The Effect Of Serum Vitamin D Concentration During Pregnancy On Neonatal Birth Outcomes

Objective:To describe the current status of vitamin D levels in healthy pregnant women in Ma’anshan City by measuring serum concentrations of vitamin D,and to investigate the association between vitamin D concentrations and neonatal birth outcomes,in order to provide reference for the development of public health interventions.Methods:The population of this study was obtained from the birth cohort of Ma’anshan City from May 1,2021 to Apr 31,2022,and the basic demographic data and health status of pregnant women during pregnancy were collected in first,second and third trimesters,respectively.With the informed consent of pregnant women and their families,we need to collect 5 mL of maternal blood at 9-14 weeks,22-27 weeks,and 29-34 weeks,respectively,isolate and preserve the serum for the detection of vitamin D concentration;once the delivery finished,the neonatal birth data can be collected from the obstetric records and maternal health handbook.After all data were obtained,firstly,we used t-test,χ~2,and ANOVA for univariate analysis of the underlying demographic data and health status during pregnancy with birth outcomes;secondly,we used multiple linear regression and multifactorial logistic regression to explore the association between vitamin D concentration and birth outcomes at different trimesters;subsequently,adverse birth outcomes were analyzed separately,using restricted cubic spline curves to explore the trend of vitamin D concentration at different trimesters with the risk of adverse birth outcomes;finally,we used the three tested vitamin D concentrations as longitudinal data and a linear mixed-effects model that included gestational age(weeks)as a random effect,from which the best linear unbiased prediction(BLUP)was obtained,mainly to generate vitamin D concentration prediction slope and intercept,and the generated slope and intercept were incorporated into the regression model as exposures to explore the association between the slope and intercept of vitamin D concentration prediction and birth outcome.Results:(1)A total of 1129 healthy pregnant women were included in this study,and1129 data of vitamin D concentrations were detected in first trimester with a mean concentration(standard deviation)of 20.86(3.24)ng/mL,1101 data of vitamin D concentrations in second trimester with a mean concentration(standard deviation)of24.28(7.29)ng/mL,and vitamin D concentrations in third trimester with a mean concentration(standard deviation)of 27.63(6.91)ng/mL.In addition,of the 1129newborns,632(56.0%)were male than 497(44.0%)were female;the mean birth weight(standard deviation)was 3309.91(464.94)g,the mean birth length(standard deviation)was 49.82(2.060)cm,and the mean(standard deviation)33.85(1.52)cm,mean birth weight z-score(standard deviation)0.24(0.91),mean birth length z-score(standard deviation)0.46(1.00),mean birth head circumference z-score(standard deviation)0.12(1.05);among them,The prevalence of small for gestational age(SGA),large for gestational age(LGA),low birth weight(LBW),and preterm birth(PTB)were 6.4%,15.4%,4.4%,and 5.4%,respectively.(2)Regression analysis of vitamin D concentrations and birth outcomes at different trimesters showed that vitamin D concentrations in first trimester were associated with birth weight(β=9.910,95%CI:1.603-18.112),as well as an inverse association between serum vitamin D concentrations and the risk of PTB at each trimester:first trimester(OR=0.691,95%CI.0.633-0.754),second trimester(OR=0.927,95%CI:0.890-0.971),and third trimester(OR=0.781,95%CI:0.732-0.850).(3)Restricted cubic spline curves showed that the risk of PTB decreased with increasing vitamin D concentrations during pregnancy;and the cutoff value of vitamin D concentration(at OR=1)increased with increasing gestation,with 20.81 ng/mL in the first trimester,23.50 ng/mL in the second trimester,and 27.22 ng/mL in the third trimester.this study did not find an association between vitamin D concentrations at different gestational periods and the risk of their occurrence.(4)In a longitudinal study of vitamin D concentration data throughout pregnancy,it was found that the intercept of vitamin D concentration(serum vitamin D concentration at gestational age of 0 weeks)was positively correlated with birth weight(β=48.501,95%CI:30.212-66.891),and was associated with the risk of LBW(OR=0.681,95%CI:0.563-0.823),PTB(OR=0.443,95%CI:0.363-0.541)risk of occurrence;the slope of vitamin D concentration(rate of vitamin D concentration during pregnancy)was associated with birth weight(β=305.754,95%CI:208.411-408.102),birth length z-score(β=0.112,95%CI:0.033-0.327),and birth weight z-score(β=0.154,95%CI:0.077-0.323)were associated.A higher slope was associated with a lower risk of preterm birth(OR=0.533,95%CI:0.643-0.764).Conclusion:Our prospective cohort study showed that serum vitamin D concentrations in each trimester were associated with the risk of PTB,and that as serum vitamin D concentrations increased the risk of PTB decreased.In addition,only serum vitamin D concentrations in first trimester were associated with newborn birth weight.Regarding the rate of change of vitamin D concentration during pregnancy,we found an association with birth weight,birth length z-score,birth weight z-score,and PTB.Therefore,in order to reduce the occurrence of adverse birth outcomes and reduce the public health burden,health authorities should strengthen the monitoring of vitamin D concentrations before and during pregnancy and develop targeted interventions for pregnant women with vitamin D deficiency or insufficiency.