Vitamin D is important for Pregnant...6

Vitamin D is important for Pregnant...6

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2... Low Vitamin D could make Tough Pregnancy

Pregnant women with insufficient levels of vitamin D may be at increased risk of gestational diabetes, preeclampsia, and having infants small for their gestational age, a new meta-analysis showed.

They also may have an increased chance of bacterial vaginosis and lower-birth-weight infants, according to Doreen Rabi, MD, of the University of Calgary in Canada, and colleagues.

On the other hand, they were not more likely to deliver by cesarean section, Rabi and colleagues reported online in BMJ.

Low levels of 25-hydroxyvitamin D (25-OHD) have been associated with adverse health outcomes, including those in pregnancy, the researchers noted, but understanding of the clinical implications is limited.

However, published research on vitamin D insufficiency in pregnancy has been "growing rapidly," requiring systematic review and meta-analysis to clarify its clinical importance.

They found 31 studies reporting on links between serum 25-OHD levels during pregnancy and pregnancy outcomes (defined as preeclampsia, gestational diabetes, bacterial vaginosis, and C-section) and birth variables (small for gestational age, birth weight, birth length, and head circumference).

Ten studies reported on gestational diabetes, 10 reported on birth variable, nine on preeclampsia, three on bacterial vaginosis, and two on C-section. One study had data on two of the outcomes of interest.

All the studies -- with between 95 and 1,100 participants -- were published between 1980 and 2012. Fifteen were case-control studies, 11 were cohort studies, and five had other designs, but all used a comparison group.

For the analysis of pregnancy outcomes, Rabi and colleagues defined vitamin D insufficiency to be a serum 25-OHD concentration of less than 75 nmol/L, while for birth variables, they defined it as less than 37.5 nmol/L.

The analyses showed that insufficient vitamin 25-OHD was associated with:

• Gestational diabetes: pooled odds ratio 1.49 (95% CI 1.18 to 1.89)
• Preeclampsia: pooled OR 1.79 (95% CI 1.25 to 2.58)
• Having an infant who was small for gestational age: pooled OR 1.85 (95% CI 1.52 to 2.26)

Three studies looked at bacterial vaginosis and all found an increased risk for women with low 25-OHD, but differences in statistical reporting meant a meta-analysis couldn't be performed, Rabi and colleagues explained.

The four studies that reported on birth weight found that infants of mothers with low 25-OHD concentrations averaged 130 g lighter (random weighted mean difference −130.92 g, 95% CI −186.69 to −75.14 g) than those of mothers in the normal range, but birth length and head circumference did not differ significantly.

Of the two studies that looked at the risk of C-section, one found an increased risk for mothers with low 25-OHD and one did not.

Overall, the findings "support a goal of vitamin D sufficiency for all pregnant women," commented Robyn Lucas, MBChB, PhD, of the Australian National University in Canberra, and colleagues.

In some parts of the world – notably Asia and Africa – reaching such a goal might lead to important gains in health, if there are causal links between vitamin D deficiency and adverse maternal and neonatal outcomes, they commented in an accompanying editorial.

But current evidence poses challenges because it's derived mainly from observational studies and small trials, they cautioned.

Well-designed randomized trials are needed to "clarify the causal association" between vitamin D and health, they commented. "This is particularly needed to delineate the importance of vitamin D in pregnancy with its potentially lifelong effects on the health of offspring."