Male-to-Female Ratios, Race/Ethnicity, and Spontaneous Preterm Birth among 11 Million California Infants

Were fewer boys born in the United States during the early months of the COVID-19 pandemic? A test of the Trivers-Willard hypothesis

The Trivers-Willard hypothesis predicts that mammalian parents in poor environmental conditions will favor the offspring sex with more reliable chance of reproductive success, which in humans is females. Three months following the onset of the COVID-19 pandemic in South Africa, England, and Wales, there were significant decreases in the sex ratio at birth (SRB) (male births/total live births). We analyzed this ratio with a seasonal autoregressive moving average model, and a logistic regression, using nationwide natality data for all singleton births in the United States from 2015 to 2021 (n = 25,201,620 total births). We identified no significant change in the sex ratio in either analysis. Rather, we observed marked differences in the sex ratio by maternal characteristics of race/ethnicity, age, and education, with more vulnerable groups having lower sex ratios. These findings suggest the SRB may be an important marker of reproductive vulnerability for disadvantaged groups in the United States.

Ambient Environment and the Epidemiology of Preterm Birth

Preterm birth (PTB) is associated with substantial mortality and morbidity. We describe environmental factors that may influence PTB risks. We focus on exposures associated with an individual's ambient environment, such as air pollutants, water contaminants, extreme heat, and proximities to point sources (oil/gas development or waste sites) and greenspace. These exposures may further vary by other PTB risk factors such as social constructs and stress. Future examinations of risks associated with ambient environment exposures would benefit from consideration toward multiple exposures - the exposome - and factors that modify risk including variations associated with the structural genome, epigenome, social stressors, and diet.

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.

Factors associated with infant sex and preterm birth status for selected birth defects from the National Birth Defects Prevention Study, 1997-2011

BACKGROUND

Birth defects and preterm birth co-occur, with some overlapping risk factors. Many birth defects and preterm births tend to have a male preponderance. We explored potential risk factors impacting sex and preterm (<37 weeks of gestation) birth differences among infants with selected birth defects delivered from 1997 to 2011 using data from the National Birth Defects Prevention Study (NBDPS).

METHODS

The NBDPS was a large multisite, population-based case-control study. Using random forests, we identified important predictors of male preterm, female preterm, and male term, each compared with female term births for each birth defect. Using logistic regression, we estimated odds ratios for associations between important predictors and sex-preterm birth status by birth defect.

RESULTS

We examined 11,379 infants with nine specific birth defects. The top 10 most important predictors of sex-preterm birth status from the random forests varied greatly across the birth defects and sex-preterm comparisons within a given defect group, with several being novel factors. However, one consistency was that short interpregnancy interval was associated with sex-preterm birth status for many of the studied birth defects. Although obesity has been identified as a risk factor for preterm birth and birth defects in other research, it was not associated with sex-preterm birth status for any of the examined defects.

CONCLUSIONS

We confirmed expected associations for sex-preterm birth status differences and found new potential risk factors for further exploration among the studied birth defects.

Survival of infants born at periviable gestation: The US national database

Background

Substantial differences exist in the approach to resuscitating infants born at periviable gestation. Evaluation of current survival may help guide prenatal counselling and provide accurate expectations of clinical outcomes. We aimed to assess the US national survival trends in periviable infants born at gestational age (GA) ≤24 weeks.

Methods

We used de-identified patient data obtained from the US Healthcare Cost and Utilization Project (HCUP) from 2007 to 2018. All infants with documented GA ≤24 weeks were included. The Cochran-Armitage test was used for trend analyses. Regression analyses were conducted for variables associated with survival.

Findings

A total of 44,628,827 infant records were identified with 124,345 (0.28%) infants born ≤24 weeks; of those, 77,050 infants <24 weeks and 47,295 infants had completed 24 weeks. Survival rates for infants <24 weeks and with completed 24 weeks were 15.4% and 71.6%, respectively, with higher survival over the years (Z = 9.438, P<0.001 & Z = 3.30, P<0.001, respectively). Survival was lower in males compared to females (aOR = 0.96, CI: 0.93-0.99 & aOR = 0.94, CI: 0.92-0.96, respectively) and with private insurance compared to public insurance (aOR = 0.74, CI: 0.71-0.77 & aOR = 0.67, CI: 0.65-0.69, respectively). Survival was higher when birth weight was >500 g compared to ≤500 g (aOR = 4.62, CI:3.23-5.02 & aOR = 5.44, CI: 4.59-5.84, respectively). Black (aOR = 1.33, CI: 1.31-1.36 & aOR = 1.24, CI: 1.20-1.32, respectively) and Hispanic (aOR = 1.29, CI: 1.27-1.32 & aOR = 1.27, CI: 1.22-1.30, respectively) had higher survival than White.

Interpretation

There is a national increase in survival over the years in infants born at periviable GA. BW >500 is associated with >4 folds higher survival compared to ≤500 g. The results of this study should be cautiously interpreted as long-term outcomes are unknown.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Diagnostic value of Serum Amyloid A, Interleukin-6 in gravidas with spontaneous preterm birth

PURPOSE

Spontaneous preterm birth (SPB) can't be predicted accurately nowadays. We aim to investigate the value of serum amyloid A(SAA) and interleukin-6(IL-6) for forecasting the risk of SPB.

METHODS

A total of 302 pregnant women who completed delivery in our hospital from January 2019 to December 2021 were included. According to gestational days, they were divided into the case group (28-33⁺⁶ weeks, 41 cases; 34-36⁺⁶ weeks, 96 cases) and the control group (37-42 weeks, 165 cases). The general data of the two groups were analyzed and the values of SAA and IL-6 in speculating the risk of SPB were studied in this study.

RESULTS

The levels of SAA and IL-6 in the case group were higher than those in the control group(P < 0.05), and the most practical value of SAA and IL-6 access SPB risk were 17.35 mg/L, 112.41 pg/mL respectively. The area under the ROC curve of diagnosis to predict SPB were 0.8849, 0.8664.

CONCLUSIONS

The assessment of SPB risk by SAA and IL-6 bearscertain clinical value, which could assist clinicians in recognizing and evaluating the potential dangers of SPB.

Ethnic differences in the impact of male fetal gender on the risk of spontaneous preterm birth

OBJECTIVE

To study the impact of fetal gender on the risk of spontaneous preterm birth in various ethnicities.

STUDY DESIGN

National cohort study in which all singleton live births from 25⁺⁰ weeks onwards without congenital anomalies were included of African, Asian, and Mediterranean women (1999-2010). Our primary outcome measure was preterm birth before 37 weeks. Per ethnic group, male and female neonates were compared.

RESULT

In each ethnic group, male fetuses were at increased risk of preterm birth (adjusted odds ratio (aOR) 1.63 for African, aOR 1.71 for Asian, and aOR 1.84 for Mediterranean males). The population-attributable risk of male gender on spontaneous preterm birth is lower in African women (3.9%) than in Asian (10.3%) and Mediterranean women (9.0%).

CONCLUSION

Male fetal gender is associated with spontaneous preterm birth in African, Asian, and Mediterranean women, but the total impact of ethnicity on spontaneous preterm birth rate is different.

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.

Preterm Birth in Assisted Reproductive Technology: An Analysis of More Than 20,000 Singleton Newborns

BACKGROUND

Several studies have shown that newborns conceived through the ART procedures were associated with an increased incidence of preterm delivery compared to those conceived spontaneously regardless of the type of ART procedure. The aim of the study was to explore risk factors for preterm birth (PTB) in assisted reproductive technology.

METHOD

In this single center retrospective cohort study, a total of 23,111 singleton newborns from January 2010 to December 2018 were included. The primary outcome in this study was preterm birth, defined as live birth before 37 weeks' gestation.

RESULT

In the 23,111 pregnancies, the incidence of PTB was 7.13%. In multivariate logistic regression analysis model, BMI was an independent predictor for PTB (OR = 1.05, 95% CI: 1.03-1.07; P = 0.00 in IVF/ICSI cycles; OR = 1.08, 95% CI: 1.03-1.12; P = 0.00 in IUI cycles). Also, another independent predictor in ART was male newborns (OR = 1.27, 95% CI: 1.14-1.41; P = 0.00 in IVF/ICSI cycles; OR = 1.60, 95% CI: 1.17-2.18; P = 0.00 in IUI cycles). In IVF/ICSI cycles, PTB was significantly higher in patients with advanced age (9.56% in ≥ 38 years old), and in patients with a history of cesarean section (10.39%). In addition, Blastocyst transfer, and frozen thawed transfer were also risk factor for PTB as compared with cleavage transfer, and fresh transfer, respectively. Moreover, in frozen thawed transfer cycles, stimulated protocol (estrogen-progesterone) increased PTB as compared with natural protocol (OR = 1.33, 95% CI: 1.12-1.59; P = 0.00). This situation was similar in IUI cycles as stimulated protocol also increased PTB when compared with natural protocol (OR = 1.72, 95% CI: 1.19-2.48; P = 0.00).

CONCLUSION

Body mass index (BMI), delivery with male newborn, as well as stimulated protocols, were independent risk factors for PTB in both IVF/ICSI and IUI treatment cycles. In IVF/ICSI cycles, independent risk factors also included maternal, history of cesarean section, frozen thawed transfer, and blastocyst transfer.