Background

Disturbed sleep is a significant health issue for pregnant women. Inadequate vitamin D intake is common among pregnant women and can affect many bodily systems. The purpose of this cross-sectional study was to test the hypothesis that serum vitamin D levels are low in pregnant women who have poor sleep quality in their last trimester.

Methods

We enrolled 92 pregnant women who were admitted to the Maternity Clinic of Turgut Ozal University (Ankara, Turkey) in their last trimester. Venous blood sampling was performed to determine serum 25-hydroxyvitamin D levels. Sleep quality was measured by the Pittsburgh Sleep Questionnaire. The Student t test and Chi-square test were used to evaluate the relationships between variables. Logistic regression analysis was used to identify independent predictors of the vitamin D level.

Results

The median score of the Pittsburgh Sleep Questionnaire was 6.2±3.3 (range, 1–17). We determined that 43.5%(40) of participants had poor sleep quality. The mean number of sleep hours at night was 8.6±1 hours (range, 6.30–11 hours), and the mean sleep latency was 20.3±12.7 minutes (range, 5–60 minutes). Vitamin D levels were measured for 87 participants; the median serum level of 25 (OH) vitamin D was 22.9±16.2 ng/mL (range, 4.9–99 ng/mL). Among all patients, we did not determine any significance between the vitamin D-deficient group and the non–vitamin D-deficient group with regard to the Pittsburgh Sleep Questionnaire Inventory (PSQI) total score and subcomponents scores of the questionnaire (p> 0.05). Among 37 patients with poor sleep quality and for whom the vitamin D level was measured, 56.8%(21) women had vitamin D deficiency, and 81%(30) women had vitamin D insufficiency. However, we did not find any significance between participants with poor sleep and participants with good sleep quality with regard to age, occupational status, relationship with her partner, prepregnancy body mass index (BMI), weight gain during pregnancy, being primiparus, length of labor, and mode of delivery. Our findings further showed that being in a low income family was associated with poor sleep quality.

Conclusion

Inadequate vitamin D and poor sleep quality are prevalent in pregnant women, but low levels of vitamin D are not associated with poor sleep quality. Further studies with larger sample sizes and studies that include preterm deliveries and special sleep disorders should be performed to understand this issue better.