The Xi'an longitudinal mother-child cohort study: design, study population and methods

Maximising the potential of Chinese birth cohort studies: a systematic review of mother-baby cohorts in mainland China

OBJECTIVES

There is now a growing interest in early-life influences on adult diseases in China. A number of birth cohorts have been established. This systematic review provided a better understanding of the development of mother-baby cohorts in China.

STUDY DESIGN

Systematic review.

METHODS

We conducted a systematic review for research or profile papers in English/Chinese that reported data from mother-baby cohorts in mainland China, with ≥1y follow-up after birth. We identified 315 papers, corresponding to 31 cohorts from 19 provinces/megacities.

RESULTS

All cohorts started in 1999-2017 (21 after 2010) and were set up with broad objectives or specific scientific focus. The baseline sample size varied, from <500 to >300,000 mothers. A majority of cohorts were initiated during pregnancy and followed children to <10y, only six to adolescence and none into adulthood. These cohorts mostly collected samples from mothers and babies, in addition to using interviews/questionnaires to collect information about pregnancy, birth and child health. Most cohorts were recruited from a single province/city. The large western region was understudied.

CONCLUSIONS

Mother-baby cohorts have developed rapidly in China, but usually with a short follow-up duration. Extending the follow-up of children and developing cross-cohort collaboration will increase the diversity, size and coverage of the sample, allow studying early influences on life-course health and identify targets for early intervention in the Chinese population.

Pre-pregnancy body mass index and glycated-hemoglobin with the risk of metabolic diseases in gestational diabetes: a prospective cohort study

Background

Metabolic diseases during pregnancy result in negative consequences for mothers. Pre-pregnancy body mass index (BMI) and late-pregnancy glycated-hemoglobin (HbA1c) are most important factors independently affecting the risk of gestational diabetes mellitus (GDM). However how both affect the combined risk of other metabolic diseases in women with GDM is unclear. The study aims to investigate the influence of pre-pregnancy BMI and pregnancy glycemic levels on other gestational metabolic diseases in women with GDM.

Methods

Pregnancies with GDM from January 2015 to December 2018 in the Xi'an longitudinal mother-child cohort study (XAMC) were retrospectively enrolled. Those without other metabolic diseases by the time of oral glucose tolerance test (OGTT) detection were finally recruited and divided into four groups by pre-pregnancy BMI (Underweight <18.5kg/m2; Normal weight 18.5-23.9 kg/m2; Overweight 24.0-27.9 kg/m2; Obesity ≥28.0 kg/m2, respectively) or two groups by HbA1c in late pregnancy (normal HbA1c<5.7%; high HbA1c≥5.7%). Multivariate logistic regression analysis was used to identify risk factors. Interaction between pre-pregnancy BMI (reference group 18.5-23.9 kg/m2) and HbA1c (reference group <5.7%) was determined using strata-specific analysis.

Results

A total of 8928 subjects with GDM were included, 16.2% of which had a composite of metabolic diseases. The pre-pregnancy overweight and obesity, compared with normal BMI, were linked to the elevated risk of the composite of metabolic diseases, particularly pre-eclampsia (both P <0.001) and gestational hypertension (both P <0.001). Meanwhile, patients with high HbA1c had an obvious higher risk of pre-eclampsia (P< 0.001) and gestational hypertension (P= 0.005) compared to those with normal HbA1c. In addition, there were significant interactions between pre-pregnancy BMI and HbA1c (P< 0.001). The OR of pre-pregnancy BMI≥ 28 kg/m2 and HbA1c≥ 5.7% was 4.46 (95% CI: 2.85, 6.99; P< 0.001). The risk of other metabolic diseases, except for pre-eclampsia (P= 0.003), was comparable between the two groups of patients with different HbA1c levels at normal pre-pregnancy BMI group. However, that was remarkably elevated in obese patients (P= 0.004), particularly the risk of gestational hypertension (P= 0.004).

Conclusion

Pre-pregnancy overweight/obesity and late-pregnancy high HbA1c increased the risk of other gestational metabolic diseases of women with GDM. Monitoring and controlling late-pregnancy HbA1c was effective in reducing metabolic diseases, particularly in those who were overweight/obese before conception.

The associations of ferritin, serum lipid and plasma glucose levels across pregnancy in women with gestational diabetes mellitus and newborn birth weight

BACKGROUND

Women with gestational diabetes mellitus (GDM) are at greater risk of abnormal birth weight. Since the level of biochemical indicators could often affect the intrauterine growth and development of the fetus, it is of great practical significance to understand the changes of biochemical levels across pregnancy in women with GDM and to find out the indicators that play an important role in predicting birth weight.

METHODS

The data source of this study was from the Xi'an Longitudinal Mother-Child Cohort study (XAMC), in which women with GDM with normal and high pre-pregnancy body mass index (BMI) and their newborns between January 1^st and March 31^st in 2018 were included. The data of ferritin, serum lipid profile and fasting plasma glucose (FPG) of mothers in the three trimesters of pregnancy, as well as birth weight of newborns were all collected from medical records. Multiple linear regression and multivariate logistic regression analyses were used to explore the association of the biochemical indexes and birth weight. A P value < 0.05 was considered statistically significant.

RESULTS

A total of 782 mother-infant pairs were finally included and divided into normal weight group (NG) (n = 530, 67.8%) and overweight/obesity group (OG) (n = 252, 32.2%) according to maternal pre-pregnancy BMI. The level of ferritin in both NG and OG decreased during pregnancy (P for trend < 0.001 for all), whereas the levels of total cholesterol (TC), high density cholesterol (HDL-C), low density cholesterol (LDL-C) and triglycerides (TG) all showed an upward trend (P for trend < 0.05 for all). The levels of FPG in the two groups remained in a relatively stable during the whole pregnancy even though it was higher in OG during the 2^nd and 3^rd trimesters, whilst HbAlc levels in NG women increased (P for trend = 0.043) during pregnancy. Meanwhile, the risk of macrosomia and large-for-gestational-age (LGA) increased with the increase of FPG level (P for trend < 0.05). Multivariate logistic regression analyses results showed that only FPG level in the 3^rd trimester was correlated with birth weight, with birth weight increased by 44.9 g for each SD increase in FPG level.

CONCLUSION

Maternal FPG in the 3^rd trimester is an independent predictor of newborn birth weight, and a higher level of that is associated with an increased risk of macrosomia and LGA.

What is an appropriate gestational weight gain for women with gestational diabetes mellitus: based on the adverse pregnancy outcomes of over 12 thousand participants?

BACKGROUND

Evidence showed possible benefits of a less gestational weight gain (GWG) than the US Institute of Medicine (IOM) recommendation in gestational diabetes mellitus (GDM) pregnancy. Here, we aimed to explore an appropriate GWG range in GDM women according to adverse pregnancy outcomes.

METHODS

We enrolled all the singleton GDM pregnant women (n = 14,213) from January 2015 to December 2018 in Xi'an, Northwest China. According to the pre-pregnancy body mass index (BMI), they were classified into the Underweight (< 18.5 kg/m²), Normal weight (18.5-24.9 kg/m²⁾, Overweight (25.0-29.9 kg/m²) and Obesity (≥ 30.0 kg/m²) group, respectively. Logistic regression analysis was used to calculate the odds ratio (OR) and 95% confidence intervals (95% CI). The appropriate ranges of GWG were determined based on a significant protective association (OR < 1).

RESULTS

Totally, 12,712 participants were finally recruited. There were 1180 (9.3%), 9134 (71.9%), 2097 (16.5%), and 301 (2.4%) patients in the Underweight, Normal weight, Overweight, and Obesity groups, respectively. Adverse outcomes increased with the elevation of pre-pregnancy BMI. Among them, the risk of cesarean section was the highest, followed by large for gestational age (LGA), small for gestational age (SGA), preeclampsia, and gestational hypertension. Through the analysis of the risk of adverse outcomes in continuous GWG categories in each group, an ideal GWG range obtained in this study was as follows: 10-15.9 kg, 8-11.9 kg, 6-7.9 kg, and -5-3.9 kg for the Underweight, Normal weight, Overweight and Obesity group, respectively. Furthermore, the ranges in this study were more protective for adverse outcomes than those from IOM.

CONCLUSIONS

Based on the adverse pregnancy outcomes of over 12 thousand participants, our findings showed a more stringent GWG range for GDM women than the IOM criteria recommendation.

Late-Pregnancy Dysglycemia After Negative Testing for Gestational Diabetes and Risk of the Large-for-Gestational-Age Newborns: A Nest Case-Control Study Based on the Xi'an Longitudinal Mother-Child Cohort Study

BACKGROUND

The implications of gestational diabetes mellitus (GDM) on the short- and long-term health outcomes of both mother and child have been extensively studied. However, studies related to negative Oral Glucose Tolerance Test (OGTT) results in the second trimester but dysglycemia in late pregnancy on maternal and infant pregnancy outcomes are rare.

METHODS

We conducted a nest case-control study within the Xi'an Longitudinal Mother-Child Cohort study (XAMC) to investigate the risk of adverse pregnancy outcomes in mothers and children with maternal negative mid-pregnancy OGTT results but high glycated hemoglobin (HbA_1c) levels (≥5.7%) in late pregnancy. All target women who delivered from January 1st, 2017 to December 31st, 2018 in Northwest Women's and Children's Hospital in Xi'an were enrolled as the case group (HbA_1c ≥ 5.7%). Others with HbA_1c < 5.7% but without GDM were selected as the control group (HbA_1c < 5.7%) by matching with the same delivery period. The logistic regression models were used to find out the risk factors of adverse pregnancy outcomes in the target population.

RESULTS

A total of 2,116 and 1,907 women were finally enrolled in the case and control groups, respectively. Compared to the control group, more newborns with macrosomia (9.2% vs 4.1%, P < 0.001) and large for gestational age (LGA) (23.7% vs. 13.5%, P < 0.001), but less small for gestational age (SGA) (4.4% vs. 6.1%, P = 0.017) were found in the case group. The differences in other outcomes were not statistically significant. The multiple logistic regression analysis showed that gestational age, fetal length, prenatal HbA_1c, and total cholesterol (TG) were independent risk factors for newborns with large-for-gestational-age (LGA). The case group had a 2.516-fold (95% CI, 1.692-3.739) risk of delivering LGA newborns compared to the control group.

CONCLUSION

The glycemic management during the late pregnancy of non-GDM women should be given special consideration to reduce the risk of overweight offspring at birth.