Objective To
assess the effect of 25-hydroxyvitamin D (25-OHD) levels on pregnancy
outcomes and birth variables.
Data
sources Medline
(1966 to August 2012), PubMed (2008 to August 2012), Embase (1980 to
August 2012), CINAHL (1981 to August 2012), the Cochrane database of
systematic reviews, and the Cochrane database of registered clinical
trials.
Study
selection Studies
reporting on the association between serum 25-OHD levels during
pregnancy and the outcomes of interest (pre-eclampsia, gestational
diabetes, bacterial vaginosis, caesarean section, small for
gestational age infants, birth weight, birth length, and head
circumference).
Data
extraction Two
authors independently extracted data from original research articles,
including key indicators of study quality. We pooled the most
adjusted odds ratios and weighted mean differences. Associations were
tested in subgroups representing different patient characteristics
and study quality.
Results 3357
studies were identified and reviewed for eligibility. 31 eligible
studies were included in the final analysis. Insufficient serum
levels of 25-OHD were associated with gestational diabetes (pooled
odds ratio 1.49, 95% confidence interval 1.18 to 1.89), pre-eclampsia
(1.79, 1.25 to 2.58), and small for gestational age infants (1.85,
1.52 to 2.26). Pregnant women with low serum 25-OHD levels had an
increased risk of bacterial vaginosis and low birthweight infants but
not delivery by caesarean section.
Conclusion Vitamin
D insufficiency is associated with an increased risk of gestational
diabetes, pre-eclampsia, and small for gestational age infants.
Pregnant women with low 25-OHD levels had an increased risk of
bacterial vaginosis and lower birth weight infants, but not delivery
by caesarean section.
