Ultrasound measurements at each follow-up visit included standard fetal biometrics ((BPD, HC, AC, FL) and the following volumes in the singleton study if they were able to be obtained: 1st trimester: fetus and gestational sac; 2nd and 3rd trimesters: head, cerebellum, face, chest, heart, abdomen, pelvis, arm and thigh. In twins, the volumes collected were 1st trimester: fetus and gestational sac and in the 2nd and 3rd trimesters the thigh. In addition to ultrasound, this study recorded maternal anthropometrics and a brief interview to capture changes in health status, stress and depression, and physical activity at each follow-up visit. Blood draws at baseline and at targeted gestational ages were obtained for the eventual identification of biomarkers indicative of fetal growth were collected. After delivery, neonatal anthropometric measures were assessed, placental biospecimens were collected, and select information about the obstetrical course and newborn status were abstracted from medical charts.