determine the association between induction of labour at ≥39 weeks and the risk of perinatal mortality among nulliparous women aged ≥35 years.

METHODS AND FINDINGS

We used English Hospital Episode Statistics (HES) data collected between April 2009 and March 2014 to compare perinatal mortality between induction of labour at 39, 40, and 41 weeks of gestation and expectant management (continuation of pregnancy to either spontaneous labour, induction of labour, or caesarean section at a later gestation). Analysis was by multivariable Poisson regression with adjustment for maternal characteristics and pregnancy-related conditions. Among the cohort of 77,327 nulliparous women aged 35 to 50 years delivering a singleton infant, 33.1% had labour induced: these women tended to be older and more likely to have medical complications of pregnancy, and the infants were more likely to be small for gestational age. Induction of labour at 40 weeks (compared with expectant management) was associated with a lower risk of in-hospital perinatal death (0.08% versus 0.26%; adjusted risk ratio [adjRR] 0.33; 95% CI 0.13-0.80, P = 0.015) and meconium aspiration syndrome (0.44% versus 0.86%; adjRR 0.52; 95% CI 0.35-0.78, P = 0.002). Induction at 40 weeks was also associated with a slightly increased risk of instrumental vaginal delivery (adjRR 1.06; 95% CI 1.01-1.11, P = 0.020) and emergency caesarean section (adjRR 1.05; 95% CI 1.01-1.09, P = 0.019). The number needed to treat (NNT) analysis indicated that 562 (95% CI 366-1,210) inductions of labour at 40 weeks would be required to prevent 1 perinatal death. Limitations of the study include the reliance on observational data in which gestational age is recorded in weeks rather than days. There is also the potential for unmeasured confounders and under-recording of induction of labour or perinatal death in the dataset.

CONCLUSIONS

Bringing forward the routine offer of induction of labour from the current recommendation of 41-42 weeks to 40 weeks of gestation in nulliparous women aged ≥35 years may reduce overall rates of perinatal death.

Explaining ethnic disparities in lung function among young adults: A pilot investigation

Background

Ethnic disparities in lung function have been linked mainly to anthropometric factors but have not been fully explained. We conducted a cross-sectional pilot study to investigate how best to study ethnic differences in lung function in young adults and evaluate whether these could be explained by birth weight and socio-economic factors.

Methods

We recruited 112 university students of White and South Asian British ethnicity, measured post-bronchodilator lung function, obtained information on respiratory symptoms and socio-economic factors through questionnaires, and acquired birth weight through data linkage. We regressed lung function against ethnicity and candidate predictors defined a priori using linear regression, and used penalised regression to examine a wider range of factors. We reviewed the implications of our findings for the feasibility of a larger study.

Results

There was a similar parental socio-economic environment and no difference in birth weight between the two ethnic groups, but the ethnic difference in FVC adjusted for sex, age, height, demi-span, father’s occupation, birth weight, maternal educational attainment and maternal upbringing was 0.81L (95%CI: -1.01 to -0.54L). Difference in body proportions did not explain the ethnic differences although parental immigration was an important predictor of FVC independent of ethnic group. Participants were comfortable with study procedures and we were able to link birth weight data to clinical measurements.

Conclusion

Studies of ethnic disparities in lung function among young adults are feasible. Future studies should recruit a socially more diverse sample and investigate the role of markers of acculturation in explaining such differences.

Pregnancy and Labor Complications in Female Survivors of Childhood Cancer: The British Childhood Cancer Survivor Study

Background: Female survivors of childhood cancer treated with abdominal radiotherapy who manage to conceive are at risk of delivering premature and low-birthweight offspring, but little is known about whether abdominal radiotherapy may also be associated with additional complications during pregnancy and labor. We investigated the risk of developing pregnancy and labor complications among female survivors of childhood cancer in the British Childhood Cancer Survivor Study (BCCSS).

Methods: Pregnancy and labor complications were identified by linking the BCCSS cohort (n = 17 980) to the Hospital Episode Statistics (HES) for England. Relative risks (RRs) of pregnancy and labor complications were calculated by site of radiotherapy treatment (none/abdominal/cranial/other) and other cancer-related factors using log-binomial regression. All statistical tests were two-sided.

Results: A total of 2783 singleton pregnancies among 1712 female survivors of childhood cancer were identified in HES. Wilms tumor survivors treated with abdominal radiotherapy were at threefold risk of hypertension complicating pregnancy (relative risk = 3.29, 95% confidence interval [CI] = 2.29 to 4.71), while all survivors treated with abdominal radiotherapy were at risk of gestational diabetes mellitus (RR = 3.35, 95% CI = 1.41 to 7.93) and anemia complicating pregnancy (RR = 2.10, 95% CI = 1.27 to 3.46) compared with survivors treated without radiotherapy. Survivors treated without radiotherapy had similar risks of pregnancy and labor complications as the general population, except survivors were more likely to opt for an elective cesarean section (RR = 1.39, 95% CI = 1.16 to 1.70).

Conclusions: Treatment with abdominal radiotherapy increases the risk of developing hypertension complicating pregnancy in Wilms tumor survivors, and diabetes mellitus and anemia complicating pregnancy in all survivors. These patients may require extra vigilance during pregnancy.