Multiple births in the United States are rapidly increasing in large part due to assisted reproductive technologies. Recent data indicate that multiple births now comprise 3-4.5% of all births in the United States. Pregnant women are at risk for iron (Fe) deficiency anemia yet there are virtually no data on Fe status in women carrying multiples and current recommendations do not necessitate Fe screening among this high risk group. Maternal anemia is known to increase the risk of adverse birth outcomes including preterm birth and low birth weight. Moreover, the developing brain is increasingly recognized to be susceptible to Fe insufficiency in utero and growing data support that suboptimal Fe stores at birth are associated with long-term irreversible cognitive deficits in the offspring. To address these gaps in knowledge the investigators will monitor weight gain, hematological measures, Fe status indicators and serum hepcidin across pregnancy in approximately 120 women carrying twins and triplets. Determinants of maternal anemia will be identified. Neonatal hematological measures will be assessed in cord blood from each neonate at birth for assessment of hematological measures, Fe status and hepcidin. Determinants of neonatal anemia will be identified. Inflammatory markers will be measured in all blood samples and related to outcomes. Stable iron isotopes will be given to a subset of women to assess maternal Fe absorption and fetal Fe uptake.

Pregnant women (n=100-125) carrying multiples (twins and triplets) will be identified when entering prenatal care. Women will be invited to participate in a longitudinal study of Fe homeostasis across pregnancy and at delivery in the maternal / neonatal dyad. In all maternal and cord blood samples obtained, whole blood will be analyzed for hemoglobin, hematocrit, reticulocyte count, erythrocyte count, mean corpuscular hemoglobin, mean corpuscular Hb concentration, mean corpuscular volume, and red cell distribution width using standard procedures. Circulating Fe status indicators (serum iron, ferritin, C-reactive protein, IL-6, erythropoietin, transferrin receptor and hepcidin) and serum folate and vitamin B12 will be measured. Distributions of each variable will be examined and associations among variables will be explored. Multiple linear regression models will be constructed to examine specific relations between a) determinants of Fe deficiency anemia in the mother; b) Fe status indicators in the mother vs. those in the neonate; c) Fe status indicators in the mother and neonate with placental Fe binding proteins; and d) neonatal Fe status between siblings.

Inclusion Criteria:

• The investigators anticipate that the majority of these women will be recruited early in gestation because many of these pregnancies are a result of assisted reproductive technology.
• Eligible volunteers will be otherwise healthy and have no diagnosed, preexisting medical conditions known to impact iron homeostasis

Exclusion Criteria:

• Hemoglobinopathies,
• Preexisting diabetes,
• Malabsorption diseases

Pregnant women (n = 100-125) carrying multiples (twins, triplets and quadruplets)