African-American Bone Metabolism and Lactation Study

New African-American mothers who are either almost exclusively breast-feeding or bottle-feeding; normal controls to match the lactating mothers

Inclusion Criteria:

• Group 1: Post-partum (singleton pregnancy) African-American women who are exclusively breastfeeding, defined as 1 or fewer bottles of supplemental formula/day.
• Group 2: Post-partum (singleton pregnancy) African-American women are non-lactating, which is defined as bottle-feeding or having weaned their baby from breastfeeding for at least 4 weeks prior to study.
• Group 3: Controls- Healthy non-pregnant African-American women will be race and age-matched to the breast-feeding women in group one. They may not have been lactating or pregnant within the last year.

Exclusion Criteria:

• Subjects with cardiac, hypertensive, vascular, renal (serum creatinine of >1.5), pulmonary, endocrine, musculo-skeletal, hepatic, hematologic or malignant or rheumatologic disease will be excluded from the study.
• Smokers and those with a history of significant alcohol or drug abuse are excluded.
• Baseline hypertension (systolic BP > 160 mm/Hg) or hypotension (systolic BP < 90 mm/Hg).
• Subjects taking any chronic medications except stable doses of thyroid hormone, prenatal, vitamin supplements, or oral contraceptives.
• Those who have received any investigational drug in past 90 days will be excluded from the study.
• Women who are currently pregnant will be excluded from the study. Women who became pregnant by In Vitro Fertilization IVF or any hormonal manipulation (i.e. fertility drugs such as clomid ®) are also excluded, as they may have an altered pre-pregnant hormonal state. All women will have a urine pregnancy test performed at each of the two study visits and must not be pregnant in order to continue in the study. Subjects are not allowed to donate blood between study visits.