To systematically evaluate the relationship between gestational vitamin D deficiency and spontaneous abortion.

Databases including PubMed, Web of Science, Ebsco, Cochrane, Embase, CNKI, Wanfang database, China Biomedical Literature Service System, etc. were searched for cohort studies and case-control studies on the correlation between gestational vitamin D deficiency/insufficiency and abortion outcomes, respectively from the establishment of individual database to December 2021. Two investigators independently performed literature screening, data extraction and risk of bias assessment for included studies. Meta-analysis was conducted with RevMan 5.4.1 and Stata 15.1.

Eventually, 12 cohort studies and 5 case-control studies were included. A total of 19,308 pregnant women were enrolled, among whom 1 405 abortions were observed. 8 studies were published in Chinese and 9 in English. 10 studies were from China and 1 study each was from Iran, Egypt, Sweden, United States, Denmark, Turkey and Australia. The standards for vitamin D deficiency and the diagnostic criteria for miscarriage were basically the same across studies. After adjusting for confounding factors such as age and race, the meta-analysis showed that gestational vitamin D deficiency/insufficiency would increase the risk of miscarriage. A subgroup analysis of women with miscarriage in early pregnancy showed results consistent with that in overall population. No significant publication bias were identified via meta-analysis.

Gestational vitamin D deficiency and insufficiency are related to the occurrence of spontaneous abortion and can increase the risk of early spontaneous abortion.

Vitamin D; Pregnancy; Abortion; Meta-analysis