The purpose of this study to assess the effect of maternal vitamin D3 (cholecalciferol) supplementation on maternal HIV progression, small-for-gestational age infants, and infant stunting at 12 months postpartum for HIV-infected Tanzanian pregnant women who are receiving highly active antiretroviral therapy (HAART).

The study is a randomized, double-blind, placebo-controlled trial of maternal vitamin D3 (cholecalciferol) supplementation starting in the second trimester (12-27 weeks gestation) and continuing until 12 months postpartum among HIV-infected Tanzanian pregnant women who are receiving HAART. Eligible individuals are randomized to receive a) a vitamin D3 regimen consisting 3,000 IU of vitamin D3 taken orally once daily starting in the second trimester and continuing until 12 months postpartum or b) a placebo regimen taken orally once daily starting in the second trimester and continuing until 12 months postpartum. Mothers will be followed at study visits during pregnancy and mother/infant pairs will attend study visits from birth until trial discharge at 12 months postpartum.

Inclusion Criteria:

• Women aged ≥18 years old
• HIV-positive
• Receiving HAART
• Pregnant and of 12-27 weeks gestation (Second Trimester)
• Calcium levels in the normal physiologic range (≤2.6 mmol/L)

Exclusion Criteria:

• Enrolled in any other clinical trial