Introduction:
Deficiency of vitamin D in pregnancy leads to higher incidences of preeclampsia, gestational diabetes, preterm birth, bacterial vaginosis, and also affects the health of the infants. According to Polish recommendations published in 2009, vitamin D supplementation in pregnant women should be provided from the 2nd trimester of pregnancy in daily dose of 800–1000 IU. The aim of the presented study is: 1) to estimate how many pregnant women comply with those recommendations and 2) to determine the 25(OH)D levels in pregnant women.

Patients and methods:
The study included 88 pregnant women, aged 20–40 years, between 12–35 week of gestation. Vitamin D concentrations [25(OH)D] were measured by a direct electrochemiluminescence immunoassay (Elecsys, Roche).

Results:
31 of 88 pregnant women (35.2%) did not use any supplementation. Mean level of 25(OH)D was 28.8±14.8 ng/mL (range from 4.0 – 77.5 ng/mL). Vitamin D deficiency, defined as 25(OH)D concentration below 20 ng/mL, was found in 31.8% of the women (28/88). Insufficiency of vitamin D [25(OH)D concentration between 20–30 ng/mL] was present in 26.1% of the women (23/88). Optimal level of 25(OH)D (over 30 ng/mL) was present in 37/88 (42.0% women). Hence, in 46.2% of women taking vitamin D supplementation, the levels of 25(OH)D were still below 30 ng/mL.

Conclusions:
Supplementation of vitamin D in the investigated group was inadequate. More than 35% of pregnant women did not take any supplements, while half of the subjects who had declared taking vitamin D, failed to achieve optimal serum 25(OH)D concentration.