Prediction of intra-twin birth weight discordance by binary logistic regression analysis

The associations of birth outcome differences in twins with prenatal exposure to bisphenol A and its alternatives

BACKGROUND

Bisphenol A (BPA) and its alternatives, including BPF and BPS, exhibit endocrine disruption activities. However, the effects of bisphenols on fetal growth in twins remain unclear.

OBJECTIVE

To explore the associations of prenatal BPA, BPF, and BPS exposure with birth outcome differences in twins.

METHODS

We recruited 289 twin pregnant women who visited the hospital for prenatal examination during the first trimester from 2013 to 2016. Urinary bisphenol levels were determined during the first, second, and third trimesters. The associations of maternal exposure to bisphenols with birth outcome differences in twins were analyzed after stratification by different trimesters. We applied the multiple informant model to estimate trimester-specific associations between urinary bisphenol concentrations and birth outcome differences in twins.

RESULTS

We found low reproducibility (ICC<0.40) for maternal urinary BPA and moderate reproducibility (0.40 < ICC<0.75) for BPF and BPS. Urinary BPA concentrations were positively associated with within-pair twin birth weight difference when comparing the third vs. the first tertile in each of the three trimesters (i.e., 133.06 g, 95% CI: 68.19, 197.94; 144.5 g, 95%CI: 81.82-207.18 g; and 135.04 g, 95%CI: 71.37-198.71 g for the 1st, 2nd, and 3rd trimester, respectively). The effect of urinary BPA concentration on increased birth length difference within-pair twins were also observed across different trimesters (All P for trends < 0.05). Urinary BPA levels were positively associated with the within-pair birth weight and birth length differences across pregnancy trimesters (All of Type 3 P for values < 0.05).

CONCLUSION

Maternal BPA exposure appeared to influence birth wight and birth length differences in twins. Our results warrant further confirmation.

Twin growth discordance in association with maternal exposure to fine particulate matter and its chemical constituents during late pregnancy

BACKGROUND

Twin growth discordance is one of the leading causes of perinatal mortality in twin pregnancies. Whether prenatal exposure to fine particle (PM_2.5) air pollution is associated with twin growth discordance have not been studied yet.

OBJECTIVE

To evaluate the associations of prenatal exposure to PM_2.5 and its chemical constituents with twin growth discordance.

METHODS

This study included 1917 twin pairs and their mothers drawn from a previous twin birth cohort at the Shanghai First Maternity and Infant hospital in Shanghai, China. Exposure to PM_2.5 total mass and 6 key chemical constituents during the whole pregnancy and each trimester of pregnancy was represented by satellite-based models.

RESULTS

Maternal exposures to PM_2.5 total mass and chemical constituents of sulfate (SO₄^2-) and ammonium (NH₄⁺) during the third trimester were significantly associated with increased within-pair birth weight difference and intertwin birth weight discordance. The within-pair birth weight difference increased by 30.6 g (β = 30.6, 95% CI, 4.4-56.9), 19.2 g (β = 19.2, 95% CI, 0.2-38.1) and 33.2 g (β = 33.2, 95% CI, 7.9-58.6) for an IQR increase in PM_2.5 total mass, SO₄^2- and NH₄⁺ exposure, respectively. While the intertwin birth weight discordance increased by 1.3% (β = 1.3, 95% CI, 0.3-2.2), 0.9% (β = 0.9, 95% CI, 0.2-1.6) and 1.4% (β = 1.4, 95% CI, 0.4-2.3) for the same exposure metrics. Moreover, higher SO₄^2- and NH₄⁺ exposure was also associated with increased risk of twin growth discordance in linear dose-response manners. Compared to the lowest quartile of SO₄^2- (OR = 2.51, 95% CI, 1.08-5.82) and NH₄⁺ (OR = 2.97, 95% CI, 1.16-7.58) exposure, the odds of twin growth discordance were doubled in highest quartile of exposure.

CONCLUSION

Our results suggest that fine particle air pollution may be a risk factor for twin growth discordance. Late pregnancy seems to be a critical window for the effects of PM_2.5 exposure on fetal growth in twins.

The association between inter-twin birth weight discordance and hepatitis C: The United States 2011-2015 twin birth registration data

BACKGROUND

Twins with discordant growth have increased risks of perinatal mortality and morbidity. Previous studies have identified a number of risk factors for inter-twin birth weight discordance, yet no study has examined the effect of maternal hepatitis C infection.

METHODS

We used the twin birth records extracted from the 2011 to 2015 United States birth records created by the Centers for Disease Control and Prevention. The outcome variable of this study was inter-twin birth weight discordance, defined as [(birth weight of larger twin-birth weight of smaller twin) / birth weight of larger twin]. The independent association of hepatitis C infection with birth weight discordance was examined using the gamma regression or log binomial regression, adjusted by potential confounders.

RESULTS

Of the 270,256 twin pairs included in the final analysis, 850 (0.31%) had positive hepatitis C. Compared to mothers without hepatitis C, mothers with hepatitis C positive tended to have higher risk of birth weight discordance, but with no statistical significance. After adjustment for potential confounding factors, hepatitis C positive became a significant risk factor for birth weight discordance >25% (relative risk 1.14, 95% confidence interval 1.02-1.29). Sensitivity analyses (by treating birth weight discordance as a continuous outcome or dichotomizing into by different cutoffs) yielded similar results, with relative risks ranging from 1.07 to 1.12 (all P<0.05).

CONCLUSION

Maternal hepatitis C positive is associated with inter-twin birth weight discordance, an important adverse infant outcome in twin pregnancies, although the effect size is small.

Optimal threshold for birth weight discordance: Does knowledge of chorionicity matter?

OBJECTIVE

To establish the optimal threshold of birth weight discordance (BWD) for prediction of stillbirth, perinatal mortality and morbidity in twins born in British Columbia with or without chorionicity information.

STUDY DESIGN

This is a retrospective population-based cohort study of twins born in British Columbia from 2000 to 2010. Data from one hospital was used to adjust for chorionicity. Multivariate generalized estimating equation and receiver operating characteristic curve analyses were performed to evaluate the predictability of BWD in comparison with other fetal anthropometric measurements. Positive likelihood ratio is used to estimate test accuracy. Survival analysis was conducted to take gestational age and other confounders into account.

RESULTS

We analyzed two cohorts, with (pairs=1493) and without (pairs=6328) chorionicity information, of which 1.5% experienced stillbirth, 2.9% suffered perinatal mortality and 22.6% identified with perinatal morbidities. BWD was a significant predictor of stillbirth. Standard receiver operating characteristic curve analysis and survival analysis suggested that BWD of ⩾30% is the optimal thresholds for stillbirth and perinatal mortality irrespective of chorionicity. However, the P-value for predictive accuracy of BWD was nonsignificant for perinatal morbidity, after adjusting for confounding variables engaging multivariate analysis. Sex discordance can be used as a proxy for chorionicity.

CONCLUSION

BWD is a good predictor for stillbirth. A BWD cutoff limit of 30% and higher has optimal accuracy for detecting perinatal mortality.

Discordant twins: diagnosis, evaluation and management

Approximately 16% of twin gestations have discordance of at least 20%. We identified 14 risk factors for divergent growth that can be categorized as maternal, fetal, or placental. Determination of chorionicity and serial ultrasound evaluation with a high index of suspicion for divergent growth is required for the diagnosis and stratification of risk. The highest reported likelihood ratio for detection of discordance was 5.9 during the first trimester examination and 6.0 for the second trimester. Although our ability to identify discordant twins is limited, once suspected and at viable gestational age, these pregnancies should have antepartum testing. Discordant growth alone is not an indication for preterm birth. Although there are multiple publications on the increased morbidity and mortality rates with discordant growth, there is a paucity of reports on how to manage them optimally and deliver them in a timely manner.