Risk of Rickets Reduced With Maternal Vitamin D Supplementation

Women who supplemented vitamin D both during pregnancy and six months postpartum reduced their babies’ chances of developing rickets, a recent study shows.

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Increasing vitamin D supplementation during pregnancy can drastically reduce the risk of an infant developing rickets, a childhood condition marked by weakened, softened bones.

Results of a recent randomized trial published in Pediatrics by researchers in Canada and Bangladesh found that vitamin D supplementation before and after pregnancy offered the most benefit to children in preventing rickets, as opposed to supplementation that ended at delivery.

A Common Bone Disease

Rickets is one of the most common causes of pediatric bone disease worldwide. It usually results from extreme and prolonged vitamin D deficiency. During pregnancy or an infant’s early childhood, vitamin D helps a growing fetus or infant absorb calcium and phosphorus from food. If enough vitamin D isn’t available, it can be challenging to maintain enough of these minerals in the bones, which can cause rickets.

The condition can cause delayed growth and motor skills, spinal, pelvic, and leg pain, and muscle weakness. Rickets typically affects areas of growing tissue at the ends of bones, which softens them and can cause skeletal deformities. These might look like bowed legs, knocked knees, thickened wrists and ankles, or a projecting breastbone.

Maximum Recommended Daily Amount During and After Pregnancy

For this double-blind study conducted between 2014 and 2018, 1,300 pregnant women from Dhaka, Bangladesh, in their second trimester were divided into five groups and randomly given either a placebo or vitamin D supplementation at levels starting at about 600 IU per day. The groups were as follows:

• One group was given 4,200 IU per week and a placebo postpartum.
• A second group was given 16,800 IU per week, followed by a placebo after delivery.
• The third was given 28,000 IU per week, followed by a postpartum placebo.
• A fourth group was given 28,000 IU per week up to six months postpartum.
• The fifth was given a placebo throughout the study.

Among all the infants, 4.9 percent developed rickets after birth. Infants whose mothers were given 28,000 IU of vitamin D per week throughout pregnancy and for six months after giving birth were less likely to develop rickets. The research team did not find significant differences between the groups of women who received any amount of vitamin D supplementation during pregnancy and nothing afterward and the placebo group.

“Maternal prenatal supplementation alone at any dose, without postpartum continuation, did not significantly decrease the risk of biochemical rickets,” the researchers wrote.

The prevalence of rickets was highest in children whose mothers received the placebo.

The research team concluded that “high-dose maternal postpartum vitamin D supplementation may serve as a viable public health strategy for rickets prevention” but added that additional research is warranted to fine-tune the right amount of vitamin D needed for optimum rickets prevention.

The study’s findings mirror U.S. guidelines for how much vitamin D should be supplemented during pregnancy. Most prenatal vitamins typically contain 400 to 600 international units (IU) of vitamin D, which would be the same as what was tested in one group in the study (600 IU per day). However, most health authorities agree that supplementing vitamin D is safe in dosages up to 4,000 IU per day during pregnancy or lactation, according to the American College of Obstetricians and Gynecologists.

Other Risk Factors for Rickets

Aside from maternal vitamin D deficiency during pregnancy, if a woman exclusively breastfeeds her baby and the breast milk doesn’t contain enough vitamin D, a child could be at risk of developing rickets.

Other risk factors include living in areas with less sunlight, having darker skin that is less able to convert sunlight into vitamin D, and taking certain medications that can interfere with the body’s ability to use vitamin D.