Postnatal evaluation of vitamin D and bone health in women who were vitamin D-deficient in pregnancy, and in their infants

Abstract

Objective: To determine the postnatal vitamin D status and bone health of women identified as vitamin D-deficient in pregnancy, and of their infants.

Design and participants: Retrospective audit conducted between 27 August and 5 November 2003. The study included women delivering between August and October 2002 at the Royal Women's Hospital, Melbourne, who had had a 25-hydroxyvitamin D (25-[OH]D) level < 30 nmol/L in pregnancy, and their infants at age 4-10 months.

Setting: The outpatient clinic at the Royal Children's Hospital, Melbourne.

Main outcome measures: Maternal and infant serum levels of vitamin D, total alkaline phosphatase (tALP), parathyroid hormone (PTH), calcium and phosphorus; x-ray results in children with clinical or laboratory findings suggestive of rickets.

Results: Of 69 mother-infant pairs invited to participate, 47 (68%) attended. All 47 women had 25-(OH)D levels < 50 nmol/L, and 39 (83%) had levels < 30 nmol/L. Vitamin D supplements had been prescribed in pregnancy for 35 women (74%), and 19/35 reported having taken them as prescribed. None had continued to take supplements postnatally, but one had recently started taking them again. Among 45 infants from whom blood samples were successfully obtained, 18 (40%) had 25-(OH)D levels < 50 nmol/L, and 14 (31%) had levels < 30 nmol/L. Twelve of 16 breastfed infants had 25-(OH)D levels < 30 nmol/L, compared with 2/29 fed formula milk (P = 0.001).

Conclusions: Most mothers who had been vitamin D-deficient in pregnancy were also deficient postnatally, indicating that treatment offered, counselling and/or treatment compliance were inadequate. Their infants, especially if breastfed, were at high risk of vitamin D deficiency and increased bone formation. Breastfed infants of mothers at high risk of vitamin D deficiency should receive vitamin D supplements.