The purpose of this study is to look at the effects of tenofovir disoproxil fumarate (an anti-HIV medication) on the bone health and kidneys of women with HIV during pregnancy and while breastfeeding. The study will also look at the changes in overall health, bone health and how the kidneys work in the infants of these women.

A small number of adults (who are not pregnant) and children who take anti-HIV medications develop problems with their kidneys and with the strength of their bones. These problems may be more common when tenofovir disoproxil fumarate (TDF) is used. Studies about these bone and kidney effects have not been done in pregnant and breastfeeding women and their infants.

This is a substudy of a larger study (IMPAACT 1077 PROMISE [Promoting Maternal and Infant Survival Everywhere]) to evaluate the safety of anti-HIV medications used in pregnancy and during breastfeeding. Only participants in the larger study randomly assigned to receive maternal tenofovir disoproxil fumarate (TDF) or no maternal TDF during pregnancy or during breastfeeding will be enrolled in this substudy.

This substudy will look at two groups of participants:

• An antepartum exposure group to look at the effects of TDF during pregnancy
• A postpartum exposure group to look at the effects of TDF during breastfeeding

All mother-infant pairs in the substudy will be followed for 74 weeks after delivery. During this time, the women and their infants will have medical checkups and tests. The tests will include tests of blood, urine, cord blood, and breast milk. Some of the women and infants will have a special x-ray called a dual energy e-ray absorptiometry (DXA) scan to measure bone strength. The timing of the tests-at enrollment, at delivery, at 6, 10, 26, or 74 weeks-will vary dependent on which part of this substudy women and infants are enrolled in. Those in charge of the substudy will try to schedule medical visits and tests at the same time as tests scheduled for the larger IMPAACT 1077 study.

Antepartum (AP) Part of Study (TDF Exposure During Pregnancy)

Inclusion Criteria:

• Mother-infant pair enrolled in 1077BA or 1077FA
• At a clinical site that has been approved as a P1084s DXA site
• Enrolled in the substudy up to the Week 2 visit of 1077BA/1077FA (within 21 days after 1077BA/1077FA study entry) and prior to the start of labor
• Willing and able to provide written informed consent to participate in this substudy

Exclusion Criteria:

• None

Postpartum (PP) Part of Substudy (TDF Exposure During Breastfeeding) (Note: this applies only to the new enrollment to P1084s, i.e., those who were not enrolled to P1084s while on the AP component)

Inclusion Criteria:

• Mother and their infant enrolled in 1077BP
• At a clinical site that has been approved as a P1084s DXA site
• Enrolled in the substudy within 6 to 14 days of delivery, on the same day as enrollment in 1077BP
• Willing and able to provide written informed consent to participate in this substudy

Exclusion Criteria:

• TDF exposure during pregnancy [NOTE: TDF use for up to 12 days beginning at labor allowed]
• Enrolled in the AP part of P1084s

For antepartum (AP) exposure part of P1084s: Mother/infant pairs enrolled in the antepartum components of 1077BF or 1077FF (1077BA and 1077FA respectively) at African clinical sites approved as P1084s DXA sites.

For postpartum (PP) exposure part of P1084s: Mothers and their infants enrolled in the postpartum component of 1077BF (107BP) at African clinical sites approved as P1084s DXA sites.