Role of vitamin D on gestational hypertension, diabetes mellitus, timing and mode of delivery.

Objective: To determine the efficacy of VD in preventing the development of gestational diabetes mellitus (GDM) and pregnancy-induced hypertension (PIH). The secondary purpose is to investigate the effect of VD on the mode and time of delivery.

Patients And Methods: A vitamin D value of <20 ng/mL during pregnancy is considered a deficiency according to the Endocrine Society, and 400-600 IU/day VD replacement is recommended. Forty patients whose serum VD levels were below 20 ng/mL during routine pregnancy follow-up and who were planned for VD replacement therapy were included in the study. They were divided into two equal groups with 20 patients in each group. Twenty pregnant women with serum VD levels greater than 20 ng/mL were considered as the control group. While 400 IU/day VD replacement was applied to the patients in Group 1, 600 IU/day VD was given to Group 2. Group 3 consisted of control patients who did not undergo VD replacement. VD replacement was continued from the 14th week of pregnancy until delivery. Each group of participants was screened with a 50-g GCT at 24-28 weeks of gestation. Following 50-g GCT if serum glucose level was found >140 mg/dL, patients underwent 100-g OGTT. GDM was diagnosed in the presence of at least two of the following results: fasting serum glucose ≥92 mg/dL and/or 1-hour glycemia ≥180 mg/dL, and/or 2-hour glycemia ≥153 mg/dL. PIH was defined as systolic blood pressure >140 mmHg and diastolic blood pressure >90 mmHg. Patients in each group delivered by cesarean section or normal vaginal route. In addition to the incidence of PIH and GDM, the time and mode of delivery were recorded.

Results: PIH was detected in two patients in each of the 400 IU/day and 600 IU/day vitamin D replacement groups (10%). In the control group, PIH developed in 3 patients (15%). Although PIH was detected in an extra case in the control group, no significant difference was found between the replacement group and the control group in terms of PIH (p<0.44). While GDM was not detected in the 400 IU/day vitamin D group, GDM was detected in one patient (5%) in the 600 IU/day vitamin D group. No case of GDM was found in the control group either. There was no significant difference between the VD replacement and the control groups in terms of GDM rates. No significant difference was found between the VD replacement and the control groups in terms of mode of delivery. While the C/S ratio was 65% in the 400 IU/day vitamin D group, this ratio was 75% in the 600 IU/day vitamin D group. There was an insignificant trend of increase in C/S ratios in the group given 600 IU/day of vitamin D. The C/S ratio of the control group, which could not be given VD replacement, was found to be 70%.

Conclusions: VD replacement therapy during pregnancy does not prevent the development of PIH and GDM, and does not significantly contribute to the time and mode of delivery.