This study was conducted within the Shanghai Preconception Cohort (SPCC; NCT027step step three7644) that aims to investigate the associations between periconceptional maternal key nutrients and neonatal health outcomes, including congenital heart disease (20). Two subcohorts consisting of 938 and 458 subjects were derived for studying the associations of RBC folate with congenital heart diseases and infant atopic dermatitis. These two subcohorts thus formed the source of our study population. We restricted our study sample to pregnancies with folate and vitamin Ba dozen measurements examined at recruitment between 9 and 13 gestational weeks and with three glucose measurements under an oral glucose tolerance test (OGTT), resulting in 1,058 pregnancies included in the final analysis.
Standard services was basically acquired from the a standardized care about-advertised questionnaire thru face-to-deal with interviewers. The newest preconceptional Bmi was determined due to thinking-report prepregnancy pounds and you will peak. Smoking coverage are defined as mind-cigarette smoker or confronted by secondhand tobacco during pregnancy. Alcoholic beverages drinking is actually recognized as taking one liquor 3 months just before or while pregnant. FAS is actually defined as a frequent consumption away from folic acidic pills or material vitamin supplements pursuing the last menstrual cycle and during the maternity. The new folic acidic tablet include eight hundred ?g/pill regarding folic acid, as well as the compound nutritional supplements incorporate eight hundred ?g/tablet or 800 ?g/pill depending on the labels. Created advised agree is actually obtained from for every study topic prior to recruitment. This research try approved by the Stability Panel of your own Children’s Health away from Fudan School (Shanghai, China).
Diagnosis of GDM
All of the expectant mothers undergone good 75-g OGTT throughout twenty four–twenty eight gestational weeks, and analysis of GDM was developed when some of the adopting the standards was indeed satisfied with respect to the pointers of one’s Around the globe Connection of the Diabetes and you will Maternity Analysis Communities Opinion Committee (4): smooth glucose ?5.step one mmol/L, 1-h sugar ?10.0 mmol/L, otherwise 2-h glucose ?8.5 mmol/L.
The details of blood sample collection and nutritious biomarker measurements were described elsewhere (20). Briefly, the remaining blood samples after routine examinations at the first antenatal visit were collected by trained staff. These samples were temporarily stored in a refrigerator at 4°C for dispensing within 6 h and were transferred to another refrigerator at ?20°C. Serum and whole blood were then transported by trained investigators to the central laboratory for storage in freezers at ?80°C. Given the effect of light on folate measurements, lightproof tubes completely protected from light were used when transported and stored. RBC folate, serum folate, and vitamin Bseveral levels were measured in an ETDA anticoagulated blood sample according to a standard protocol 
. These biomarkers were measured using electrochemiluminescence assays (ARCHITECT i2000SR Analyzer; Abbott Laboratories) by professional staff. Three standard solutions (quality controls [QC]1, QC2, and QC3) were used as daily QC. The interassay coefficient of variation of QC1–QC3 for serum folate, vitamin B12, and RBC folate was <7.5%, and the intra-assay coefficient of variation was <6.5% for the entire study population.
Analytical Investigation
Continuous data were summarized as mean (SD) or median (interquartile range), and categorical data were displayed as percentages. An unpaired Student t test was used to test the differences in quantitative variables with a normal distribution. Otherwise, the equivalent nonparametric test was used. Categorical variables were compared with ? 2 tests. RBC folate concentrations >400 ng/mL (906 nmol/L) have been recommended as the optimal cutoff level for preventing NTDs in women of reproductive age (21). Additionally, RBC folate concentrations >600 ng/mL have been chosen as a cutoff for high RBC folate according to the Canadian Health Measures Survey (22). Accordingly, RBC folate concentrations were categorized as <400, 400–600, and ?600 ng/mL in the current study. Vitamin B12 and serum folate were categorized into tertiles because there is no specified cutoff for pregnancy. We used multivariable logistic regression analyses to investigate the associations of RBC folate, serum folate, and vitamin B12 with GDM and treated these biomarkers as continuous and categorical variables, with adjustment for age, preconceptional BMI, family history of diabetes, smoking exposure, and drinking status. To further examine the effects of combinations of folate and vitamin B12 status on the risk of GDM, we used percentiles of RBC folate, serum folate, and vitamin B12 to derive ratios of RBC folate/vitamin B12 and serum folate/vitamin B12. Percentile ratios were categorized into tertiles for the association analyses with the GDM risk. According to previous studies (19), the folate/vitamin B12 ratio was also calculated based on their raw data. Moreover, the restricted cubic spline (RCS) regression model with assumed three knots was used to outline the potential nonlinear relations among continuous RBC folate, vitamin B12, and GDM risk. The association of serum folate at the time of OGTT with GDM based on a subgroup of our study subjects (n = 458) was also conducted. Serum folate change was calculated by the levels in early pregnancy subtracted by the levels in midgestation. Odds ratio (OR) and 95% CI were reported. Correlation analysis was used to evaluate the relationship among RBC folate, vitamin B12, fasting serum glucose, and 1-h and 2-h serum glucose. Stata version 16.0 and R package (version 3.6.1) were used for all statistical analyses. A two-tailed P value of 0.05 was defined as statistical significance.