The fetuses-at-risk approach: survival analysis from a fetal perspective

Stillbirth risk by fetal size among 126.5 million births in 15 countries from 2000 to 2020: A fetuses-at-risk approach

OBJECTIVE

To compare stillbirth rates and risks for small for gestational age (SGA), large for gestational age (LGA) and appropriate for gestational age (AGA) pregnancies at 24-44 completed weeks of gestation using a birth-based and fetuses-at-risk approachs.

DESIGN

Population-based, multi-country study.

SETTING

National data systems in 15 high- and middle-income countries.

POPULATION

Live births and stillbirths.

METHODS

A total of 151 country-years of data, including 126 543 070 births across 15 countries from 2000 to 2020, were compiled. Births were categorised into SGA, AGA and LGA using INTERGROWTH-21st standards. Gestation-specific stillbirth rates, with total births as the denominator, and gestation-specific stillbirth risks, with fetuses still in utero as the denominator, were calculated from 24 to 44 weeks of gestation.

MAIN OUTCOME MEASURES

Gestation-specific stillbirth rates and risks according to size at birth.

RESULTS

The overall stillbirth rate was 4.22 per 1000 total births (95% CI 4.22-4.23) across all gestations. Applying the birth-based approach, the stillbirth rates were highest at 24 weeks of gestation, with 621.6 per 1000 total births (95% CI 620.9-622.2) for SGA pregnancies, 298.4 per 1000 total births (95% CI 298.1-298.7) for AGA pregnancies and 338.5 per 1000 total births (95% CI 337.9-339.0) for LGA pregnancies. Applying the fetuses-at-risk approach, the gestation-specific stillbirth risk was highest for SGA pregnancies (1.3-1.4 per 1000 fetuses at risk) prior to 29 weeks of gestation. The risk remained stable between 30 and 34 weeks of gestation, and then increased gradually from 35 weeks of gestation to the highest rate of 8.4 per 1000 fetuses at risk (95% CI 8.3-8.4) at ≥42 weeks of gestation. The stillbirth risk ratio (RR) was consistently high for SGA compared with AGA pregnancies, with the highest RR observed at ≥42 weeks of gestation (RR 9.2, 95% CI 15.2-13.2), and with the lowest RR observed at 24 weeks of gestation (RR 3.1, 95% CI 1.9-4.3). The stillbirth RR was also consistently high for SGA compared with AGA pregnancies across all countries, with national variability ranging from RR 0.70 (95% CI 0.43-0.97) in Mexico to RR 8.6 (95% CI 8.1-9.1) in Uruguay. No increased risk for LGA pregnancies was observed.

CONCLUSIONS

Small for gestational age (SGA) was strongly associated with stillbirth risk in this study based on high-quality data from high- and middle-income countries. The highest RRs were seen in preterm gestations, with two-thirds of the stillbirths born as preterm births. To advance our understanding of stillbirth, further analyses should be conducted using high-quality data sets from low-income settings, particularly those with relatively high rates of SGA.

Prevalence and risk of stillbirth according to biologic vulnerability phenotypes in the municipality of São Paulo, Brazil: A population-based cohort study

OBJECTIVE

To estimate the prevalence and risk of stillbirths by biologic vulnerability phenotypes in a cohort of pregnant women in the municipality of São Paulo, Brazil, 2017-2019.

METHODS

Retrospective population-based cohort study. Fetuses were assessed as small for gestational age (SGA), large for gestational age (LGA), adequate for gestational age (AGA), preterm (PT) as less than 37 weeks of gestation, non-PT (NPT) as 37 weeks of gestation or more, low birth weight (LBW) as less than 2500 g, and non-LBW (NLBW) as 2500 g or more. Relative risks (RR) with robust variance were estimated using Poisson regression.

RESULTS

In all 442 782 pregnancies, including 2321 (0.5%) stillbirths, were included. About 85% (n = 1983) of stillbirths had at least one characteristic of vulnerability, compared with 21% (n = 92524) of live births. Fetuses with all three markers of vulnerability had the highest adjusted RR of stillbirth-SGA + LBW + PT (RR 155.00; 95% confidence interval [CI] 136.29-176.30) and LGA + LBW + PT (RR 262.04; 95% CI 206.10-333.16) when compared with AGA + NLBW + NPT.

CONCLUSION

Our findings show that the simultaneous presence of prematurity, low birth weight, and abnormal intrauterine growth presented a higher risk of stillbirths. To accelerate progress towards reducing preventable stillbirths, one must identify the circumstances of greatest biologic vulnerability.

Missing Black males among preterm births in the US, 1995 to 2019

BACKGROUND

In the US, non-Hispanic (NH) Black birthing persons show a two-fold greater risk of fetal death relative to NH white birthing persons. Since males more than females show a greater risk of fetal death, such loss in utero may affect the sex composition of live births born preterm (PTB; <37 weeks gestational age). We examine US birth data from 1995 to 2019 to determine whether the ratio of male to female preterm (i.e., PTB sex ratios) among NH Black births falls below that of NH whites and Hispanics.

METHODS

We acquired data on all live births in the US from January 1995 to December 2019. We arrayed 63 million live births into 293 "conception cohort" months of which 2,475,928 NH Black, 5,746,953 NH white, and 2,511,450 Hispanic infants were PTB. We used linear regression methods to identify trend and seasonal patterns in PTB sex ratios. We also examined subgroup differences in PTB sex ratios (e.g., advanced maternal ages, twin gestations, and narrower gestational age ranges).

RESULTS

The mean PTB sex ratio for NH Black births over the entire test period (1.06, 95% Confidence Interval [CI]: 1.05, 1.07) is much lower than that for NH white births (1.18, 95% CI: 1.17, 1.19). NH Black PTB sex ratios are especially low for twins and for births to mothers 35 years or older. Only NH white PTB sex ratios show a trend over the test period.

CONCLUSIONS

Analysis of over 10 million PTBs reveals a persistently low male PTB frequency among NH Black conception cohorts relative to NH white cohorts. Low PTB sex ratios among NH Black births concentrate among subgroups that show an elevated risk of fetal death. PTB sex ratios may serve as an indicator of racial/ethnic and subgroup differences in fetal death, especially among male gestations.

The impact of isolated obesity compared with obesity and other risk factors on risk of stillbirth: a retrospective cohort study

BACKGROUND

Maternal obesity is associated with stillbirth, but uncertainty persists around the effects of higher obesity classes. We sought to compare the risk of stillbirth associated with maternal obesity alone versus maternal obesity and additional or undiagnosed factors contributing to high-risk pregnancy.

METHODS

We conducted a retrospective cohort study using the Better Outcomes Registry and Network (BORN) for singleton hospital births in Ontario between 2012 and 2018. We used multivariable Cox proportional hazard regression and logistic regression to evaluate the relationship between prepregnancy maternal body mass index (BMI) class and stillbirth (reference was normal BMI). We treated maternal characteristics and obstetrical complications as independent covariates. We performed mediator analyses to measure the direct and indirect effects of BMI on stillbirth through major common-pathway complications. We used fully adjusted and partially adjusted models, representing the impact of maternal obesity alone and maternal obesity with other risk factors on stillbirth, respectively.

RESULTS

We analyzed data on 681 178 births between 2012 and 2018, of which 1956 were stillbirths. Class I obesity was associated with an increased incidence of stillbirth (adjusted hazard ratio [HR] 1.55, 95% confidence interval [CI] 1.35-1.78). This association was stronger for class III obesity (adjusted HR 1.80, 95% CI 1.44-2.24), and strongest for class II obesity (adjusted HR 2.17, 95% CI 1.83-2.57). Plotting point estimates for odds ratios, stratified by gestational age, showed a marked increase in the relative odds for stillbirth beyond 37 weeks' gestation for those with obesity with and without other risk factors, compared with those with normal BMI. The impact of potential mediators was minimal.

INTERPRETATION

Maternal obesity alone and obesity with other risk factors are associated with an increased risk of stillbirth. This risk increases with gestational age, especially at term.

Indications affect neonatal outcomes following early rescue ICSI: a retrospective study

PURPOSE

To investigate the impact of heterogeneity in patient indications or insemination protocols on neonatal outcomes of singletons following early rescue ICSI (rICSI) treatments.

METHODS

A retrospective study was conducted. Propensity score matching and multivariable logistic regression were used to adjust for confounders and biases.

RESULTS

A total of 9095 IVF patients, 2063 ICSI patients, and 642 early rICSI patients were included in the study. No differences were detected in neonatal outcomes except small for gestational age (SGA) which increased in early rICSI patients compared with both unmatched and matched IVF groups with the risk ratio (RR) of 1.31 (95% CI: 1.05, 1.64) and 1.49 (95% CI: 1.05, 2.12). Further analysis showed that SGA increased significantly in partial fertilization failure (PFF) cycles with RRs of 1.56 (95% CI: 1.08, 2.27) and 1.78 (95% CI: 1.22, 2.59) compared with both unmatched and matched IVF patients but not in TFF patients. A positive association between fertilization rate via IVF and birth weight z-score was revealed in the PFF patients.

CONCLUSION

Early rICSI in patients with total fertilization failure (TFF) appeared to be safe in terms of neonatal outcomes. However, when expanding the indications of rICSI to PFF patients, the SGA in the offspring increased, suggesting a potential effect on long-term health. Since other treatment options, such as using only the IVF-origin embryos still exist for these patients, further studies were needed to confirm the optimal decision for these patients.

Cohort selection and the estimation of racial disparity in mortality of extremely preterm neonates

BACKGROUND

Racial disparities in preterm neonatal mortality are long-standing. We aimed to assess how cohort selection influences mortality rates and racial disparity estimates.

METHODS

With 2014-2018 California data, we compared neonatal mortality rates among Black and non-Hispanic White very low birth weight (VLBW, <1500 g) or very preterm infants (22-29 weeks gestational age). Relative risks were estimated by different cohort selection criteria. Blinder-Oaxaca decomposition quantified factors contributing to mortality differential.

RESULTS

Depending upon standard selection criteria, mortality ranged from 6.2% (VLBW infants excluding first 12-h deaths) to 16.0% (22-29 weeks' gestation including all deaths). Black observed neonatal mortality was higher than White infants only for delivery room deaths in VLBW infants (5.6 vs 4.2%). With risk adjustment accounting for higher rate of low gestational age, low Apgar score and other factors, White infant mortality increased from 15.9 to 16.6%, while Black infant mortality decreased from 16.7 to 13.7% in the 22-29 weeks cohort. Across varying cohort selection, risk adjusted survival advantage among Black infants ranged from 0.70 (CL 0.61-0.80) to 0.84 (CL 0.76-0.93).

CONCLUSIONS

Standard cohort selection can give markedly different mortality estimates. It is necessary to reduce prematurity rates and perinatal morbidity to improve outcomes for Black infants.

IMPACT

In this population-based observational cohort study that encompassed very low birth weight infant hospitalizations in California, varying standard methods of cohort selection resulted in neonatal mortality ranges from 6.2 to 16.0%. Across all cohorts, the only significant observed Black-White disparity was for delivery room deaths in Very Low Birth Weight births (5.6 vs 4.2%). Across all cohorts, we found a 16-30% survival advantage for Black infants. Cohort selection can result in an almost three-fold difference in estimated mortality but did not have a meaningful impact on observed or adjusted differences in neonatal mortality outcomes by race and ethnicity.

Sex differences in growth and mortality in pregnancy-associated hypertension

BACKGROUND

It is hypothesized that male fetuses prioritize growth, resulting in increased mortality, whereas females reduce growth in the presence of adversity. Preeclampsia reflects a chronic condition, in which fetuses have the opportunity to adjust growth. If females reduce their growth in response to preeclampsia, but males attempt to maintain growth at the cost of survival, we predict that differences in birthweight between preeclamptic and non-preeclamptic pregnancies will be greater among females, whereas differences in mortality will be greater among males.

METHODS

We analysed data from the Centers for Disease Control and Prevention. We compared pregnancies with pregnancy-associated hypertension (PAH) and controls.

RESULTS

The difference in birthweight between pregnancies affected by PAH and controls varied by fetal sex and gestational age. Among pregnancies of White individuals, at 34-35 weeks, the difference between PAH and controls was higher among females, as predicted. However, this pattern was reversed earlier in pregnancy and around term. Such variation was not significant in Black pregnancies. In both Black and White pregnancies, early in gestation, males had lower odds of death in PAH pregnancies, but higher odds of death in control pregnancies, counter to our prediction. Later, males had higher odds of death in PAH and controls, although the increased odds of death in males was not higher in PAH pregnancies than in controls. Overall, the difference in birthweight between surviving and non-surviving infants was greater in males than in females, opposite to our prediction.

CONCLUSIONS

The impact of PAH on birthweight and survival varies widely throughout gestation. Differences in birthweight and survival between male and female PAH and controls are generally not consistent with the hypothesis that males prioritize fetal growth more than females, and that this is a cause of increased mortality in males.

Neonatal and Early Childhood Outcomes of Twin and Singleton Infants Born Preterm

OBJECTIVE

To compare neonatal and early-childhood outcomes of twins and singletons born preterm and explore the association of chorionicity with outcomes.

STUDY DESIGN

This was a national retrospective cohort study of singleton and twin infants admitted at 230/7-286/7 weeks to level III neonatal intensive care units in Canada (2010-2020). The primary neonatal outcome was a composite of neonatal death or severe neonatal morbidities. The primary early-childhood outcome was a composite of death or significant neurodevelopmental impairment.

RESULTS

The study cohort included 3554 twin and 12 815 singleton infants. Twin infants born at 230/7-256/7 weeks had a greater risk of the composite neonatal outcome (adjusted risk ratio 1.04, 95% CI 1.01-1.07). However, these differences were limited to the subgroups of same-sex and monochorionic twin pregnancies. Twin infants of 230/7-256/7 weeks were also at an increased risk of the composite early-childhood outcome (adjusted risk ratio 1.22, 95% CI 1.09-1.37). Twin infants of 260/7-286/7 weeks were not at an increased risk of adverse neonatal outcomes or the composite early-childhood outcome compared with singleton infants.

CONCLUSIONS

Among infants born at 230/7-256/7 weeks, twins have a greater risk of adverse neonatal outcomes and the composite early-childhood outcome than singleton infants. However, the increased risk of adverse neonatal outcomes is mostly limited to monochorionic twins and may thus be driven by complications related to monochorionic placentation.

A flexible approach to modelling stillbirths using the foetuses at risk approach

BACKGROUND

Survival analysis methods are increasingly used to model the gestational age-specific risk of perinatal phenomena such as stillbirth.

OBJECTIVES

To compare two types of survival analysis models, and highlight differences by estimating the relationships between pre-pregnancy BMI and gestational age-specific rates of stillbirth.

METHODS

The study was based on singleton live births and stillbirths in the United States in 2016-2017, with data obtained from the natality and fetal death files of the National Center for Health Statistics. We compared Cox regression versus piecewise exponential additive mixed models (PAMMs) for modelling the relationship between BMI and stillbirth across gestational age. In a second analysis, we illustrated the performance of both models for assessing the relationship between the trimester-specific number of cigarettes smoked, a time-dependent covariate, and stillbirth.

RESULTS

The study population included 7,567,316 births, of which 42,739 were stillbirths (5.6 per 1000 total births). Stillbirth rates increased with increasing pre-pregnancy BMI and increasing gestational age. In analyses with BMI as a categorical variable, the Cox model and PAMM models yielded similar results. Analyses of BMI as a continuous variable also showed similar results when BMI associations were assumed to be linear, and the changes in gestational age-specific rates were modelled parametrically. However, results differed slightly when PAMMs, modelled with data-driven approaches, were used to estimate changes in BMI effects across gestational age; PAMMs provided a more nuanced modelling of time-varying effects. PAMM models showed an approximately linear increase in the effect of smoking on stillbirth with increasing gestational age.

CONCLUSIONS

For survival analyses using the foetuses-at-risk approach, PAMMs provide a valuable alternative to the traditional Cox model, with increased modelling flexibility when proportional hazards assumptions are violated.

Association between Endotype of Prematurity and Mortality: A Systematic Review, Meta-Analysis, and Meta-Regression

INTRODUCTION

Preterm birth represents the leading cause of neonatal mortality. Pathophysiological pathways, or endotypes, leading to prematurity can be clustered into infection/inflammation and dysfunctional placentation. We aimed to perform a systematic review and meta-analysis exploring the association between these endotypes and risk of mortality during first hospital admission Methods: PROSPERO ID: CRD42020184843. PubMed and Embase were searched for observational studies examining infants with gestational age (GA) ≤34 weeks. Chorioamnionitis represented the infectious-inflammatory endotype, while dysfunctional placentation proxies were hypertensive disorders of pregnancy (HDP) and small for GA (SGA)/intrauterine growth restriction (IUGR). A random-effects model was used to calculate odds ratios (ORs) and 95% confidence intervals. Heterogeneity was studied using random-effects meta-regression analysis.

RESULTS

Of 4,322 potentially relevant studies, 150 (612,580 infants) were included. Meta-analysis showed positive mortality odds for chorioamnionitis (OR: 1.43, 95% confidence interval: 1.25-1.62) and SGA/IUGR (OR: 1.68, 95% confidence interval: 1.38-2.04) but negative mortality odds for HDP (OR 0.74, 95% confidence interval: 0.64-0.86). Chorioamnionitis was associated with a lower GA, while HDP and SGA/IUGR were associated with a higher GA. Meta-regression showed a significant correlation between these differences in GA and mortality odds.

CONCLUSION

Our data suggest that the infectious/inflammatory endotype of prematurity has a greater overall impact on mortality risk as it is the most frequent endotype in the lower GAs. However, when the endotype of placental dysfunction is severe enough to induce growth restriction, it is strongly associated with higher mortality rates even though newborns are more mature.

Offspring school performance at age 12 after induction of labor vs non-intervention at term: A linked cohort study

INTRODUCTION

The incidence of induction of labor, for both medical reasons and as an elective procedure, has been rising and a further increase in induction of labor following the ARRIVE trial may be expected. The effects of induction of labor at term on childhood neurodevelopment, however, are not well studied. We aimed to study the influence of elective induction of labor for each week of gestation separately from 37 to 42 weeks on offspring school performance at 12 years of age after uncomplicated pregnancies.

MATERIAL AND METHODS

We performed a population-based study among 226 684 liveborn children from uncomplicated singleton pregnancies, born from 37⁺⁰ to 42⁺⁰  weeks of gestation in cephalic presentation in 2003-2008 (no hypertensive disorders, diabetes or birthweight ≤p5) in the Netherlands. Children with congenital anomalies, of non-white mothers and born after planned cesarean section were excluded. Birth records were linked with national data on school achievement. We compared, using a fetus-at-risk approach and per week of gestation, school performance score and secondary school level at age 12 in those born after induction of labor to those born after non-intervention, ie spontaneous onset of labor in the same week plus all those born at later gestations. Education scores were standardized to a mean of 0 and a standard deviation of 1 and adjusted in the regression analyses.

RESULTS

For each gestational age up to 41 weeks, induction of labor was associated with decreased school performance scores compared with non-intervention (at 37 weeks -0.05 SD, 95% confidence interval [CI] -0.10 to -0.01 SD; adjusted for confounding factors). After induction of labor, fewer children reached higher secondary school level (at 38 weeks 48% vs 54%; adjusted odds ratio [aOR] 0.88, 95% CI 0.82-0.94).

CONCLUSIONS

In women with uncomplicated pregnancies at term, consistently, at every week of gestation from 37 to 41 weeks, induction of labor is associated with lower offspring school performance at age 12 and lower secondary school level compared with non-intervention, although residual confounding may remain. These long-term effects of induction of labor should be incorporated in counseling and decision making.

Racial disparities in the development of comorbid conditions after preterm birth: A narrative review

Despite recognition and attempts to reduce racial disparities in perinatal outcomes, Black infants are still disproportionately represented among those who are born preterm. Postnatal investigations of racial disparities in comorbidities and outcomes after preterm birth are increasing, although their results and interpretations are conflicting. In the present review, we 1.) identify important methodological limitations of that literature 2.) summarize the conflicting literature investigating racial disparities, specifically Black-white differences, in postnatal comorbidities and outcomes after preterm birth 3.) describe mechanisms by which racism operates to contextualize our understanding to inform future work to actively reduce disparities in preterm birth and subsequently, its complications.

Perinatal mortality and neonatal and maternal outcome per gestational week in term pregnancies: A registry-based study

INTRODUCTION

Human pregnancy is considered term from 37+0/7 to 41+6/7 weeks. Within this range, both maternal, fetal and neonatal risks may vary considerably. This study investigates how gestational age per week is related to the components of perinatal mortality and parameters of adverse neonatal and maternal outcome at term.

MATERIAL AND METHODS

A registry-based study was made of all singleton term pregnancies in the Netherlands from January 2014 to December 2017. Stillbirth and early neonatal mortality, as components of perinatal mortality, were defined as primary outcomes; adverse neonatal and maternal events as secondary outcomes. Neonatal adverse outcomes included birth trauma, 5-minute Apgar score ≤3, asphyxia, respiratory insufficiency, neonatal intensive care unit admission and composite neonatal outcome. Maternal adverse outcomes included instrumental vaginal birth, emergency cesarean section, obstetric anal sphincter injury, postpartum hemorrhage, hypertensive disorders of pregnancy and composite maternal outcome. The primary outcomes were evaluated by comparing weekly prospective risks of stillbirth and neonatal death using a fetuses-at-risk approach. Secondly, odds ratios (OR) for perinatal mortality, adverse neonatal and maternal outcome using a births-based approach were compared for each gestational week with all births occurring after that week.

RESULTS

Data of 581 443 births were analyzed. At 37, 38, 39, 40, 41 and 42 weeks, the respective weekly prospective risks of stillbirth were 0.015%, 0.022%, 0.031%, 0.036%, 0.069% and 0.081%; the respective weekly prospective risks of early neonatal death were 0.051%, 0.047%, 0.032%, 0.031%, 0.039% and 0.035%. The OR for adverse neonatal outcomes were the lowest at 39 and 40 weeks. The OR for adverse maternal outcomes, including operative birth, continuously increased with each gestational week.

CONCLUSIONS

The prospective risk of early neonatal death for babies born at 39 weeks is lower than the risk of stillbirth in pregnancies continuing beyond 39+6/7 weeks. Birth at 39 weeks was associated with the best combined neonatal and maternal outcome, fewer operative births and fewer maternal and neonatal adverse outcomes compared with pregnancies continuing beyond 39 weeks. This information with appropriate perspectives should be included when counseling term pregnant women.

Fetal Maturation and Intrauterine Survival in Asian American Women by Ethnicity

OBJECTIVES

Although there are multiple ethnic subgroups of the Asian race, this population is usually treated as homogenous in public health research and practice. There is a dearth of information on fetal maturation and perinatal outcomes among Asian American women compared with their non-Hispanic (NH) White counterparts. This study aimed to determine whether fetal maturation, as captured by gestational age periods, influences the risk of stillbirth in Asian American fetuses, in general, as well as within different ethnic subgroups: Asian Indian, Korean, Chinese, Vietnamese, Japanese, and Filipino, using NH Whites as referent.

METHODS

We included singleton births within 37 to 44 gestational weeks occurring in Asian American and NH White mothers from 2014 to 2017. Adjusted logistic regression models were used to quantify the association between mother's race/ethnicity and risk of stillbirth by gestational age phenotypes: early-term, full-term, late-term, and postterm.

RESULTS

Compared with NH Whites, Asian Americans had 35% (adjusted odds ratio 0.65, 95% confidence interval 0.53-0.76) and 28% (adjusted odds ratio 0.72, 95% confidence interval 0.59-0.85) lower risk of early-term and full-term stillbirths, respectively.

CONCLUSIONS

Our study suggests the existence of differential maturation of the fetoplacental unit as explanation for the decline in intrauterine survival advantage with advancing gestational age among Asian American subgroups.

Maternal characteristics as indications for routine induction of labor: A nationwide retrospective cohort study

BACKGROUND

Maternal characteristics, such as parity and age, are increasingly considered indications for routine induction of labor of otherwise healthy women to prevent fetal and neonatal mortality. To fully balance the risks and benefits of induction of labor, we examined the association of additional relevant maternal characteristics and gestational age with fetal and neonatal mortality.

METHODS

We conducted a nationwide retrospective cohort study among a healthy Dutch population consisting of all singleton pregnancies in midwife-led care after 37 weeks of gestation in the period 2000-2018. We examined the association of maternal ethnicity, age, parity, and socioeconomic status with fetal and neonatal mortality, stratified by gestational age. The association of single characteristics was examined using descriptive statistics, and univariable and multivariable logistics regression analyses. The associations of multiple characteristics were examined using inter-categorical analyses and using interaction terms in the multivariable logistic regression analyses.

RESULTS

The results showed that ethnicity, age, parity, socioeconomic status, and gestational age did not act as single determinant of fetal and neonatal mortality. The probability of fetal and neonatal mortality differed among subgroups of women depending on which determinants were considered and the number of determinants included.

CONCLUSIONS

Decision-making about induction of labor to prevent fetal and neonatal mortality based on a single determinant may lead to overuse or underuse of IOL. A value-based health care strategy, addressing social inequity, and investing in better screening and diagnostic methods that employ an individualized and multi-determinant approach may be more effective at preventing fetal and neonatal mortality.

The Global Pregnancy Collaboration (CoLab) symposium on short- and long-term outcomes in offspring whose mothers had preeclampsia: A scoping review of clinical evidence

Preeclampsia is a maternal syndrome characterized by the new onset of hypertension after 20 weeks of gestation associated with multisystemic complications leading to high maternal and fetal/neonatal morbidity and mortality. However, sequelae of preeclampsia may extend years after pregnancy in both mothers and their children. In addition to the long-term adverse cardiovascular effects of preeclampsia in the mother, observational studies have reported elevated risk of cardiovascular, metabolic, cerebral and cognitive complications in children born from women with preeclampsia. Less clear is whether the association between maternal preeclampsia and offspring sequelae are causal, or to what degree the associations might be driven by fetal factors including impaired growth and the health of its placenta. Our discussion of these complexities in the 2018 Global Pregnancy Collaboration annual meeting prompted us to write this review. We aimed to summarize the evidence of an association between maternal preeclampsia and neurobehavioral developmental disorders in offspring in hopes of generating greater research interest in this important topic.

Time trend analysis of perinatal mortality, stillbirth, and early neonatal mortality of multiple pregnancies for each gestational week from the year 2000 to 2019: A population-based study in Japan

Multiple pregnancies pose a high risk of morbidity and mortality in both mothers and infants; thus, obtaining reliable information based on a large population is essential to improve management. We used the maternal and child health statistics, which are published annually, from the database of the Ministry of Health, Labor, and Welfare. The data obtained were aggregated in 5-year intervals, and we used them to analyze the proportion of the number of births for each week of pregnancy to the total of each singleton and multiple pregnancy. For perinatal health indicators (perinatal mortality, stillbirth, and neonatal mortality), the obtained data were calculated and plotted on graphs for each week of pregnancy. Moreover, these indicators were calculated by dividing them into first twin and second twin fetuses. Stillbirth weights were aggregated in several groups, and a histogram was displayed. Between 2000 and 2019, there were 21,068,275 live births, 67,666 stillbirths, and 16,443 early neonatal deaths, excluding 7,148 (7,104 singletons, 44 multiple births) cases, in which the exact gestational weeks at birth were unknown. More than 95% of multiple pregnancies were twin births. Perinatal mortality, stillbirth, and early neonatal mortality rates in multiple pregnancies were the lowest at approximately 37 weeks of gestation and lower than those of single pregnancies at approximately 36 weeks of gestation. Perinatal mortality and stillbirth rates were higher during the delivery of the second twins than the first-born twins, but the early neonatal mortality rate remained approximately the same during the delivery of both twins. As the data in the government database are accumulated and published continuously, indicators can be calculated in the future using the method presented in this study. Further, our findings may be useful for policymaking related to managing multiple pregnancies.

The association between pre-pregnancy body mass index and perinatal death and the role of gestational age at delivery

Introduction

The pathophysiology behind the association between obesity and perinatal death is not fully understood but may be in part due to higher rates of pregnancy complications at earlier gestation amongst obese women. We aimed to quantify the proportion of perinatal deaths amongst obese and overweight women mediated by gestational age at stillbirth or live birth.

Methods

The study included all singleton births at ≥20 weeks’ gestation in British Columbia, 2004–2017, and excluded pregnancy terminations. The proportion of the association between BMI and perinatal death mediated by gestational age at delivery (in weeks) was estimated using natural effect models, with adjustment for potential confounders. Sensitivity analyses for unmeasured confounding and women missing BMI were conducted.

Results

Of 392,820 included women, 20.6% were overweight and 12.8% obese. Women with higher BMI had a lower gestational age at delivery. Perinatal mortality was 0.5% (1834 pregnancies); and was elevated in overweight (adjusted odds ratio [AOR] = 1.22, 95% confidence interval [CI] 1.08–1.37) and obese women (AOR = 1.55, 95% CI 1.36–1.77). Mediation analysis showed that 63.1% of the association between obesity and perinatal death was mediated by gestational age at delivery (natural indirect effect AOR = 1.32, 95% CI 1.23–1.42, natural direct effect AOR = 1.18, 95% CI 1.05–1.32). Similar, but smaller effects were seen when comparing overweight women vs. women with a normal BMI. Estimated effects were not affected by adjustment for additional risk factors for perinatal death or sensitivity analyses for missing data.

Conclusion

Obese pregnancies have a higher risk of perinatal death in part mediated by a lower gestational age at delivery.

Should twin-specific growth charts be used to assess fetal growth in twin pregnancies?

One of the hallmarks of twin pregnancies is the slower rate of fetal growth when compared with singleton pregnancies during the third trimester. The mechanisms underlying this phenomenon and whether it represents pathology or benign physiological adaptation are currently unclear. One important implication of these questions relates to the type growth charts that should be used by care providers to monitor growth of twin fetuses. If the slower growth represents pathology (ie, intrauterine growth restriction caused uteroplacental insufficiency), it would be preferable to use a singleton growth chart to identify a small twin fetus that is at risk for perinatal mortality and morbidity. If, however, the relative smallness of twins is the result of benign adaptive mechanisms, it is likely preferable to use a twin-based charts to avoid overdiagnosis of intrauterine growth restriction in twin pregnancies. In the current review, we addressed this question by describing the differences in fetal growth between twin and singleton pregnancies, reviewing the current knowledge regarding the mechanisms responsible for slower fetal growth in twins, summarizing available empirical evidence on the diagnostic accuracy of the 2 types of charts for intrauterine growth restriction in twin pregnancies, and addressing the question of whether uncomplicated dichorionic twins are at an increased risk for fetal death when compared with singleton fetuses. We identified a growing body of evidence that shows that the use of twin charts can reduce the proportion of twin fetuses identified with suspected intrauterine growth restriction by up to 8-fold and can lead to a diagnosis of intrauterine growth restriction that is more strongly associated with adverse perinatal outcomes and hypertensive disorders than a diagnosis of intrauterine growth restriction based on a singleton-based chart without compromising the detection of twin fetuses at risk for adverse outcomes caused by uteroplacental insufficiency. We further found that small for gestational age twins are less likely to experience adverse perinatal outcomes or to have evidence of uteroplacental insufficiency than small for gestational age singletons and that recent data question the longstanding view that uncomplicated dichorionic twins are at an increased risk for fetal death caused by placental insufficiency. Overall, it seems that, based on existing evidence, the of use twin charts is reasonable and may be preferred over the use of singleton charts when monitoring the growth of twin fetuses. Still, it is important to note that the available data have considerable limitations and are primarily derived from observational studies. Therefore, adequately-powered trials are likely needed to confirm the benefit of twin charts before their use is adopted by professional societies.

Quality of Care in US NICUs by Race and Ethnicity

BACKGROUND

Summary measures are used to quantify a hospital's quality of care by combining multiple metrics into a single score. We used Baby-MONITOR, a summary quality measure for NICUs, to evaluate quality by race and ethnicity across and within NICUs in the United States.

METHODS

Vermont Oxford Network members contributed data from 2015 to 2019 on infants from 25 to 29 weeks' gestation or of 401 to 1500 g birth weight who were inborn or transferred to the reporting hospital within 28 days of birth. Nine Baby-MONITOR measures were individually risk adjusted, standardized, equally weighted, and averaged to derive scores for African American, Hispanic, Asian American, and American Indian infants, compared with white infants.

RESULTS

This prospective cohort included 169 400 infants at 737 hospitals. Across NICUs, Hispanic and Asian American infants had higher Baby-MONITOR summary scores, compared with those of white infants. African American and American Indian infants scored lower on process measures, and all 4 minority groups scored higher on outcome measures. Within NICUs, the mean summary scores for African American, Hispanic, and Asian American NICU subsets were higher, compared with those of white infants in the same NICU. American Indian summary NICU scores were not different, on average.

CONCLUSIONS

With Baby-MONITOR, we identified differences in NICU quality by race and ethnicity. However, the summary score masked within-measure quality gaps that raise unanswered questions about the relationships between race and ethnicity and processes and outcomes of care.

Pregnancy outcomes during the COVID-19 pandemic in Canada, March to August 2020

OBJECTIVE

Several studies have documented changes in the rates preterm birth and stillbirth during the COVID-19 pandemic. We carried out a study to examine obstetric intervention, preterm birth, and stillbirth rates in Canada from March to August 2020.

METHODS

The study included all singleton hospital deliveries in Canada (excluding Québec) from March to August 2020 (and March to August for the years 2015-2019) with information obtained from the Canadian Institute for Health Information. Data for Ontario were examined separately because this province had the highest rates of COVID-19 in the study population. Rates and odds ratios with 95% confidence intervals (CIs) were used to quantify pregnancy-related outcomes.

RESULTS

There were 136,445 and 717,905 singleton hospital deliveries in Canada (excluding Quebéc) in from March to August 2020 and between March and August 2015-2019, respectively. Rates of obstetric intervention declined in early gestation in 2020. Odds ratios for labour induction and cesarean delivery at <32 weeks gestation for March-August 2020 versus March-August in 2015 to 2019 were 0.84 (95% CI 0.74-0.95) and 0.92 (95% CI 0.85-1.00), respectively. Preterm birth rates increased in Canada (excluding Québec) from 6.42% in March-August 2015 to 6.74% in March-August 2019 but were unchanged in March-August 2020 (6.74%). Stillbirth rates were stable between March-August 2015 and March-August 2020. However, stillbirth rates peaked in Ontario in April 2020 due to higher rates of stillbirths at 20-27 and 37-41 weeks gestation.

CONCLUSION

Changes in labour induction and cesarean delivery at early gestation and other perinatal outcomes during the period of March to August 2020 highlight the need to reconsider the use and impact of obstetric services in pandemics as well as the need for timely perinatal surveillance.

Stillbirth as left truncation for early neonatal death in California, 1989-2015: a time-series study

BACKGROUND

Some scholars posit that attempts to avert stillbirth among extremely preterm gestations may result in a live birth but an early neonatal death. The literature, however, reports no empirical test of this potential form of left truncation. We examine whether annual cohorts delivered at extremely preterm gestational ages show an inverse correlation between their incidence of stillbirth and early neonatal death.

METHODS

We retrieved live birth and infant death information from the California Linked Birth and Infant Death Cohort Files for years 1989 to 2015. We defined the extremely preterm period as delivery from 22 to < 28 weeks of gestation and early neonatal death as infant death at less than 7 days of life. We calculated proportions of stillbirth and early neonatal death separately by cohort year, race/ethnicity, and sex. Our correlational analysis controlled for well-documented declines in neonatal mortality over time.

RESULTS

California reported 89,276 extremely preterm deliveries (live births and stillbirths) to Hispanic, non-Hispanic (NH) Black, and NH white mothers from 1989 to 2015. Findings indicate an inverse correlation between stillbirth and early neonatal death in the same cohort year (coefficient: -0.27, 95% CI of - 0.11; - 0.42). Results remain robust to alternative specifications and falsification tests.

CONCLUSIONS

Findings support the notion that cohorts with an elevated risk of stillbirth also show a reduced risk of early neonatal death among extremely preterm deliveries. Results add to the evidence base that selection in utero may influence the survival characteristics of live-born cohorts.

Bias in comparisons of mortality among very preterm births: A cohort study

BACKGROUND

Several studies of prenatal determinants and neonatal morbidity and mortality among very preterm births have resulted in unexpected and paradoxical findings. We aimed to compare perinatal death rates among cohorts of very preterm births (24-31 weeks) with rates among all births in these groups (≥24 weeks), using births-based and fetuses-at-risk formulations.

METHODS

We conducted a cohort study of singleton live births and stillbirths ≥24 weeks' gestation using population-based data from the United States and Canada (2006-2015). We contrasted rates of perinatal death between women with or without hypertensive disorders, between maternal races, and between births in Canada vs the United States.

RESULTS

Births-based perinatal death rates at 24-31 weeks were lower among hypertensive than among non-hypertensive women (rate ratio [RR] 0.67, 95% CI 0.65-0.68), among Black mothers compared with White mothers (RR 0.94, 95%CI 0.92-0.95) and among births in the United States compared with Canada (RR 0.74, 95%CI 0.71-0.75). However, overall (≥24 weeks) perinatal death rates were higher among births to hypertensive vs non-hypertensive women (RR 2.14, 95%CI 2.10-2.17), Black vs White mothers (RR 1.86, 95%CI 184-1.88;) and births in the United States vs Canada (RR 1.08, 95%CI 1.05-1.10), as were perinatal death rates based on fetuses-at-risk at 24-31 weeks (RR for hypertensive disorders: 2.58, 95%CI 2.53-2.63; RR for Black vs White ethnicity: 2.29, 95%CI 2.25-2.32; RR for United States vs Canada: 1.27, 95%CI 1.22-1.30).

CONCLUSION

Studies of prenatal risk factors and between-centre or between-country comparisons of perinatal mortality bias causal inferences when restricted to truncated cohorts of very preterm births.

Incidence and risk of stillbirth among various Asian-American subgroups

BACKGROUND

Striking racial/ethnic disparities exist in pregnancy outcomes among various racial/ethnic.

OBJECTIVE

To determine the incidence and risk factors associated with stillbirth in Asian-American women.

STUDY DESIGN

We conducted this retrospective cohort study using the United States Birth and Fetal Death data files 2014-2017. We used the fetuses-at-risk approach to generate stillbirth trends by gestational age among Non-Hispanic (NH)-White and Asian-American births during the study period. We calculated the adjusted risk of stillbirth for Asian-Americans, overall, and for each Asian-American subgroup: Asian Indians, Koreans, Chinese, Vietnamese, Japanese and Filipinos, with NH-Whites as the referent category.

RESULTS

Of the 715,297 births that occurred among Asian-Americans during the study period, stillbirth incidence rate was 3.86 per 1000 births. From the gestational age of 20 weeks through 41 weeks, the stillbirth rates were consistently lower among Asian-Americans compared to NH-Whites. Stillbirth incidence ranged from a low rate of 2.6 per 1000 births in Koreans to as high as 5.3 per 1000 births in Filipinos. After adjusting for potentially confounding characteristics, Asian-Americans were about half as likely to experience stillbirth compared to NH-White mothers [adjusted hazards ratio (AHR) = 0.57, 95% confidence interval (CI) = 0.51-0.64]. This intrauterine survival advantage was evident in all Asian-American subgroups.

CONCLUSION

The risk of stillbirth is twofold lower in Asian-Americans than in NH-Whites. It will be an important research agenda to determine reasons for the improved intrauterine survival among Asian-Americans in order to uncover clues for reducing the burden of stillbirth among other racial/ethnic minority women in the United States.

Cause-Specific Stillbirth and Neonatal Death According to Prepregnancy Obesity and Early Gestational Weight Gain: A Study in the Danish National Birth Cohort

Maternal obesity is associated with impaired fetal and neonatal survival, but underlying mechanisms are poorly understood. We examined how prepregnancy BMI and early gestational weight gain (GWG) were associated with cause-specific stillbirth and neonatal death. In 85,822 pregnancies in the Danish National Birth Cohort (1996–2002), we identified causes of death from medical records for 272 late stillbirths and 228 neonatal deaths. Prepregnancy BMI and early GWG derived from an early pregnancy interview and Cox regression were used to estimate associations with stillbirth or neonatal death as a combined outcome and nine specific cause-of-death categories. Compared to women with normal weight, risk of stillbirth or neonatal death was increased by 66% with overweight and 78% with obesity. Especially deaths due to placental dysfunction, umbilical cord complications, intrapartum events, and infections were increased in women with obesity. More stillbirths and neonatal deaths were observed in women with BMI < 25 and low GWG. Additionally, unexplained intrauterine death was increased with low GWG, while more early stillbirths were seen with both low and high GWG. In conclusion, causes of death that relate to vascular and metabolic disturbances were increased in women with obesity. Low early GWG in women of normal weight deserves more clinical attention.

Maternal body mass index in early pregnancy and severe asphyxia-related complications in preterm infants

BACKGROUND

Little is known about the associations between maternal body mass index (BMI) and asphyxia-related morbidity in preterm infants (<37 weeks). We aimed to investigate associations between maternal BMI in early pregnancy and severe asphyxia-related neonatal complications in preterm infants (<37 weeks) and to examine whether possible associations were mediated by overweight- or obesity-related complications.

METHODS

In this Swedish population-based cohort of 62 499 singleton non-malformed preterm infants born from 1997 to 2011, risks of low Apgar scores (0-3) at 5 and 10 minutes, neonatal seizures and intraventricular haemorrhage (IVH) were estimated through two analytical approaches. In the conventional approach, the denominator for risk was all live births at a given gestational age. In the fetuses-at-risk (FAR) approach, the denominator for risk was ongoing pregnancies at a given gestational age.

RESULTS

Using the conventional approach, adjusted risk ratios per 10-unit BMI increase were 1.32 [95% confidence interval (CI) 1.13-1.54] and 1.37 (95% CI 1.12-1.67) for low Apgar scores at 5 and 10 minutes, respectively; 1.28 (95% CI 1.00-1.65) for neonatal seizures; and 1.18 (95% CI 1.01-1.37) for IVH. Using the FAR approach, corresponding risks were higher. These associations varied by gestational age (<32 and 32-36 weeks). Associations between maternal BMI and asphyxia-related outcomes were partly mediated through lower gestational age.

CONCLUSIONS

Increasing maternal BMI in early pregnancy is associated with increased risks of severe asphyxia-related complications in preterm infants. Our findings add to the evidence to support interventions to reduce obesity in woman of reproductive age.

I can't breathe

The phrase "I can't breathe" has become a national slogan in recent months for those who are protesting against racial discrimination across the world. For clinicians caring for neonates, this phrase should serve as a reminder about the stark disparities in health outcomes and health services for black infants and their families that have persisted for decades in spite of a voluminous amount of literature describing these disparities and the factors contributing to them. It should galvanize us into action within the neonatal intensive care unit and beyond to ensure equal treatment for all patients and their families, and to take measures to compensate for the disparities.

The Robson classification for caesarean section-A proposed method based on routinely collected health data

BACKGROUND

With an increasing rate of caesarean sections as well as rising numbers of multiple pregnancies, valid classifications for benchmarking are needed. The Robson classification provides a method to group cases with caesarean section in order to assess differences in outcome across regions and sites. In this study we set up a novel method of classification by using routinely collected health data. We hypothesize i that routinely collected health data can be used to apply complex medical classifications and ii that the Robson classification is capable of classifying mothers and their corresponding newborn into meaningful groups with regard to outcome.

METHODS AND FINDINGS

The study was conducted at the coding department and the department of obstetrics and gynecology Inselspital, University Hospital of Bern, Switzerland. The study population contained inpatient cases from 2014 until 2017. Administrative and health data were extracted from the Data Warehouse. Cases were classified by a Structured Query Language code according to the Robson criteria using data from the administrative system, the electronic health record and from the laboratory system. An automated query to classify the cases according to Robson could be implemented and successfully validated. A linkage of the mother's class to the corresponding newborn could be established. The distribution of clinical indicators was described. It could be shown that the Robson classes are associated to outcome parameters and case related costs.

CONCLUSIONS

With this study it could be demonstrated, that a complex query on routinely collected health data would serve for medical classification and monitoring of quality and outcome. Risk-stratification might be conducted using this data set and should be the next step in order to evaluate the Robson criteria and outcome. This study will enhance the discussion to adopt an automated classification on routinely collected health data for quality assurance purposes.

A compelling symmetry: The extended fetuses-at-risk perspective on modal, optimal and relative birthweight and gestational age

BACKGROUND

The relationship between several intriguing perinatal phenomena, namely, modal, optimal, and relative birthweight and gestational age, remains poorly understood, especially the mechanism by which relative birthweight and gestational age resolve the paradox of intersecting perinatal mortality curves.

METHODS

Birthweight and gestational age distributions and birthweight- and gestational age-specific perinatal death rates of low- and high-risk cohorts in the United States, 2004-2015, were estimated using births-based and extended fetuses-at-risk formulations. The relationships between these births-based distributions and rates, and the first derivatives of fetuses-at-risk birth and perinatal death rates were examined in order to assess how the rate of change in fetuses-at-risk rates affects gestational age distributions and births-based perinatal death rate patterns.

RESULTS

Modal gestational age typically exceeded optimal gestational age because both were influenced by the peak in the first derivative of the birth rate, while optimal gestational age was additionally influenced by the point at which the first derivative of the fetuses-at-risk perinatal death rate showed a sharp increase in late gestation. The clustering and correlation between modal and optimal gestational age within cohorts, the higher perinatal death rate at optimal gestational age among higher-risk cohorts, and the symmetric left-shift in births-based gestational age-specific perinatal death rates in higher-risk cohorts explained how relative gestational age resolved the paradox of intersecting perinatal mortality curves.

CONCLUSIONS

Changes in the first derivative of the fetuses-at-risk birth and perinatal death rates underlie several births-based perinatal phenomena and this explanation further unifies the fetuses-at-risk and births-based models of perinatal death.

The Effect of Prenatal Treatments on Offspring Events in the Presence of Competing Events: An Application to a Randomized Trial of Fertility Therapies

When studying the effect of a prenatal treatment on events in the offspring, failure to produce a live birth is a competing event for events in the offspring. A common approach to handle this competing event is reporting both the treatment-specific probabilities of live births and of the event of interest among live births. However, when the treatment affects the competing event, the latter probability cannot be interpreted as the causal effect among live births. Here we provide guidance for researchers interested in the effects of prenatal treatments on events in the offspring in the presence of the competing event "no live birth." We review the total effect of treatment on a composite event and the total effect of treatment on the event of interest. These causal effects are helpful for decision making but are agnostic about the pathways through which treatment affects the event of interest. Therefore, based on recent work, we also review three causal effects that explicitly consider the pathways through which treatment may affect the event of interest in the presence of competing events: the direct effect of treatment on the event of interest under an intervention to eliminate the competing event, the separable direct and indirect effects of treatment on the event of interest, and the effect of treatment in the principal stratum of those who would have had a live birth irrespective of treatment choice. As an illustrative example, we use a randomized trial of fertility treatments and risk of neonatal complications.

Stillbirths and live births in the periviable period

PURPOSE

We use data from California, where 13% of US births occur, to address two questions arising from efforts in the first decade of this century to avoid stillbirths before 25 6/7 weeks of gestation (i.e., in the periviable period). First, did stillbirths decline in the first decade of this century? Second, if stillbirths did decline, did periviable live births increase simultaneously? Answering these questions is important given that periviable infants represent less than 1% of live births but account for roughly 40% of infant mortality and 20% of hospital-based obstetric costs in the United States.

METHODS

We constructed 240 monthly conception cohorts, starting with that conceived in January 1991, from 9,880,536 singleton pregnancies that reached the 20 0/7 week of gestation. We used time-series design and Box-Jenkins methods that address confounding by autocorrelation, including secular trends and seasonality to answer our questions.

RESULTS

We detected a downward shift in stillbirths in April 2007 that coincided with an upward shift in periviable live births.

CONCLUSIONS

Our findings imply that, since 2007, fewer Californians than expected from history and from the size of conception cohorts reaching 20 0/7 weeks of gestation have had to contend with the sequelae of stillbirths, but more than expected likely have had to contend with those of periviable births.

Phenotypes of fetal macrosomia and risk of stillbirth among term deliveries over the previous four decades

OBJECTIVES

To evaluate the association between macrosomia and stillbirth over the previous four decades and to determine the consistency of the relationship.

METHODS

This was a population-based retrospective cohort study using United States Natality and Fetal Death Data from 1982 to 2017 and restricted to the gestational age range of 37-41 weeks inclusive. Macrosomia was defined as birthweight ≥4000 g and subdivided into its grades as previously recommended: grade 1 (4000-4499 g), grade 2 (4500-4999 g), and grade 3 (≥5000 g). We calculated temporal trends of stillbirth among fetuses with macrosomia over the years using joinpoint regression. We generated odds ratios from adjusted binomial logistic regression models to examine the association between macrosomia and risk of stillbirth stratified by grades using normal-weight infants (2500-3999 g) as referent.

RESULTS

Within the fetal macrosomia group, the rate of stillbirth declined from 2.04/1000 in 1982 to 1.05/1000 by the end of the study period (2017), representing a drop of about 48.5%. For the normal-weight fetuses, stillbirth rate declined from 1.95/1000 to 0.83/1000, equivalent to a decline of 57.4%. Macrosomia was significantly associated with elevated risk for stillbirth: grade 2 (OR = 1.27; 95% CI = 1.22-1.32) and grade 3 (OR = 5.97; 95% CI = 5.69-6.22).

CONCLUSIONS

Fetal macrosomia is a significant risk factor for fetal demise with the worst intrauterine survival observed among those classified as grade 3. Fetal macrosomia is a heterogeneous rather than a homogeneous entity in terms of risk profiles, and this needs to be considered in future policy guidelines.

Intensity of perinatal care for extremely preterm babies and outcomes at a higher gestational age: evidence from the EPIPAGE-2 cohort study

Background

Perinatal decision-making affects outcomes for extremely preterm babies (22–26 weeks’ gestational age (GA)): more active units have improved survival without increased morbidity. We hypothesised such units may gain skills and expertise meaning babies at higher gestational ages have better outcomes than if they were born elsewhere. We examined mortality and morbidity outcomes at age two for babies born at 27–28 weeks’ GA in relation to the intensity of perinatal care provided to extremely preterm babies.

Methods

Fetuses from the 2011 French national prospective EPIPAGE-2 cohort, alive at maternal admission to a level 3 hospital and delivered at 27–28 weeks’ GA, were included. Morbidity-free survival (survival without sensorimotor (blindness, deafness or cerebral palsy) disability) and overall survival at age two were examined. Sensorimotor disability and Ages and Stages Questionnaire (ASQ) result below threshold among survivors were secondary outcomes. Perinatal care intensity level was based on birth hospital, grouped using the ratio of 24–25 weeks’ GA babies admitted to neonatal intensive care to fetuses of the same gestation alive at maternal admission. Sensitivity analyses used ratios based upon antenatal steroids, Caesarean section, and newborn resuscitation. Multiple imputation was used for missing data; hierarchical logistic regression accounted for births nested within centres.

Results

633 of 747 fetuses (84.7%) born at 27–28 weeks’ GA survived to age two. There were no differences in survival or morbidity-free survival: respectively, fully adjusted odds ratios were 0.96 (95% CI: 0.54 to 1.71) and 1.09 (95% CI: 0.59 to 2.01) in medium and 1.12 (95% CI: 0.63 to 2.00) and 1.16 (95% CI: 0.62 to 2.16) in high compared to low-intensity hospitals. Among survivors, there were no differences in sensorimotor disability or ASQ below threshold. Sensitivity analyses were consistent with the main results.

Conclusions

No difference was seen in survival or morbidity-free survival at two years of age among fetuses alive at maternal hospital admission born at 27–28 weeks’ GA, or in sensorimotor disability or presence of an ASQ below threshold among survivors. There is no evidence for an impact of intensity of perinatal care for extremely preterm babies on births at a higher gestational age.

The fragile foundations of the extended fetuses-at-risk approach

BACKGROUND

Whether denominators for postnatal outcomes (ascertained after live birth) with a presumed prenatal origin should consist of fetuses or live births remains controversial. Proponents argue that the extended fetuses-at-risk (FAR) approach (a), provides a justification for medically indicated preterm delivery, (b), avoids paradoxical results, and (c), permits quantification of incidence of fetal-infant phenomena, such as "revealed" small for gestational age (SGA)-which, under FAR, rises with advancing gestation.

METHODS

This conceptual paper examines the validity of the above arguments.

RESULTS

As obstetricians induce babies early because of fetal (or maternal) compromise and despite the dangers posed by immaturity, there is no need to modify a paradigm that portrays preterm birth as a powerful risk factor. The FAR approach generally avoids "paradoxical" intersections because FAR rates of postnatal outcomes depend on the birth rate. However, this property, which causes rates of most postnatal outcomes to rise at term, can also lead to risk reversals and other misleading findings. The FAR formulation does not yield the incidence of postnatal conditions but, rather, the incidence of live birth (and survival to diagnosis) of babies with prevalent conditions (and, sometimes, future ones).

CONCLUSIONS

The proposed arguments do not provide adequate support for extending the FAR approach to postnatal outcomes. As only live births can contribute to the numerator of rates, the usefulness and interpretability of FAR measures in this setting are limited.

Associations of Maternal Cell-Phone Use During Pregnancy With Pregnancy Duration and Fetal Growth in 4 Birth Cohorts

Results from studies evaluating potential effects of prenatal exposure to radio-frequency electromagnetic fields from cell phones on birth outcomes have been inconsistent. Using data on 55,507 pregnant women and their children from Denmark (1996-2002), the Netherlands (2003-2004), Spain (2003-2008), and South Korea (2006-2011), we explored whether maternal cell-phone use was associated with pregnancy duration and fetal growth. On the basis of self-reported number of cell-phone calls per day, exposure was grouped as none, low (referent), intermediate, or high. We examined pregnancy duration (gestational age at birth, preterm/postterm birth), fetal growth (birth weight ratio, small/large size for gestational age), and birth weight variables (birth weight, low/high birth weight) and meta-analyzed cohort-specific estimates. The intermediate exposure group had a higher risk of giving birth at a lower gestational age (hazard ratio = 1.04, 95% confidence interval: 1.01, 1.07), and exposure-response relationships were found for shorter pregnancy duration (P < 0.001) and preterm birth (P = 0.003). We observed no association with fetal growth or birth weight. Maternal cell-phone use during pregnancy may be associated with shorter pregnancy duration and increased risk of preterm birth, but these results should be interpreted with caution, since they may reflect stress during pregnancy or other residual confounding rather than a direct effect of cell-phone exposure.

Understanding the relation between Zika virus infection during pregnancy and adverse fetal, infant and child outcomes: a protocol for a systematic review and individual participant data meta-analysis of longitudinal studies of pregnant women and their infants and children

INTRODUCTION

Zika virus (ZIKV) infection during pregnancy is a known cause of microcephaly and other congenital and developmental anomalies. In the absence of a ZIKV vaccine or prophylactics, principal investigators (PIs) and international leaders in ZIKV research have formed the ZIKV Individual Participant Data (IPD) Consortium to identify, collect and synthesise IPD from longitudinal studies of pregnant women that measure ZIKV infection during pregnancy and fetal, infant or child outcomes.

METHODS AND ANALYSIS

We will identify eligible studies through the ZIKV IPD Consortium membership and a systematic review and invite study PIs to participate in the IPD meta-analysis (IPD-MA). We will use the combined dataset to estimate the relative and absolute risk of congenital Zika syndrome (CZS), including microcephaly and late symptomatic congenital infections; identify and explore sources of heterogeneity in those estimates and develop and validate a risk prediction model to identify the pregnancies at the highest risk of CZS or adverse developmental outcomes. The variable accuracy of diagnostic assays and differences in exposure and outcome definitions means that included studies will have a higher level of systematic variability, a component of measurement error, than an IPD-MA of studies of an established pathogen. We will use expert testimony, existing internal and external diagnostic accuracy validation studies and laboratory external quality assessments to inform the distribution of measurement error in our models. We will apply both Bayesian and frequentist methods to directly account for these and other sources of uncertainty.

ETHICS AND DISSEMINATION

The IPD-MA was deemed exempt from ethical review. We will convene a group of patient advocates to evaluate the ethical implications and utility of the risk stratification tool. Findings from these analyses will be shared via national and international conferences and through publication in open access, peer-reviewed journals.

TRIAL REGISTRATION NUMBER

PROSPERO International prospective register of systematic reviews (CRD42017068915).

Towards a unified perinatal theory: Reconciling the births-based and fetus-at-risk models of perinatal mortality

BACKGROUND

There is a need to reconcile the opposing perspectives of the births-based and fetuses-at-risk models of perinatal mortality and to formulate a coherent and unified perinatal theory.

METHODS

Information on births in the United States from 2004 to 2015 was used to calculate gestational age-specific perinatal death rates for low- and high-risk cohorts. Cubic splines were fitted to the fetuses-at-risk birth and perinatal death rates, and first and second derivatives were estimated. Births-based perinatal death rates, and fetuses-at-risk birth and perinatal death rates and their derivatives, were examined to identify potential inter-relationships.

RESULTS

The rate of change in the birth rate dictated the pattern of births-based perinatal death rates in a triphasic manner: increases in the first derivative of the birth rate at early gestation corresponded with exponential declines in perinatal death rates, the peak in the first derivative presaged the nadir in perinatal death rates, and late gestation declines in the first derivative coincided with an upturn in perinatal death rates. Late gestation increases in the first derivative of the fetuses-at-risk perinatal death rate matched the upturn in births-based perinatal death rates. Differences in birth rate acceleration/deceleration among low- and high-risk cohorts resulted in intersecting perinatal mortality curves.

CONCLUSION

The first derivative of the birth rate links a cohort's fetuses-at-risk perinatal death rate to its births-based perinatal death rate, and cohort-specific differences in birth rate acceleration/deceleration are responsible for the intersecting perinatal mortality curves paradox. This mechanistic explanation unifies extant models of perinatal mortality and provides diverse insights.

Intensity of perinatal care, extreme prematurity and sensorimotor outcome at 2 years corrected age: evidence from the EPIPAGE-2 cohort study

BACKGROUND

Emerging evidence suggests intensity of perinatal care influences survival for extremely preterm babies. We evaluated the effect of differences in perinatal care intensity between centres on sensorimotor morbidity at 2 years of age. We hypothesised that hospitals with a higher intensity of perinatal care would have improved survival without increased disability.

METHODS

Foetuses alive at maternal admission to a level 3 hospital in France in 2011, subsequently delivered between 22 and 26 weeks gestational age (GA) and included in the EPIPAGE-2 national prospective observational cohort study formed the baseline population. Level of intensity of perinatal care was assigned according to hospital of birth, categorised into three groups using 'perinatal intensity' ratios (ratio of 24-25 weeks GA babies admitted to neonatal intensive care to foetuses of the same GA alive at maternal admission to hospital). Multiple imputation was used to account for missing data; hierarchical logistic regression accounting for births nested within centres was then performed.

RESULTS

One thousand one hundred twelve foetuses were included; 473 survived to 2 years of age (126 of 358 in low-intensity, 140 of 380 in medium-intensity and 207 of 374 in high-intensity hospitals). There were no differences in disability (adjusted odds ratios 0.93 (95% CI 0.28 to 3.04) and 1.04 (95% CI 0.34 to 3.14) in medium- and high- compared to low-intensity hospitals, respectively). Compared to low-intensity hospitals, survival without sensorimotor disability was increased in the population of foetuses alive at maternal admission to hospital and in live-born babies, but there were no differences when considering only babies admitted to NICU or survivors.

CONCLUSIONS

No difference in sensorimotor outcome for survivors of extremely preterm birth at 2 years of age was found according to the intensity of perinatal care provision. Active management of periviable births was associated with increased survival without sensorimotor disability.

The curse of the perinatal epidemiologist: inferring causation amidst selection

Purpose of review

Human reproduction is a common process and one that unfolds over a relatively short time, but pregnancy and birth processes are challenging to study. Selection occurs at every step of this process (e.g., infertility, early pregnancy loss, and stillbirth), adding substantial bias to estimated exposure-outcome associations. Here we focus on selection in perinatal epidemiology, specifically, how it affects research question formulation, feasible study designs, and interpretation of results.

Recent findings

Approaches have recently been proposed to address selection issues in perinatal epidemiology. One such approach is the ongoing pregnancies denominator for gestation-stratified analyses of infant outcomes. Similarly, bias resulting from left truncation has recently been termed "live birth bias," and a proposed solution is to control for common causes of selection variables (e.g., fecundity, fetal loss) and birth outcomes. However, these approaches have theoretical shortcomings, conflicting with the foundational epidemiologic concept of populations at risk for a given outcome.

Summary

We engage with epidemiologic theory and employ thought experiments to demonstrate the problems of using denominators that include units not "at risk" of the outcome. Fundamental (and commonsense) concerns of outcome definition and analysis (e.g., ensuring that all study participants are at risk for the outcome) should take precedence in formulating questions and analysis approach, as should choosing questions that stakeholders care about. Selection and resulting biases in human reproductive processes complicate estimation of unbiased exposure- outcome associations, but we should not focus solely (or even mostly) on minimizing such biases.

Association of participation in a supplemental nutrition program with stillbirth by race, ethnicity, and maternal characteristics

BACKGROUND

Participation in the Special Supplemental Nutrition Program for Women, Infants and Children (WIC) has been associated with lower risk of stillbirth. We hypothesized that such an association would differ by race/ethnicity because of factors associated with WIC participation that confound the association.

METHODS

We conducted a secondary analysis of the Stillbirth Collaborative Research Network's population-based case-control study of stillbirths and live-born controls, enrolled at delivery between March 2006 and September 2008. Weighting accounted for study design and differential consent. Five nested models using multivariable logistic regression examined whether the WIC participation/stillbirth associations were attenuated after sequential adjustment for sociodemographic, health, healthcare, socioeconomic, and behavioral factors. Models also included an interaction term for race/ethnicity x WIC.

RESULTS

In the final model, WIC participation was associated with lower adjusted odds (aOR) of stillbirth among non-Hispanic Black women (aOR: 0.34; 95% CI 0.16, 0.72) but not among non-Hispanic White (aOR: 1.69; 95% CI: 0.89, 3.20) or Hispanic women (aOR: 0.91; 95% CI 0.52, 1.52).

CONCLUSIONS

Contrary to our hypotheses, control for potential confounding factors did not explain disparate findings by race/ethnicity. Rather, WIC may be most beneficial to women with the greatest risk factors for stillbirth. WIC-eligible, higher-risk women who do not participate may be missing the potential health associated benefits afforded by WIC.

The fetuses-at-risk approach: survival analysis from a fetal perspective

Several phenomena in contemporary perinatology create challenges for analyzing pregnancy outcomes. These include recent increases in iatrogenic delivery at late preterm and early term gestation, which are incongruent with the belief that stillbirth and neonatal death risks decrease exponentially with advancing gestational age. Perinatal epidemiologists have also puzzled over the paradox of intersecting birthweight-specific and gestational age-specific perinatal mortality curves for decades. For example, neonatal mortality rates among preterm infants of women who smoke are substantially lower than neonatal mortality rates among preterm infants of non-smoking women, whereas the reverse pattern occurs at term gestation. This mortality crossover is observed across several contrasts (for example, women with hypertensive disorders of pregnancy vs. normotensive women, older vs. younger women, twins vs. singletons) and outcomes (stillbirth, neonatal death, sudden infant death syndrome and cerebral palsy), and irrespective of how advancing "maturity" is defined (birthweight or gestational age). One approach proposed to address and explain these unexpected phenomena is the fetuses-at-risk model. This formulation involves a reconceptualization of the denominator for perinatal outcome rates from births to surviving fetuses. In this overview of the fetuses-at-risk model, we discuss the central tenets of the births-based and the fetuses-based formulations. We also describe the extension of the fetuses-at-risk approach to outcomes into and beyond the neonatal period and to a multivariable adaptation. Finally, we provide a substantive context by discussing biological mechanisms underlying the fetuses-at-risk model and contemporary obstetric phenomena that are better understood from that model than from one based on births.