【Abstract】
Objectives:The relative contributions of vitamin D status to pregnancy complications are not fully understood. We investigated the correlation between vitamin D status and pregnancy outcomes.
Design: Prospective analysis of cases
Setting: China
Population or Sample: A total of 1766 pregnant women were admitted to The Eighth Affiliated Hospital, Sun Yat-sen University and Guangdong Women and Children Hospital between January 2019 and December 2020.
Methods: This prospective cohort study was performed on women who paid antennal visits during their whole gestation. Serum 25-hydroxyvitamin D [25(OH)D] concentrations were measured among women before 24 weeks of gestation. Associations between maternal vitamin D status, maternal characteristics, and pregnancy outcomes were assessed. The adjusted odds ratio (OR) for adverse pregnancy outcomes was calculated using the logistic regression analysis.
Results: Among all participants, 192(10.87%), 1023(57.93%) and 551(31.20%) were defined as vitamin D sufficiency, insufficiency, and deficiency, respectively. There was no significant difference in vitamin D between pregnant women with adverse pregnancy outcomes and those without adverse pregnancy outcome. Neither vitamin D deficiency nor insufficiency was associated with adverse pregnancy outcomes compared with vitamin D sufficiency. Risks of adverse outcomes were as follows: GDM (OR=0.72 95%CI 0.46-1.14; OR=0.86 95%CI 0.57-1.30), SGA (OR=1.38 95%CI 0.73-2.60; OR=1.28 95%CI 0.70-2.34), early preterm delivery (OR=0.59 95%CI 0.13-2.70; OR=0.84 95%CI 0.23-3.00), PE (OR=3.44 95%CI 0.43-27.52; OR=2.40 95%CI 0.31-18.50), and postpartum hemorrhage (OR=0.58 95%CI 0.33-1.03; OR=0.81 95%CI 0.49-1.35).
Conclusions: Low vitamin D status may not be associated with adverse pregnancy outcomes. Vitamin D screening in all pregnant women seems not reasonable.
Keywords: Vitamin D;gestational diabetes mellitus; small for gestational age; preterm delivery; 25-hydroxyvitamin D; pregnancy 
【Introduction】
Vitamin D is an essential nutritional factor, which has received increasing attention in recent years, due to its primary role in bone remodeling, calcium homeostasis, and muscle functioning[1].During pregnancy, vitamin D plays an important role in maternal metabolism and embryogenesis, especially fetal skeletal development and calcium homeostasis[2]. Vitamin D deficiency means that the serum levels of vitamin D are inadequate to support the daily body needs[3]. Numerous clinical studies have reported that large proportions of global populations are vitamin D “deficiency ”, including pregnant women[1, 4, 5].Some researches have also concluded many adverse effects of maternal vitamin D deficiency[6-8]. Animal experiments showed that vitamin D deficiency during pregnancy could lead to reproductive dysfunction and neurobehavioral developmental disorders in adult offspring[9].
Vitamin D level is commonly assessed by the measurement of 25-hydroxyvitamin D[25(OH)D] level, which is considered the best marker of vitamin D status. According to the recommendation and consensus of the Committee of the Institute of Medicine (IOM, USA), most experts agree to define vitamin D insufficiency as 25(OH)D between 30-49.9nmol/L, and 25(OH)D levels of <30nmol/L are considered to be indicative of vitamin D deficiency[10]. This array of values is for everyone: children or adults, pregnant or not,because vitamin D metabolism is markedly different during pregnancy compared to nonpregnancy, significant changes in calcium and vitamin D metabolism occur during pregnancy to meet the needs of growing fetuses[11]. Unfortunately, it is unclear whether the recommended 25(OH)D levels discussed above are suitable for pregnant women. In fact, vitamin D insufficiency and deficiency are very common in pregnant women and newborns population, almost one in three newborns or one in five pregnant women were found below 25nmol/L[7]. However, it is still controversial whether vitamin D “deficiency” or “insufficiency” as defined by the IOM criteria is really related to adverse pregnant outcomes.
In this prospective study of two tertiary hospitals in South China, our aim was to investigate the association between vitamin D status before 24 gestational weeks and adverse pregnancy outcomes that were mainly reported recent years[12] [gestational diabetes mellitus (GDM), small for gestational age (SGA), early preterm delivery (preterm delivery before 34 weeks), preeclampsia (PE), and postpartum hemorrhage].