Prevalence of Vitamin D Deficiency in Pregnant Women: Systematic Review and Meta-analysis

CONTEXT: Vitamin D is an essential steroid prehormone whose effects have garnered significant interest during pregnancy and lactation. Adequate vitamin D levels are crucial for embryonic implantation, immune modulation, and preventing adverse maternal outcomes such as preeclampsia, gestational diabetes, and preterm birth. OBJECTIVES: To estimate the prevalence of vitamin D deficiency in each trimester of pregnancy. DATA SOURCES: This is a systematic review and meta-analysis, conducted according to the PRISMA guidelines. Online databases were searched from inception to July 2023, including Medline/PubMed, Embase, and LILACS. DATA EXTRACTION: All English, Spanish, and Portuguese articles that specified the prevalence of vitamin D deficiency in each of the 3 trimesters of pregnancy were included. All screening and data extraction were performed independently by 2 authors. Risk-of-bias assessment was performed using the Newcastle-Ottawa Scale. DATA ANALYSIS: A total of 2627 articles were retrieved, and after evaluating eligibility criteria, 116 full-text articles were included. These comprised observational studies, totaling 127 290 pregnant women who underwent serum 25(OH)D evaluation. Vitamin D deficiency is a common condition among pregnant women. The meta-analysis revealed that 68% (95% CI, 60%-76%) of pregnant women had 25(OH)D <30 ng/mL in the first trimester, 81% (95% CI, 74%-87%) in the second trimester, and 70% (95% CI, 64%-75%) in the third trimester, indicating a widespread deficiency of this vitamin. CONCLUSION: A thorough analysis of the studies included in this review shows that hypovitaminosis D during pregnancy is a highly prevalent condition that occurs in all 3 trimesters. Given this high prevalence, these findings may be valuable for planning public health policies aimed at pregnant women. SYSTEMATIC REVIEW REGISTRATION: PROSPERO registration no. CRD42022343256.