Stillbirth and Infant Mortality Among Hispanic Singletons, Twins, and Triplets in the United States

Intertwin birthweight discordance and parental race: a retrospective cohort study

Objectives: Previous studies examined the association of maternal race with pregnancy outcomes. The study aimed to examine the effects of maternal, paternal, and parental race on intertwin birth weight discordance.Methods: We used the 2011-2015 multiple birth files of the USA for this study. The exposure variable of this study was parental race and intertwin birthweight discordance >25% was the outcome. In addition to separately analyzing maternal and paternal races, we assessed the effect of the combined race after grouping the participants into nine groups based on the race of both parents.Results: A total of 203,872 pairs of twins were included in the final analysis. The overall incidence of intertwin birthweight discordance in this population was 7.8%. Birthweight discordance was significantly associated with maternal, paternal, and parental races. Twins born to Black parents had significant risks of developing birthweight discordance than twins born to White parents (adjusted OR = 1.11, 95% CI: 1.06-1.17 for Black mothers and Black fathers). Combined parental race showed that compared to twins born to both parents Whites, twins born to both parents Blacks had a significantly elevated risk of developing birthweight discordance (adjusted OR = 1.13, 95% CI: 1.07-1.18). No significant difference in the risk of developing birthweight discordance was found for other parental race groups, same race or different race parents.Conclusions: Twins born to Black mothers, fathers, or both parents had significant risks of developing intertwin birthweight discordance than twins born to White mothers, fathers, or both parents.

Socioeconomic position, health behaviors, and racial disparities in cause-specific infant mortality in Michigan, USA

OBJECTIVES

Studies about racial disparities in infant mortality suggest that racial differences in socioeconomic position (SEP) and maternal risk behaviors explain some, but not all, excess infant mortality among Blacks relative to non-Hispanic Whites. We examined the contribution of these to disparities in specific causes of infant mortality.

METHODS

We analyzed data about 2,087,191 mother-child dyads in Michigan between 1989 and 2005. First, we calculated crude Black-White infant mortality ratios independently and by specific cause of death. Second, we fit multivariable Poisson regression models of infant mortality, overall and by cause, adjusting for SEP and maternal risk behaviors. Third, Crude Black-White mortality ratios were compared to adjusted predicted probability ratios, overall and by specific cause.

RESULTS

SEP and maternal risk behaviors explained nearly a third of the disparity in infant mortality overall, and over 25% of disparities in several specific causes including homicide, accident, sudden infant death syndrome, and respiratory distress syndrome. However, SEP and maternal risk behaviors had little influence on disparities in other specific causes, such as septicemia and congenital anomalies.

CONCLUSIONS

These findings help focus policy attention toward disparities in those specific causes of infant mortality most amenable to social and behavioral intervention, as well as research attention to disparities in specific causes unexplained by SEP and behavioral differences.

Life satisfaction and obstetric outcomes in the United States

OBJECTIVE

To examine the relation between life satisfaction and obstetric outcomes in the United States.

METHODS

Based on the Behavioral Risk Factor Surveillance System life satisfaction results (2005-2008), the 50 states and Washington, DC were categorized into higher, middle, and lower life satisfaction groups. We obtained data from the Centers for Disease Control and Prevention National Vital Statistics System (2005-2008) and calculated the fertility rates and fetal, neonatal, and infant mortality rates for the 50 states and Washington, DC. Correlations were examined. Risk ratios and 95% confidence intervals between groups were calculated.

RESULTS

There was a significant correlation between life satisfaction and fertility rate (r = 0.34; P = 0.012) and infant mortality rate (r = 0.28; P = 0.044). The higher group had a greater fertility rate, but it also had higher infant and neonatal mortality rates than those of the lower group.

CONCLUSIONS

Although the states with the most life satisfaction had higher fertility rates, they also had worse mortality outcomes. Birth outcomes may be more greatly affected by factors other than life satisfaction.

Second-trimester estimated fetal weight and discordance in twin pregnancies: association with fetal growth restriction

OBJECTIVES

The purpose of this study was to estimate the association between second-trimester estimated fetal weight and fetal growth restriction in twin pregnancies.

METHODS

A historical cohort of 306 twin pregnancies from a single center was analyzed. Estimated fetal weight and discordance at 18 to 24 weeks were calculated. Patients with a fetus whose second-trimester estimated fetal weight was below the 10th percentile were compared to patients with both fetuses at or above the 10th percentile. Also, patients with second-trimester discordance of 15% or greater were compared to patients with discordance of less than 15%.

RESULTS

Second-trimester discordance was significantly smaller than birth weight discordance (mean discordance ± SD, 7.41% ± 6.06% versus 11.43% ± 9.6%, respectively; P < .001). Patients with second-trimester discordance of 15% or greater were significantly more likely to deliver a twin with a birth weight below the 10th percentile for gestational age (67.7% versus 44.1%; P = .012) and below the 5th percentile for gestational age (41.9% versus 22.8%; P = .019). Patients with a second-trimester estimated fetal weight below the 10th percentile were significantly more likely to deliver a twin with a birth weight below the 10th percentile for gestational age (65.5% versus 44.5%; P = .031) and below the 5th percentile for gestational age (55.2% versus 21.5%; P < .001).

CONCLUSIONS

In twin pregnancies, second-trimester estimated fetal weight below the 10th percentile and discordance of 15% or greater are associated with fetal growth restriction.

U.S. Maternally linked birth records may be biased for Hispanics and other population groups

PURPOSE

We sought to advance understanding of linkage error in U.S. maternally linked datasets and how the error might affect results of studies based on the linked data.

METHODS

North Carolina birth and fetal death records for 1988-1997 were maternally linked (n=1,030,029). The maternal set probability, defined as the probability that all records assigned to the same maternal set do in fact represent events to the same woman, was used to assess differential maternal linkage error across race/ethnic groups.

RESULTS

Maternal set probabilities were lower for records specifying Asian or Hispanic race/ethnicity, suggesting greater maternal linkage error for these sets. The lower probabilities for Hispanics were concentrated in women of Mexican origin who were not born in the United States.

CONCLUSIONS

Differential linkage error may be a source of bias in studies that use U.S. maternally linked datasets to make comparisons between Hispanics and other groups or among Hispanic subgroups. Methods to quantify and adjust for this potential bias are needed.

Racial disparities in stillbirth risk across gestation in the United States

OBJECTIVE

We sought to determine factors associated with racial disparities in stillbirth risk.

STUDY DESIGN

Stillbirth hazard was analyzed using 5,138,122 singleton gestations from the National Center of Health Statistics perinatal mortality and birth files, 2001-2002.

RESULTS

Black women have a 2.2-fold increased risk of stillbirth compared with white women. The black/white disparity in stillbirth hazard at 20-23 weeks is 2.75, decreasing to 1.57 at 39-40 weeks. Higher education reduced the hazard for whites more than for blacks and Hispanics. Medical, pregnancy, and labor complications accounted for 30% of the hazard in blacks and 20% in whites and Hispanics. Congenital anomalies and small for gestational age contributed more to preterm stillbirth risk among whites than blacks. Pregnancy and labor conditions contributed more to preterm stillbirth risk among blacks than whites.

CONCLUSION

The excess stillbirth risk for blacks was greatest at preterm gestations, and factors contributing to stillbirth risk vary by race and gestational age.

Fetal growth and neonatal mortality in Korea

The fetal growth curve and neonatal mortality rate, based on gestational age and birthweight, are important for identifying groups of high-risk neonates and developing appropriate medical services and health-care programmes. The purpose of this study was to develop a national fetal growth curve for neonates in Korea, and examine the Korean national references for fetal growth and death according to their characteristics. Data of Korean vital statistics linked National Infant Mortality Survey conducted on births in 1999 were used in this study. The total livebirths were 621,764 in 1999, which were grouped into singletons (n = 609,643) and twins (n = 9805) for analysis. Birthweight/gestational age-specific fetal growth curves and neonatal mortality rates were based on 250 g of birthweight and weekly gestational age intervals for each characteristic of the birth. The features of high-risk neonates such as small-for-gestational-age and the limit of viability in Korea were different from those of Western countries. Difference in fetal growth and death was also detected in other characteristics of the fetus (gender and plurality of birth) besides race. The fetal growth curve of males was higher than that of females, and was higher in singleton than in twins. The neonatal mortality rate was higher in males (singleton, 2.6; twin, 23.5) than females (singleton, 2.1; twin, 15.9), and higher in twins (19.8/1000) than in singletons (2.4/1000). However, in neonates with gestational age >29 weeks and birthweight >1000 g, the neonatal mortality rate was lower in twins than in singletons. The limit of viability was gestational age 27 weeks and birthweight 1000 g, which was similar in singletons and twins regardless of gender. To improve the health of neonates in a country, it is imperative to investigate the characteristics of fetal growth and death under the particular circumstances of the country. When risk is defined for neonates account must be taken of differences in race, gender and plurality of birth, as the neonatal mortality rate varies depending on those factors.