High-Dose Prenatal Vitamin D Aids Bone Mineralization In Offspring

High-dose vitamin D supplementation during pregnancy can improve bone mineralization in children up to 6 years of age, according to new findings.

Children whose mothers had been randomized to 2,800 international units of vitamin D per day had higher total bone mineral content (BMC), higher total body less head (TBLH) BMC and higher head bone mineral density (BMD) at 3 and 6 years of age compared to children whose mothers received the standard 400 IU/day dose, Dr. Hans Bisgaard of the University of Copenhagen and colleagues report in JAMA Pediatrics.

The findings are based on a prespecified secondary analysis of the Copenhagen Prospective Studies on Asthma in Childhood (COPSAC), which included 623 pregnant women and 584 offspring. Women in the study were all taking 400 IU/day of vitamin D, and were randomized to take an additional 2,400 IU or a placebo, starting in week 24 of pregnancy through the first week after birth.

Anthropometric data at 6 years were available for 517 children, and were similar for the low- and high-dose groups.

DXA scans were available for 244 children at 3 years of age. TBLH BMC was significantly higher for the vitamin D group compared with the placebo group (293.8 g vs. 288.8 g). Total body BMC was 526.2 g in the vitamin D group compared to 513.5 g with placebo (P=0.04).

DXA scans were available for 383 6-year-olds, and showed significantly higher TBLH BMC, head BMD, head BMC, total BMD and total BMC.

At both 3 and 6 years of age, the effects of vitamin D were largest for children whose mothers had insufficient vitamin D levels at baseline, and for those who were born during the winter.

Fifty-nine fractures occurred during follow-up, and there was a trend toward lower fracture incidence with vitamin D compared to placebo (7% vs. 11%, P=0.08).

"I have told my daughters to use high doses of vitamin D while they are pregnant," Dr. Bisgaard told Reuters Health in a telephone interview. He noted that the COPSAC trial found some protection against early asthma symptoms with prenatal high-dose vitamin D, which has also been shown to have dental benefits for offspring.

He added: "I think that the time is up to sit down and revise the recommendations. There are no side effects in this dose range."

In an editorial accompanying the study, Dr. Elisa Holmlund-Suila and colleagues from the University of Helsinki and Helsinki University Hospital urge caution, however.

"Previous observations of potential disadvantageous effects of high maternal vitamin D on offspring health outcomes are concerning," they write.

"Thus, before recommending 7-fold supplementation of vitamin D to pregnant women to improve offspring bone health, more research is required. Also, possible long-term adverse effects of high-dose vitamin D supplementation have to be investigated carefully," they conclude.

—Anne Harding

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