US term stillbirth rates and the 39-week rule: a cause for concern?

The impact of ACOG's 39-week rule on fetal death rates in the United States: A systematic review

OBJECTIVE

The "39-week rule," implemented in August 2009, strongly discouraged early term deliveries before 39 weeks without accepted ACOG delivery indications. In this study, we evaluated fetal death rates before and after the 39-week rule in the United States (US) by review of published series.

STUDY DESIGN

Systematic literature searches were performed in PubMed, Cochrane Central Register of Controlled Trials, Embase, Cumulative Index to Nursing and Allied Health Literature, Web of Science, and Scopus databases (January 2009-June 2023). Searches were focused on the 39-week rule and fetal death. Articles were excluded if they were non-English, included non-US population, or included multiple gestations. The articles were then exported to EndNote for reference management and uploaded to Rayyan for title and abstract screening by two independent reviewers. The study was prospectively registered in PROSPERO.

RESULTS

Of 833 articles identified after initial search, 6 peer-reviewed studies met the inclusion criteria. After combining the data from these studies, there were 8713 fetal deaths/7,294,911 total births (0.12 %) post-implementation of the 39-week rule, and 8523 fetal deaths/7,705,422 total births (0.11 %) pre-implementation. Compared to pre-implementation, the odds of fetal death after implementation of the 39-week rule were 1.08 (95 % CI 1.05-1.11).

CONCLUSIONS

Implementation of ACOG's 39-week rule resulted in an 8 % increased risk of fetal death compared to pre-implementation of the 39-week rule. This is alarming, but must be evaluated in the setting of decreased neonatal morbidity and mortality following the introduction of the 39-week rule.

Long-term Risk for Type 1 Diabetes and Obesity in Early Term Born Offspring: A Systematic Review and Meta-Analysis

CONTEXT

Prematurity increases the long-term risks for endocrine and metabolic morbidity of offspring, but there is uncertainty regarding the risks for early-term deliveries (370/7-386/7 weeks of gestation).

OBJECTIVE

We aim to evaluate whether early-term deliveries increase the long-term risk for type 1 diabetes and obesity of offspring up to the age of 18 years compared with full-term children. PubMed, Medline, and EMBASE were searched. Observational cohort studies addressing the association between early-term delivery and long-term risk for type 1 diabetes and obesity, were included. Two independent reviewers extracted data and assessed risk of bias. Pooled relative risks (RRs) and heterogeneity were determined. Publication bias was assessed by funnel plots with Egger's regression line and contours, and sensitivity analyses were performed.

RESULTS

Eleven studies were included following a screen of 7500 abstracts. All studies were scored as high quality according to the Newcastle-Ottawa Quality Assessment Scale. Early-term delivery was significantly associated with an increased risk for type 1 diabetes (RR 1.19, 1.13-1.25), while the association was weaker for overweight and obesity (RR 1.05, 0.97-1.12). It is challenging to determine whether the association between early-term births and long-term morbidity represents a cause and effect relationship or is attributable to confounders. Most of the included studies adjusted for at least some possible confounders.

CONCLUSION

Compared with full-term offspring, early-term delivery poses a modest risk for long-term pediatric type 1 diabetes. Our analysis supports that, whenever medically possible, elective delivery should be avoided before 39 completed weeks of gestation.

Preterm, early term, and post-term infants from Riyadh mother and baby multicenter cohort study: The cohort profile

Background

Birth before 37 or beyond 42 gestational weeks is associated with adverse neonatal and maternal outcomes. Studies investigating determinants and outcomes of these deliveries are scarce. The objective of this study was to determine the neonatal birth profile in relation to the gestational age at delivery and to evaluate its influence on the immediate maternal and neonatal outcomes.

Methods

This is a multicenter cohort study of 13,403 women conducted in three hospitals in Riyadh. Collected data included sociodemographic characteristics, obstetric history, and physical and laboratory measurements. Regression models were developed to estimate the adjusted odds ratio (OR) and confidence intervals (CI) to determine factors associated with preterm, early term, and post-term births and to evaluate common maternal and neonatal risks imposed by deliveries outside the full term.

Results

The incidence of preterm, early term, and post-term delivery was 8.4%, 29.8%, and 1.4%, respectively. Hypertensive events during pregnancy consistently increased the risk of all grades of preterm births, from more than 3-fold for late preterm (OR = 3.40, 95% CI = 2.21-5.23) to nearly 7-fold for extremely early preterm (OR = 7.11, 95% CI = 2.24-22.60). Early term was more likely to occur in older mothers (OR = 1.30, 95% CI = 1.13-1.49), grand multiparous (OR = 1.21, 95% CI = 1.06-1.38), pregestational diabetes (OR = 1.91, 95% CI = 1.49-2.44), and gestational diabetes women (OR = 1.18, 95% CI = 1.05-1.33). The risk of post-term birth was higher in primiparous. In preterm births, the adverse outcome of neonates having an APGAR score of <7 at 5 min and admission to neonatal intensive care units increased progressively as the gestational age decreased. Post-term births are 2-fold more likely to need induction of labor; meanwhile, preterm births were more likely to deliver by cesarean section.

Conclusion

This large cohort study was the first in Saudi Arabia to assess the delivery profile across a continuum of gestational age and the associated maternal and neonatal adverse outcomes of deliveries outside the full-term period. The study showed that the prevalence of preterm and post-term birth in Saudi Arabia is similar to the prevalence in other high-income countries. The immediate adverse pregnancy outcomes inversely increased with the decrease in gestational age at delivery. In addition, maternal age, hypertension, diabetes, and parity influenced the gestational age at delivery.

Changes in Delivery Timing for High-Risk Pregnancies in the United States

OBJECTIVE

This study was aimed to assess whether the "39-week" rule is being extended to high-risk pregnancies and if so whether this has led to changes in neonatal morbidity or stillbirth.

STUDY DESIGN

Birth certificate data between 2010 and 2014 from 23 states (55% of births in the United States) were used. Pregnancies were classified as high risk if they had any one of the following: maternal age greater than or equal to 40 years, prepregnancy body mass index (BMI) greater than or equal to 40 kg/m², chronic (prepregnancy) hypertension, or diabetes (pregestational or gestational). Delivery timing changes for all pregnancies at term (37 weeks or greater) were compared with changes in the high-risk population. Neonatal morbidities (neonatal intensive care unit [NICU] admission, need for assisted ventilation, 5-minute Apgar score, and macrosomia), maternal morbidities (intensive care unit [ICU] admission, cesarean delivery, operative vaginal delivery, chorioamnionitis, and severe perineal laceration), and stillbirth rates were compared across time periods. Multivariate logistic regression was used to analyze whether gestational age-specific morbidity changes were due to shifts in delivery timing.

RESULTS

For the overall population, there was a shift in delivery timing between 2010 and 2014, a 2.5% decrease in 38-week deliveries, and a 2.3% increase in 39-week deliveries (p < 0.01). This gestational age shift was identical in the high-risk population (2.7% decrease in 38-week deliveries and 2.9% increase in 39-week deliveries). For the high-risk population, NICU admission increased from 5.4 to 6.3% in 2014 (p < 0.01) and assisted ventilation rates declined from 3.8 to 2.9% (p < 0.01). These changes, however, were independent of changes in delivery timing. There was no increase in the rate of stillbirth (0.23% in 2010 and 0.23% in 2014; p = 0.50).

CONCLUSION

There was a significant shift in delivery timing for high-risk pregnancies in the United States between 2010 and 2014. This shift, however, did not result in statistically significant changes in either neonatal morbidity or stillbirth.

KEY POINTS

· From 2010 to 2014, term deliveries for high-risk pregnancies shifted towards 39 weeks.. · The shift towards 39 weeks in high-risk pregnancies was not accompanied by any improvement in neonatal morbidity.. · The shift towards 39 weeks in high-risk pregnancies did not result in an increase in the stillbirth rate..

Is a 'guideline-compliant' primary cesarean delivery associated with a modified risk for maternal and neonatal morbidity?: a clinical evaluation of the 2014 ACOG/SMFM obstetric care consensus statement

BACKGROUND

It is currently unknown whether primary CDs performed in compliance with the 2014 ACOG/SMFM Obstetric Care Consensus Statement guidelines ("guideline-compliant") are associated with a modified risk of maternal and neonatal morbidity, when compared to primary CDs performed outside the guidelines ("guideline-noncompliant"). Our primary objective was to determine if a guideline-compliant primary CD is associated with a modified risk for maternal or neonatal morbidity, when compared to guideline-noncompliant primary CD.

METHODS

A retrospective cohort study of all primary CDs at one tertiary referral center in the calendar year following publication of the Consensus Statement. Logistic regression was performed to calculate the risk of adverse maternal and neonatal outcomes for guideline-compliant primary CDs, when compared to guideline-noncompliant and guideline-not addressed, and when adjusted for maternal age, BMI, hypertension, gestational age at delivery, insurance carrier, and provider practice.

RESULTS

Eight hundred twenty-seven primary CDs were included during the study period, of which 34.8, 26.0, and 39.2% were guideline compliant, guideline-noncompliant, and guideline-not addressed. No statistically significant differences in the frequency of adverse maternal outcomes across these three groups were observed with the exception of maternal ICU admission, which was significantly associated with a guideline-not addressed primary CD (p = 0.0002). No statistical difference in rates of NICU admissions, 5 min APGAR < 5, or umbilical artery cord pH < 7 were observed between guideline-compliant and guideline-noncompliant primary CDs.

CONCLUSION

Women undergoing guideline-compliant primary CDs were not significantly more likely to experience a maternal or neonatal morbidity when compared to guideline-noncompliant primary CDs.

Australia's persistently high rate of early-term prelabour Caesarean delivery

Objective To compare the incidence of prelabour Caesarean delivery (PCD) at early term (37 weeks and 0 days (370) to 38 weeks and 6 days (386) of gestation) between Australian states and hospital sectors over time and to compare these rates with those of England and the United States of America (USA). Method A population-based descriptive study of 556040 singleton PCDs at term (370-406 weeks) in all public and private hospitals in Australian states, 2005-16, was performed. The primary outcome was the early-term PCD rate, defined as early-term PCDs as a percentage of all term PCDs. Results Across Australian states, the early-term PCD rate fell from 56.4% in 2005 to 52.0% in 2016. Over a similar period, England's rate fell from 48.2% in 2006-07 to 35.2% in 2016-17, while the USA's rate fell from 47.4% in 2006 to 34.2% in 2016. Australian public hospitals reduced their rate from 54.2% in 2005 to 44.7% in 2016, but the rate increased in private hospitals from 59.1% in 2005 to 62.5% in 2016. There was considerable variation between states and hospital sectors. Conclusions The early-term PCD rate increased in Australian private hospitals from 2005 to 2016. The public hospital rate fell by nearly 10% over the period but remained ~10% above the English and USA national rates. What is known about the topic? Babies born at early term (370-386 weeks) are at greater risk of morbidity than babies born at full term (390-406 weeks). Australia has a persistently high rate of early-term prelabour Caesarean delivery (PCD). What does this paper add? This paper reveals concerning differences in the early-term PCD rate between Australian states and hospital sectors. Further, the paper highlights that both Australian hospital sectors (public and private) have not reduced their rates to levels achieved in England and the USA. What are the implications for practitioners? These results should inform efforts to reduce Australia's early-term PCD rate to prevent harm to babies.

Risk Factors for Stillbirth among Pregnant Women Infected with Syphilis in the Zhejiang Province of China, 2010-2016

BACKGROUND

The World Health Organization estimated that about 1.36 million pregnant women suffered from syphilis in 2008, and nearly 66% of adverse effects occurred in those who were not tested or treated. Syphilis infection is one of the most common maternal factors associated with stillbirth.

OBJECTIVE

This study aimed to determine the risk factors for stillbirth among pregnant women infected with syphilis.

METHODS

In this retrospective study, data on stillbirth and gestational syphilis from 2010 to 2016 were extracted from the prevention of mother-to-child transmission (PMTCT) program database in the Zhejiang province. A total of 8,724 pregnant women infected with syphilis were included. Multiple logistic regression analysis was performed to determine the degree of association between gestational syphilis and stillbirth.

RESULTS

We found that the stillbirth percentage among pregnant women infected with syphilis was 1.7% (152/8,724). Compared with live births, stillbirth was significantly associated with lower maternal age, not being married, lower gravidity, the history of syphilis, nonlatent syphilis stage, higher maternal serum titer for syphilis, inadequate treatment for syphilis, and later first antenatal care visit. In multiple logistic analysis, nonlatent syphilis (adjusted odds ratio (AOR) = 2.03; 95% CI = 1.17, 3.53) and maternal titers over 1 : 4 (AOR = 1.78; 95% CI = 1.25, 2.53) were risk factors for stillbirth, and adequate treatment was the only protective factor for stillbirth (AOR = 0.16; 95% CI = 0.10, 0.25).

CONCLUSIONS

Nonlatent syphilis and maternal titers over 1 : 4 were risk factors for stillbirth, and adequate treatment was the only protective factor for stillbirth.

Evidence-based labor management: induction of labor (part 2)

Induction of labor is indicated for many obstetrical, maternal, and fetal indications. Induction can be offered for pregnancy at 39 weeks' gestation. No prediction method is considered sensitive or specific enough to determine the incidence of cesarean delivery after induction. A combination of 60- to 80-mL single-balloon Foley catheter for 12 hours and either 25-μg oral misoprostol initially, followed by 25 μg every 2-4 hours, or 50 μg every 4-6 hours (if no more than 3 contractions per 10 minutes or previous uterine surgery), or oxytocin infusion should be recommended for induction of labor. Adding membrane stripping at the beginning of induction should be considered. Once 5-6 cm of cervical dilation is achieved during the induction of labor, consideration can be given to discontinue oxytocin infusion if in use at that time and adequate contractions are present. Induction with oxytocin immediately (as soon as feasible) or up to 12 hours of term prelabor rupture of membranes if labor is not evident is recommended. Outpatient Foley ripening can be considered for low-risk women. Cesarean delivery should not be performed before 15 hours of oxytocin infusion and amniotomy if feasible and ideally after 18-24 hours of oxytocin infusion.

Association of Widespread Adoption of the 39-Week Rule With Overall Mortality Due to Stillbirth and Infant Death

IMPORTANCE

To improve neonatal morbidity, efforts have been made to reduce elective deliveries prior to 39 weeks' gestation, also known as the 39-week rule. Prolonging pregnancies also prolongs exposure to the risk of stillbirth. The true association of a 39-week rule with mortality is unknown and studies to date have shown conflicting results.

OBJECTIVE

To determine if widespread adoption of a 39-week rule, limiting elective deliveries prior to 39 weeks' gestation, is associated with an increase or decrease in overall mortality when considering both stillbirths and infant deaths.

DESIGN, SETTING, AND PARTICIPANTS

This historical cohort study used birth certificate and infant death certificate data in the United States to compare years before and after the adoption of the 39-week rule. Births between 2008 and 2009 were considered to be in the preadoption period (n = 7 322 234), and those between 2011 and 2012 were considered to be in the postadoption period (n = 6 972 626). Included births were singleton, nonanomalous births between 37 0/7 weeks' and 42 6/7 weeks' gestation. Statistical analysis was performed from July 19, 2016, through June 27, 2019.

EXPOSURES

The exposure of interest was the Joint Commission adoption of the 39-week rule as a quality measure.

MAIN OUTCOMES AND MEASURES

The primary outcomes of interest were stillbirth and infant death.

RESULTS

A total of 7 322 234 births (49.0% girls and 51.0% boys) were included in the preadoption period and 6 972 626 births (49.1% girls and 50.9% boys) were included in the postadoption period. Compared with the preadoption period, there was a decrease in the proportion of deliveries at 37 weeks (-0.06%) and 38 weeks (-2.5%) and an increase in the proportion of deliveries at 39 weeks (6.8%) and 40 weeks (0.2%) in the postadoption period (P < .001). The stillbirth rate increased in the postadoption cohort compared with preadoption (0.09% vs 0.10%; P < .001). The infant death rate decreased in the postadoption period compared with preadoption (0.21% vs 0.20%; P < .001). An overall mortality rate of 0.31% was calculated for the preadoption period and 0.30% for the postadoption period (P = .06). Additional analysis in a counterfactual model suggests that up to 34.2% of the difference in mortality could be associated with the 39-week rule.

CONCLUSIONS AND RELEVANCE

Stable overall perinatal mortality rates were observed in the 2-year period immediately after adoption of the 39-week rule, despite an increase in stillbirth.

ACOG Committee Opinion No. 765: Avoidance of Nonmedically Indicated Early-Term Deliveries and Associated Neonatal Morbidities

There are medical indications in pregnancy for which there is evidence or expert opinion to support delivery versus expectant management in the early-term period. However, the risk of adverse outcomes is greater for neonates delivered in the early-term period compared with neonates delivered at 39 weeks of gestation. In addition to immediate adverse perinatal outcomes, multiple studies have shown increased rates of adverse long-term infant outcomes associated with late-preterm and early-term delivery compared with full-term delivery. A recent systematic review found that late-preterm and early-term children have lower performance scores across a range of cognitive and educational measures compared with their full-term peers. Further research is needed to better understand if these differences are primarily based on gestational age at delivery versus medical indications for early delivery. Documentation of fetal pulmonary maturity alone does not necessarily indicate that other fetal physiologic processes are adequately developed. For this reason, amniocentesis for fetal lung maturity is not recommended to guide timing of delivery, even in suboptimally dated pregnancies. Avoidance of nonmedically indicated delivery before 39 0/7 weeks of gestation is distinct from, and should not result in, an increase in expectant management of patients with medical indications for delivery before 39 0/7 weeks of gestation. Management decisions, therefore, should balance the risks of pregnancy prolongation with the neonatal and infant risks associated with early-term delivery. Although there are specific indications for delivery before 39 weeks of gestation, a nonmedically indicated early-term delivery should be avoided. This document is being revised to reflect updated data on nonmedically indicated early-term deliveries.

Unexpected term NICU admissions: a marker of obstetrical care quality?

BACKGROUND

Unexpected admissions of term neonates to the neonatal intensive care unit and unexpected postnatal complications have been proposed as neonatal-focused quality metrics for intrapartum care. Previous studies have noted significant variation in overall hospital neonatal intensive care unit admission rates; however, little is known about the influence of obstetric practices on these rates or whether variation among unanticipated admissions in low-risk, term neonates can be attributed to systemic hospital practices.

OBJECTIVE

The objective of the study was to examine the relative effects of patient characteristics and intrapartum events on unexpected neonatal intensive care unit admissions and to quantify the between-hospital variation in neonatal intensive care unit admission rates among this group of neonates.

STUDY DESIGN

We performed a retrospective cross-sectional study using data collected as part of the Consortium for Safe Labor study. Women who delivered term (≥37 weeks), singleton, nonanomalous, liveborn infants without an a priori risk for neonatal intensive care unit admission were included. The primary outcome was neonatal intensive care unit admission among this population. Multilevel mixed-effect models were used to calculate adjusted odds ratios for demographics (age, race, insurer), pregnancy characteristics (parity, gestational age, tobacco use, birthweight), maternal comorbidities (chronic and pregnancy-induced hypertension), hospital characteristics (delivery volume, hospital and neonatal intensive care unit level, academic affiliation), and intrapartum events (prolonged second stage, induction of labor, trial of labor after cesarean delivery, chorioamnionitis, meconium-stained amniotic fluid, and abruption). Intraclass correlation coefficients were used to estimate the between-hospital variance in a series of hierarchical models.

RESULTS

Of the 143,951 infants meeting all patient and hospital inclusion criteria, 7995 (5.6%) were admitted to the neonatal intensive care unit after birth. In the fully adjusted model, the factors associated with the highest odds for neonatal intensive care unit admission included: nulliparity (adjusted odds ratio, 1.62 [95% confidence interval, 1.53-1.71]), large for gestational age (adjusted odds ratio, 1.59 [95% confidence interval, 1.47-1.71]), and small for gestational age (adjusted odds ratio, 1.60 [95% confidence interval, 1.47-1.73]). Induction of labor (adjusted odds ratio, 0.95 [95% confidence interval, 0.89-1.01]) was not associated with increased odds of neonatal intensive care unit admission compared with women who labored spontaneously. The events associated with higher odds of neonatal intensive care unit admission included: prolonged second stage (adjusted odds ratio, 1.66 [95% confidence interval, 1.51-1.83]); chorioamnionitis (adjusted odds ratio, 3.89 [95% confidence interval, 3.42-4.44]), meconium-stained amniotic fluid (adjusted odds ratio, 1.96 [95% confidence interval, 1.82-2.10]), and abruption (adjusted odds ratio, 2.64 [95% confidence interval, 2.16-.21]). Compared with women who did not labor, the odds of neonatal intensive care unit admission were lower for women who labored: adjusted odds ratio, 0.48 (95% confidence interval, 0.45-0.52) for women with no uterine scar and adjusted odds ratio, 0.83 (95% confidence interval, 0.73-0.94) for women with a uterine scar. There was significant variation in neonatal intensive care unit admission rates by hospital, ranging from 2.9% to 11.2%. After accounting for case mix and hospital characteristics, the between-hospital variance was 1.9%, suggesting that little of the variation was explained by the effect of the hospital.

CONCLUSION

This study contributes to the currently limited understanding of term, neonatal intensive care unit admission rates as a marker of obstetrical care quality. We demonstrated that significant variation exists in hospital unexpected neonatal intensive care unit admission rates and that certain intrapartum events are associated with an increased risk for neonatal intensive care unit admission after delivery. However, the between-hospital variation was low. Unmeasured confounders and extrinsic factors, such as neonatal intensive care unit bed availability, may limit the ability of unexpected term neonatal intensive care unit admissions to meaningfully reflect obstetrical care quality.

Elective Induction of Labor: What is the Impact?

Elective induction of labor (ie, without a maternal or fetal indication) is common in the United States. When using the correct comparison group (elective induction vs expectant management) induction is not associated with an increased risk of cesarean delivery. Moreover, elective induction after 39 weeks seems to have maternal benefits (eg, lower infection rates) as well as a reduction in neonatal morbidity and the potential for a decrease in term stillbirth. However, these risks, especially stillbirth, are low in a healthy cohort and there are potential negative impacts on maternal satisfaction, breastfeeding, and cost/resource use that must be considered.

Evidence that fetal death is associated with placental aging

BACKGROUND

The risk of unexplained fetal death or stillbirth increases late in pregnancy, suggesting that placental aging is an etiological factor. Aging is associated with oxidative damage to DNA, RNA, and lipids. We hypothesized that placentas at >41 completed weeks of gestation (late-term) would show changes consistent with aging that would also be present in placentas associated with stillbirths.

OBJECTIVE

We sought to determine whether placentas from late-term pregnancies and unexplained stillbirth show oxidative damage and other biochemical signs of aging. We also aimed to develop an in vitro term placental explant culture model to test the aging pathways.

STUDY DESIGN

We collected placentas from women at 37-39 weeks' gestation (early-term and term), late-term, and with unexplained stillbirth. We used immunohistochemistry to compare the 3 groups for: DNA/RNA oxidation (8-hydroxy-deoxyguanosine), lysosomal distribution (lysosome-associated membrane protein 2), lipid oxidation (4-hydroxynonenal), and autophagosome size (microtubule-associated proteins 1A/1B light chain 3B, LC3B). The expression of aldehyde oxidase 1 was measured by real-time polymerase chain reaction. Using a placental explant culture model, we tested the hypothesis that aldehyde oxidase 1 mediates oxidative damage to lipids in the placenta.

RESULTS

Placentas from late-term pregnancies show increased aldehyde oxidase 1 expression, oxidation of DNA/RNA and lipid, perinuclear location of lysosomes, and larger autophagosomes compared to placentas from women delivered at 37-39 weeks. Stillbirth-associated placentas showed similar changes in oxidation of DNA/RNA and lipid, lysosomal location, and autophagosome size to placentas from late-term. Placental explants from term deliveries cultured in serum-free medium also showed evidence of oxidation of lipid, perinuclear lysosomes, and larger autophagosomes, changes that were blocked by the G-protein-coupled estrogen receptor 1 agonist G1, while the oxidation of lipid was blocked by the aldehyde oxidase 1 inhibitor raloxifene.

CONCLUSION

Our data are consistent with a role for aldehyde oxidase 1 and G-protein-coupled estrogen receptor 1 in mediating aging of the placenta that may contribute to stillbirth. The placenta is a tractable model of aging in human tissue.

A mouse model of antepartum stillbirth

BACKGROUND

Many stillbirths of normally formed fetuses in the third trimester could be prevented via delivery if reliable means to anticipate this outcome existed. However, because the etiology of these stillbirths is often unexplained and although the underlying mechanism is presumed to be hypoxia from placental insufficiency, the placentas often appear normal on histopathological examination. Gestational age is a risk factor for antepartum stillbirth, with a rapid rise in stillbirth rates after 40 weeks' gestation. We speculate that a common mechanism may explain antepartum stillbirth in both the late-term and postterm periods. Mice also show increasing rates of stillbirth when pregnancy is artificially prolonged. The model therefore affords an opportunity to characterize events that precede stillbirth.

OBJECTIVE

The objective of the study was to prolong gestation in mice and monitor fetal and placental growth and cardiovascular changes.

STUDY DESIGN

From embryonic day 15.5 to embryonic day 18.5, pregnant CD-1 mice received daily progesterone injections to prolong pregnancy by an additional 24 hour period (to embryonic day 19.5). To characterize fetal and placental development, experimental assays were performed throughout late gestation (embryonic day 15.5 to embryonic day 19.5), including postnatal day 1 pups as controls. In addition to collecting fetal and placental weights, we monitored fetal blood flow using Doppler ultrasound and examined the fetoplacental arterial vascular geometry using microcomputed tomography. Evidence of hypoxic organ injury in the fetus was assessed using magnetic resonance imaging and pimonidazole immunohistochemistry.

RESULTS

At embryonic day 19.5, mean fetal weights were reduced by 14% compared with control postnatal day 1 pups. Ultrasound biomicroscopy showed that fetal heart rate and umbilical artery flow continued to increase at embryonic day 19.5. Despite this, the embryonic day 19.5 fetuses had significant pimonidazole staining in both brain and liver tissue, indicating fetal hypoxia. Placental weights at embryonic day 19.5 were 21% lower than at term (embryonic day 18.5). Microcomputed tomography showed no change in quantitative morphology of the fetoplacental arterial vasculature between embryonic day 18.5 and embryonic day 19.5.

CONCLUSION

Prolongation of pregnancy renders the murine fetus vulnerable to significant growth restriction and hypoxia because of differential loss of placental mass rather than any compromise in fetoplacental blood flow. Our data are consistent with a hypoxic mechanism of antepartum fetal death in human term and postterm pregnancy and validates the inability of umbilical artery Doppler to safely monitor such fetuses. New tests of placental function are needed to identify the late-term fetus at risk of hypoxia to intervene by delivery to avoid antepartum stillbirth.

Perinatal legislative policies and health outcomes

Perinatal epidemiology examines the variation and determinants of pregnancy outcomes from a maternal and neonatal perspective. However, improving public and population health also requires the translation of this evidence base into substantive public policies. Assessing the impact of such public policies requires sufficient data to include potential confounding factors in the analysis, such as coexisting medical conditions and socioeconomic status, and appropriate statistical and epidemiological techniques. This review will explore policies addressing three areas of perinatal medicine-elective deliveries prior to 39 weeks' gestation; perinatal regionalization; and mandatory paid maternity leave policies-to illustrate the challenges when assessing the impact of specific policies at the patient and population level. Data support the use of these policies to improve perinatal health, but with weaker and less certain effect sizes when compared to the initial patient-level studies. Improved data collection and epidemiological techniques will allow for improved assessment of these policies and the identification of potential areas of improvement when translating patient-level studies into public policies.

Variation in clinical decision-making for induction of labour: a qualitative study

Background

Unexplained variation in induction of labour (IOL) rates exist between hospitals, even after accounting for casemix and hospital differences. We aimed to explore factors that influence clinical decision-making for IOL that may be contributing to the variation in IOL rates between hospitals.

Methods

We undertook a qualitative study involving semi-structured, audio-recorded interviews with obstetricians and midwives. Using purposive sampling, participants known to have diverse opinions on IOL were selected from ten Australian maternity hospitals (based on differences in hospital IOL rate, size, location and case-mix complexities). Transcripts were indexed, coded, and analysed using the Framework Approach to identify main themes and subthemes.

Results

Forty-five participants were interviewed (21 midwives, 24 obstetric medical staff). Variations in decision-making for IOL were based on the obstetrician’s perception of medical risk in the pregnancy (influenced by the obstetrician’s personality and knowledge), their care relationship with the woman, how they involved the woman in decision-making, and resource availability. The role of a ‘gatekeeper’ in the procedural aspects of arranging an IOL also influenced decision-making. There was wide variation in the clinical decision-making practices of obstetricians and less accountability for decision-making in hospitals with a high IOL rate, with the converse occurring in hospitals with low IOL rates.

Conclusion

Improved communication, standardised risk assessment and accountability for IOL offer potential for reducing variation in hospital IOL rates.

Disparities in gestational age-specific fetal mortality rates in the United States, 2009-2013

PURPOSE

Although studies have examined overall temporal changes in gestational age-specific fetal mortality rates, there is little information on the current status of racial/ethnic differences. We hypothesize that differences exist between racial/ethnic groups across gestational age and that these differences are not equally distributed.

METHODS

Using the 2009-2013 data from US fetal death and live birth files for non-Hispanic white (NHW); non-Hispanic black (NHB); Hispanic; and American Indian/Alaska Native (AIAN) women, we conducted analyses to examine fetal mortality rates and estimate adjusted prevalence rate ratios and 95% confidence intervals (CIs).

RESULTS

There were lower risks of fetal mortality among NHB women (aPRR = 0.76; 95% CI = 0.71-0.81) and Hispanic women (aPRR = 0.89; 95% CI = 0.83-0.96) compared with NHWs at 22-23 weeks' gestation. For NHB women, the risk was higher starting at 32-33 weeks (aPRR = 1.11; 95% CI = 1.04-1.18) and continued to increase as gestational age increased. Hispanic and AIAN women had lower risks of fetal mortality compared with NHW women until 38-39 weeks.

CONCLUSIONS

Further examination is needed to identify causes of fetal death within the later pregnancy period and how those causes and their antecedents might differ by race and ethnicity.

Oregon's Hard-Stop Policy Limiting Elective Early-Term Deliveries: Association With Obstetric Procedure Use and Health Outcomes

OBJECTIVE

To evaluate the association of Oregon's hard-stop policy limiting early elective deliveries (before 39 weeks of gestation) and the rate of elective early-term inductions and cesarean deliveries and associated maternal-neonatal outcomes.

METHODS

This was a population-based retrospective cohort study of Oregon births between 2008 and 2013 using vital statistics data and multivariable logistic regression models. Our exposure was the Oregon hard-stop policy, defined as the time periods prepolicy (2008-2010) and postpolicy (2012-2013). We included all term or postterm, cephalic, nonanomalous, singleton deliveries (N=181,034 births). Our primary outcomes were induction of labor and cesarean delivery at 37 or 38 weeks of gestation without a documented indication on the birth certificate (ie, elective early term delivery). Secondary outcomes included neonatal intensive care unit admission, stillbirth, macrosomia, chorioamnionitis, and neonatal death.

RESULTS

The rate of elective inductions before 39 weeks of gestation declined from 4.0% in the prepolicy period to 2.5% during the postpolicy period (P<.001); a similar decline was observed for elective early-term cesarean deliveries (from 3.4% to 2.1%; P<.001). There was no change in neonatal intensive care unit admission, stillbirth, or assisted ventilation prepolicy and postpolicy, but chorioamnionitis did increase (from 1.2% to 2.2%, P<.001; adjusted odds ratio 1.94, 95% confidence interval 1.80-2.09).

CONCLUSIONS

Oregon's statewide policy to limit elective early-term delivery was associated with a reduction in elective early-term deliveries, but no improvement in maternal or neonatal outcomes.

Applying Precision Public Health to Prevent Preterm Birth

Preterm birth (PTB) is one of the major health-care challenges of our time. Being born too early is associated with major risks to the child with potential for serious consequences in terms of life-long disability and health-care costs. Discovering how to prevent PTB needs to be one of our greatest priorities. Recent advances have provided hope that a percentage of cases known to be related to risk factors may be amenable to prevention; but the majority of cases remain of unknown cause, and there is little chance of prevention. Applying the principle of precision public health may offer opportunities previously unavailable. Presented in this article are ideas that may improve our abilities in the fields of studying the effects of migration and of populations in transition, public health programs, tobacco control, routine measurement of length of the cervix in mid-pregnancy by ultrasound imaging, prevention of non-medically indicated late PTB, identification of pregnant women for whom treatment of vaginal infection may be of benefit, and screening by genetics and other “omics.” Opening new research in these fields, and viewing these clinical problems through a prism of precision public health, may produce benefits that will affect the lives of large numbers of people.

Outcomes of infants born near term

Most research on outcomes of preterm birth has centred on babies born at <32 weeks gestation and at highest risk of mortality and serious morbidity. Recent years have seen a dramatic increase in studies focusing on late preterm infants (34-36 weeks gestation). Early epidemiological studies demonstrated increased risks of mortality and adverse neonatal outcomes in this group, prompting further investigations. These increased risks have been confirmed and more recent studies have also included babies born at 37-38 weeks, now defined as 'early-term' births. It now seems that it is inappropriate to consider term and preterm as a dichotomy; gestational age rather represents a continuum in which risk and severity of adverse outcomes increase with decreasing gestational age, but where measurable effects can be detected even very close to full term. In this review, we summarise current evidence for the outcomes of infants born at late preterm and early-term gestations.