Risk for girls can be adversely affected post-term due to underestimation of gestational age by ultrasound in the second trimester

A cohort study of the occurrence of post-term births and its association with perinatal mortality in a rural area in Bangladesh

Background

We aimed to evaluate the trend of post-term births over time and their association with perinatal mortality based on prospective pregnancy cohorts in a rural area in Bangladesh.

Methods

This cohort study included 72 373 singleton births with gestational ages ≥28 weeks recorded by a health and demographic surveillance system from 1990 to 2019 in Matlab, Bangladesh. We expressed the gestational age as X (weeks) + Y (days)/7 weeks, where X indicated complete weeks, and Y presented the number of completed days out of seven days or a week. Using Poisson regression with robust variances, we estimated the population-based proportion of post-term births and assessed the association between gestational age categories and perinatal mortality. We presented results by adjusted relative risk (aRR) with 95% confidence intervals (CIs).

Results

Post-term births declined from 5.8% in 1990 to 2.8% in 2019. Perinatal mortality declined from 58 to 27 per 1000 births from 1990 to 2019. Compared to full-term births (39 + 0/7 to 40 + 6/7 weeks), the aRRs of perinatal mortality were 1.39 for late-term (41 + 0/7 to 41 + 6/7 weeks) and 1.93 for post-term (≥42 + 0/7 weeks) births. The population-attributable fraction of perinatal mortality was 15% for births at ≥41 + 0/7 weeks out of the total perinatal deaths occurring at ≥39 gestation weeks.

Conclusions

In this rural setting in Bangladesh, we observed a decline in post-term birth proportions from 1990 to 2019. We found increased perinatal mortality when pregnancy continued beyond 40 + 6/7 weeks of gestation. This implies that planning the management of pregnant women approaching the post-term period may be needed to further improve perinatal health outcomes.

Differing prevalence of microcephaly and macrocephaly in male and female fetuses

Objective

To compare the proportion of female and male fetuses classified as microcephalic (head circumference [HC] < 3rd percentile) and macrocephalic (>97th percentile) by commonly used sex-neutral growth curves.

Methods

For fetuses evaluated at a single center, we retrospectively determined the percentile of the first fetal HC measurement between 16 and 0/7 and 21-6/7 weeks using the Hadlock, Intergrowth-21st, and NICHD growth curves. The association between sex and the likelihood of being classified as microcephalic or macrocephalic was evaluated with logistic regression.

Results

Female fetuses (n = 3,006) were more likely than male fetuses (n = 3,186) to be classified as microcephalic using the Hadlock (0.4% male, 1.4% female; odds ratio female vs. male 3.7, 95% CI [1.9, 7.0], p < 0.001), Intergrowth-21st (0.5% male, 1.6% female; odds ratio female vs. male 3.4, 95% CI [1.9, 6.1], p < 0.001), and NICHD (0.3% male, 1.6% female; odds ratio female vs. male 5.6, 95% CI [2.7, 11.5], p < 0.001) curves. Male fetuses were more likely than female fetuses to be classified as macrocephalic using the Intergrowth-21st (6.0% male, 1.5% female; odds ratio male vs. female 4.3, 95% CI [3.1, 6.0], p < 0.001) and NICHD (4.7% male, 1.0% female; odds ratio male vs. female 5.1, 95% CI [3.4, 7.6], p < 0.001) curves. Very low proportions of fetuses were classified as macrocephalic using the Hadlock curves (0.2% male, < 0.1% female; odds ratio male vs. female 6.6, 95% CI [0.8, 52.6]).

Conclusion

Female fetuses were more likely to be classified as microcephalic, and male fetuses were more likely to be classified as macrocephalic. Sex-specific fetal head circumference growth curves could improve interpretation of fetal head circumference measurements, potentially decreasing over- and under-diagnosis of microcephaly and macrocephaly based on sex, therefore improving guidance for clinical decisions. Additionally, the overall prevalence of atypical head size varied using three growth curves, with the NICHD and Intergrowth-21st curves fitting our population better than the Hadlock curves. The choice of fetal head circumference growth curves may substantially impact clinical care.

Maternal and fetal characteristics affect discrepancies between pregnancy-dating methods: a population-based cross-sectional register study

INTRODUCTION

Gestational age is estimated by ultrasound using fetal size as a proxy for age, although variance in early growth affects reliability. The aim of this study was to identify characteristics associated with discrepancies between last menstrual period-based (EDD-LMP) and ultrasound-based (EDD-US) estimated delivery dates.

MATERIAL AND METHODS

We identified all singleton births (n = 1 201 679) recorded in the Swedish Medical Birth Register in 1995-2010, to assess the association between maternal/fetal characteristics and large negative and large positive discrepancies (EDD-LMP earlier than EDD-US and 10th percentile in the discrepancy distribution vs. EDD-LMP later than EDD-US and 90th percentile). Analyses were adjusted for age, parity, height, body mass index, smoking, and employment status.

RESULTS

Women with a body mass index >40 kg/m² had the highest odds for large negative discrepancies (-9 to -20 days) [odds ratio (OR) 2.16, 95% CI 2.01-2.33]. Other factors associated with large negative discrepancies were: diabetes, young maternal age, multiparity, body mass index between 30 and 39.9 kg/m² or <18.5 kg/m² , a history of gestational diabetes, female fetus, shorter stature (<-1 SD), a history of preeclampsia, smoking or snuff use, and unemployment. Large positive discrepancies (+4 to +20 days) were associated with male fetus (OR 1.80, 95% CI 1.77-1.83), age ≥30 years, multiparity, not living with a partner, taller stature (>+1 SD), and unemployment.

CONCLUSIONS

Several maternal and fetal characteristics were associated with discrepancies between dating methods. Systematic associations of discrepancies with maternal height, fetal sex, and partly obesity, may reflect an influence on the precision of the ultrasound estimate due to variance in early growth.