The China birth cohort study (CBCS) is a prospective longitudinal, mega-cohort study and the first national-based birth cohort study, aiming to establish a birth cohort covering representative geographical areas of the whole of China to investigate risk factors for birth defects and develop strategies for their reduction. Pregnant women who are of Chinese nationality, are 6–13⁺⁶ weeks of gestation, plan to attend the routine antenatal examination and deliver in the study site, and give their informed, written consent are eligible to participate in this study. All participants are followed-up through an in-person interview at 20–23⁺⁶ weeks and again at 28–33⁺⁶ weeks of gestation, and at delivery, respectively. CBCS has been divided into three phases from 20th November 2017 to 31st December 2021, and the first two phases have now been completed on 29th February 2020, enrolling 120 377 eligible pregnant women during this period. During the same period a total of 40 837 participants had been followed up to the end of pregnancy. Study recruitment will continue until December 2021 to achieve the target of 500 000 participants. Meanwhile, biological samples including peripheral blood, amniocytes, cord blood, placenta, or umbilical cord tissue have been collected from participants according to various conditions. The incidence of birth defects in this group is 2.5% and congenital heart disease is the most common type of birth defect seen so far. A website is in the advanced stages of planning, to allow seamless data transfer and facilitate collaboration with groups around the world.

Limited evidence exists regarding the association between ambient temperature and blood pressure (BP) level of pregnant women. To investigate the associations of ambient temperature with maternal BP and hypertensive disorders of pregnancy (HDP), we studied 105,063 participants in 38 centers of 17 provinces from November 2017 to December 2021. BP was measured with standardized automated digital sphygmomanometers. Ambient temperature was classified into five classes as very hot, moderate hot, mild, moderate cold, and very cold. Generalized linear mixed models were used to investigate the ambient temperature-BP/HDP associations, controlling for multiple covariates. No significant associations of first-trimester ambient temperature with maternal BP and HDP prevalence were observed. Compared with mild temperature, second-trimester very cold and second-trimester moderate cold were statistically associated with the increase of 1.239 mmHg (95% CI: 0.908, 1.569) and 0.428 mmHg (95% CI: 0.099, 0.757) for second-trimester systolic blood pressure (SBP), respectively. Similar trends were also observed in the association between second-trimester cold exposure and second-trimester diastolic blood pressure (DBP), in the association between second-trimester cold exposure and third-trimester SBP/DBP as well as in the association between third-trimester cold exposure and third-trimester SBP/DBP although some estimates were not statistically significant. Furthermore, in the second and third trimester, very cold [second trimester: adjusted odds ratio (aOR) = 1.298; third trimester: aOR = 1.236) and moderate cold (second trimester: aOR = 1.208; third trimester: aOR = 1.146) exposures also increased the odds of HDP, and these associations were stronger among participants aged ≥35 years or from North China. The second and third trimesters are the critical exposure windows for ambient temperature exposure-BP/HDP associations. During this period, exposure to cold ambient temperature was associated with elevated BP as well as increased HDP prevalence among most Chinese pregnant women, those aged ≥35 years or from North China being more vulnerable.

Context Previous studies on the relationship between thyroid gland function and the development of gestational diabetes mellitus (GDM) have reported different results, leading to the need for a cohort study design with a large sample size. Objective We aimed to investigate the relationship between thyroid function in early pregnancy and GDM. Methods This was a prospective cohort study based on the China Birth Cohort Study (CBCS), from February 2018 to December 2020. The study took place at a tertiary maternal and child health hospital. A total of 36 256 pregnant women were successfully recruited based on the CBCS. The main outcome measure was GDM. Results This study consisted of 26 742 pregnant women who met the inclusion criteria, of whom 3985 (14.90%) were diagnosed with GDM, and the women with GDM were older than their healthy counterparts (33.26 ± 4.01 vs 31.51 ± 3.76 years, P < .001). After removing potential influencing variables, we found that increased thyroid-stimulating hormone (TSH) (adjusted odds ratio [aOR] 1.030, 95% CI 1.007, 1.054, P = .012) and subclinical hypothyroidism (aOR 1.211, 95% CI 1.010, 1.451, P = .039), but not free thyroxine or thyroid peroxidase antibody, were associated with the occurrence of GDM. Further analysis indicated a nonlinear relationship between TSH and GDM (P < .05): when TSH ≤ 1.24 mIU/L, the occurrence of GDM was elevated with increasing TSH, but when TSH > 1.24 mIU/L, this trend was not obvious. Conclusion High TSH might be associated with increased risk of GDM.

Objective: Acute pancreatitis in pregnancy (APIP) is a rare and serious complication during pregnancy. It has acute onset and is difficult to diagnose and treat. The aim of the present study was to describe the etiology, clinical manifestations, and maternofetal outcomes of APIP. Methods: We retrospectively reviewed 32 pregnant women who were treated at three tertiary care hospitals in Beijing, China. The correlation between the causes of APIP, severity, laboratory indices, and outcomes was analyzed. Results: The most common causes of APIP were hypertriglyceridemia (56.2%,18/32) and gallstones (28.1%, 9/32). Hypertriglyceridemia-induced APIP was associated with a higher rate of severe acute pancreatitis (P = 0.025). Serum level of triglycerides showed a positive correlation with the severity of APIP (P = 0.039). The most frequent presentation of APIP was abdominal pain (93.7%, 30/32). There were no maternal or fetal deaths in our study. Apgar scores at 1 min, 5 min, and 10 min of the premature neonates was correlated with the severity of APIP of the mother (P = 0.022; 0.002; 0.002). Conclusion: High level of triglycerides may serve as a useful marker of the severity of APIP. The severity of APIP was associated with higher risk of neonate asphyxia. Appropriate timing of termination of pregnancy is a key imperative for APIP patients.

Gestational diabetes mellitus (GDM) is a common complication of pregnancy, which has significant adverse effects on both the mother and fetus. The incidence of GDM is increasing globally, and early diagnosis is critical for timely treatment and reducing the risk of poor pregnancy outcomes. GDM is usually diagnosed and detected after 24 weeks of gestation, while complications due to GDM can occur much earlier. Copy number variations (CNVs) can be a possible biomarker for GDM diagnosis and screening in the early gestation stage. In this study, we proposed a machine-learning method to screen GDM in the early stage of gestation using cell-free DNA (cfDNA) sequencing data from maternal plasma. Five thousand and eighty-five patients from north regions of Mainland China, including 1942 GDM, were recruited. A non-overlapping sliding window method was applied for CNV coverage screening on low-coverage (~0.2×) sequencing data. The CNV coverage was fed to a convolutional neural network with attention architecture for the binary classification. The model achieved a classification accuracy of 88.14%, precision of 84.07%, recall of 93.04%, F1-score of 88.33% and AUC of 96.49%. The model identified 2190 genes associated with GDM, including DEFA1, DEFA3 and DEFB1. The enriched gene ontology (GO) terms and KEGG pathways showed that many identified genes are associated with diabetes-related pathways. Our study demonstrates the feasibility of using cfDNA sequencing data and machine-learning methods for early diagnosis of GDM, which may aid in early intervention and prevention of adverse pregnancy outcomes.

Background: Spontaneous abortion is one of the prevalent adverse reproductive outcomes, which seriously threatens maternal health around the world.Objective: The current study is aimed to evaluate the association between maternal age and risk for spontaneous abortion among pregnant women in China.Methods: This was a case-control study based on the China Birth Cohort, we compared 338 cases ending in spontaneous abortion with 1,352 controls resulting in normal live births. The main exposure indicator and outcome indicator were maternal age and spontaneous abortion, respectively. We used both a generalized additive model and a two-piece-wise linear model to determine the association. We further performed stratified analyses to test the robustness of the association between maternal age and spontaneous abortion in different subgroups.Results: We observed a J-shaped relationship between maternal age and spontaneous abortion risk, after adjusting for multiple covariates. Further, we found that the optimal threshold age was 29.68 years old. The adjusted odds ratio (95% confidence interval) of spontaneous abortion per 1 year increase in maternal age were 0.97 (0.90–1.06) on the left side of the turning point and 1.25 (1.28–1.31) on the right side. Additionally, none of the covariates studied modified the association between maternal age and spontaneous abortion (P > 0.05).Conclusions: Advanced maternal age (>30 years old) was significantly associated with increased prevalence of spontaneous abortion, supporting a J-shaped association between maternal age and spontaneous abortion.