Impact of maternal thyroid hormone in late pregnancy on adverse birth outcomes: A retrospective cohort study in China

Spatial-temporal distribution of preterm birth in China, 1990-2020: A systematic review and modelling analysis

BACKGROUND

Little is known about the long-term trends of preterm birth rates in China and their geographic variation by province.

OBJECTIVES

To estimate the annual spatial-temporal distribution of preterm birth rates in China by province from 1990 to 2020.

DATA SOURCES

We searched PubMed, EMBASE, Web of Science, CNKI, WANFANG and VIP from January 1990 to September 2023.

STUDY SELECTION AND DATA EXTRACTION

Studies that provided data on preterm births in China after 1990 were included. Data were extracted following the Guidelines for Accurate and Transparent Health Estimates Reporting.

SYNTHESIS

We assessed the quality of each survey using a 9-point checklist. We estimated the annual preterm birth risk by province using Bayesian multilevel logistic regression models considering potential socioeconomic, environmental, and sanitary predictors.

RESULTS

Based on 634 survey data from 343 included studies, we found a gradual increase in the preterm birth risk in most provinces in China since 1990, with an average annual increase of 0.7% nationally. However, the preterm birth rates in Inner Mongolia, Hubei, and Fujian Province showed a decline, while those in Sichuan were quite stable since 1990. In 2020, the estimates of preterm birth rates ranged from 2.9% (95% Bayesian credible interval [BCI] 2.1, 3.8) in Inner Mongolia to 8.5% (95% BCI 6.6, 10.9) in Jiangxi, with the national estimate of 5.9% (95% BCI 4.3, 8.1). Specifically, some provinces were identified as high-risk provinces for either consistently high preterm birth rates (e.g. Jiangxi) or relatively large increases (e.g. Shanxi) since 1990.

CONCLUSIONS

This study provides annual information on the preterm birth risk in China since 1990 and identifies high-risk provinces to assist in targeted control and intervention for this health issue.

Prediction of preterm delivery based on thyroid peroxidase antibody levels and other identified risk factors

OBJECTIVE

Thyroid dysfunction and TPOAb positivity during pregnancy are associated with adverse pregnancy outcomes such as preterm delivery. The aim of this study was to predict preterm delivery based on identified risk factors, especially TPOAb levels.

STUDY DESIGN

A secondary analysis was run on data collected in the Tehran Thyroid and Pregnancy study (TTPs). We used the data of 1515 pregnant women with singletons. The association between risk factors and preterm birth (delivery before 37 completed weeks of gestation) was investigated in univariate analysis. Multivariate logistic regression analysis was performed to identify independent risk factors, and a stepwise backward elimination method was used to determine the helpful combination of risk factors. The nomogram was developed based on a multivariate logistic regression model. The performance of the nomogram was evaluated using a concordance index and calibration plots with bootstrap samples. Statistical analysis was performed using STATA software package; the significance level was set at P < 0.05.

RESULTS

Based on multivariate logistic regression analysis, a combination of previous preterm delivery [OR: 5.25; 95 %CI: (2.13-12.90), p < 0.01], TPOAb [OR: 1.01; 95 %CI: (1.01-1.02), and T4 [OR: 0.90; 95 %CI: (0.83-0.97); p = 0.04] as independent risk factors that most precisely predicted preterm birth. The area under the curve (AUC) was 0.66 (95% CI: 0.61-0.72). The calibration plot suggests that the fit of the nomogram is reasonable.

CONCLUSION

A combination of T4, TPOAb, and previous preterm delivery was identified as independent risk factors that accurately predicted preterm delivery. The total score obtained based on the nomogram designed based on risk factors can predict the risk of preterm delivery.

Associations of bisphenol exposure with thyroid hormones in pregnant women: a prospective birth cohort study in China

Bisphenols are endocrine disruptor chemicals that disrupt thyroid hormone homeostasis. However, evidence on the effects of bisphenol mixtures on thyroid hormones are insufficient. Therefore, the present study aimed to explore the effects of bisphenol substitutes and bisphenol mixtures on thyroid hormones during pregnancy. The study was conducted among 446 pregnant women in the Guangxi Zhuang Birth Cohort (GZBC), China. In multiple linear regressions, compared with the low-exposure group, bisphenol S (BPS) concentrations in the middle-exposure group led to a 10.90% (95% CI: - 18.16%, - 2.99%) decrease in triiodothyronine (T3) levels in the first trimester; tetrabromobisphenol A (TBBPA) levels in the middle-exposure group led to an 8.26% (95% CI: - 15.82%, - 0.01%) decrease in T3 levels in the first trimester; bisphenol B (BPB) levels in the middle-exposure group led to higher free thyroxine (FT4) levels (9.84%; 95% CI: 1.73%, 18.60%) in the second trimester; bisphenol F (BPF) in the middle-exposure group led to higher FT4 levels (8.59%, 95% CI: 0.53%, 17.31%) in the second trimester; and TBBPA levels in the high-exposure group led to a 9.39% (95% CI: 1.46%, 17.93%) increase in FT4 levels in the second trimester. The Bayesian kernel machine regression (BKMR) and restricted cubic spline (RCS) models showed a U-shaped dose-response relationship between bisphenol A (BPA) and free triiodothyronine (FT3) (p < 0.01) as well as BPS and FT4 (p < 0.05). Nonlinear relationships were also observed between the bisphenol mixture and FT3. Overall, maternal bisphenol exposure affected thyroid hormone levels during pregnancy. This study provides evidence that BPB, BPF, BPS, and TBBPA are unsafe substitutes for BPA, as well as the overall effect of bisphenols on adverse health in human beings.

Effect of vitamin A on the relationship between maternal thyroid hormones in early pregnancy and fetal growth: A prospective cohort study

Background

Fetal growth patterns are influenced by maternal thyroid function and vitamin A level during pregnancy. Vitamin A presents interactions with thyroid tissues and hormonal systems. We examined whether vitamin A status modified the associations of maternal thyroid hormones in early pregnancy and fetal growth outcomes among euthyroid pregnant women in a prospective cohort study (n = 637).

Methods

We performed multiple linear regression and multinomial logistic regression analysis to investigate the effects of thyroid hormones in early pregnancy on fetal growth according to different levels of serum vitamin A based on median value.

Results

A 1 pmol/L increase in maternal free triiodothyronine (FT3) levels was associated with an increased birth weight of 0.080 kg (p = 0.023) in women with lower maternal vitamin A levels in early pregnancy. Increased maternal free thyroxine (FT4) was associated with decreased odds for both small size for gestational age (SGA) [odds ratios (OR) = 0.66, 95% confidence interval (CI): 0.45–0.95] and large size for gestational age (LGA) (OR = 0.66, 95% CI: 0.45–0.98) in women with higher vitamin A level in early pregnancy after adjustment for maternal prepregnancy body mass index, gestational weight gain, maternal employed, parity, gestational week at sampling, and gestational diabetes mellitus.

Conclusions

In Chinese pregnant women without overt thyroid dysfunction, maternal FT4 in early pregnancy was positively associated with optimal fetal growth among women with higher serum vitamin A concentrations.

Low Fetal Fraction of Cell Free DNA at Non-Invasive Prenatal Screening Increases the Subsequent Risk of Preterm Birth in Uncomplicated Singleton Pregnancy

Objective

To examine the association between low fetal fraction (FF) of cell free DNA determined at non-invasive prenatal screening (NIPS) and the subsequent risk of preterm birth in uncomplicated singleton pregnancy.

Methods

We retrospectively interrogated NIPS System and hospitalization records from April 2018 to August 2019 and obtained results from 1521 consecutive and uncomplicated women with singleton pregnancy in which plasma FF of cell free DNA at NIPS had been investigated together with birth outcomes. We examined the association between FF and preterm birth (PTB) by regression analysis.

Results

The incidence of preterm birth, low birthweight, and macrosomia in the study population was 5.06%, 2.89%, and 7.17%, respectively. FF at NIPS in the second to fourth quartiles (8.40-11.07, 11.08-13.70, and >13.70%, respectively) was associated with higher gestational age at delivery relative to the lowest quartile (<8.40%), with estimated mean increases of 0.27 weeks (95% CI: 0.05-0.49), 0.29 weeks (95% CI: 0.06-0.51), and 0.28 weeks (95% CI: 0.05-0.51), respectively (P for trend = 0.027). Low FF (< the 5^th percentile) was associated with an increased risk of PTB (adjusted OR: 2.23, 95% CI: 1.01-4.98, P = 0.047) compared to normal FF (≥ the 5^th and ≤ the 95^th percentiles). In addition, when compared to women with normal FF and body mass index (BMI) <25 at NIPS, the risk of early PTB (< 34 weeks gestation) was remarkably significantly higher among those with low FF and BMI ≥25 (adjusted OR: 6.29, 95% CI: 1.71-23.15, P = 0.006).

Conclusion

Our study supports the association of low FF at NIPS with PTB (especially early PTB) for uncomplicated singleton pregnancy.

Bayes Conditional Probability-Based Causation Analysis between Gestational Diabetes Mellitus (GDM) and Pregnancy-Induced Hypertension (PIH): A Statistic Case Study in Harbin, China

Both gestational diabetes mellitus (GDM) and pregnancy-induced hypertension (PIH) would influence the gestation significantly. However, the causation between these two symptoms remains speculative. 16,404 pregnant women were identified in Harbin, China, in this study. We investigated and evaluated the causal effect of GDM on PIH based on the Bayes conditional probability. The statistical results indicated that PIH might cause GDM, but not vice versa. Also, this case study demonstrated that the decrease temperature might also cause hypertension during pregnancy, and the prevalence rate of GDM increased with age. However, the prevalence of diabetes did not show a remarkable difference in varied areas and ages. This study could provide some essential information that will help to investigate the mechanism for GDM and PIH.