The National Standard for Normal Fetal Growth

Summary and aims: Normal fetal growth is a critical component of a healthy pregnancy and the long-term health of the offspring. Pivotal to understanding the dynamics of human fetal growth and to defining normal and abnormal fetal growth is the development of standards for fetal anthropometric parameters measured longitudinally throughout gestation, which, in turn, can be used to develop interval velocity curves and customized for genetic and physiological factors. We propose to conduct a multi-center prospective observational study (1) to establish a standard for normal fetal growth (velocity) and size for gestational age in the U.S. population; (2) to create an individualized standard for fetal growth potential; and (3) to improve accuracy of fetal weight estimation. Eligibility: • Healthy, low-risk pregnant women (both obese and nonobese) between the ages of 18 and 40 from each of the following four self-identified race/ethnicity backgrounds: African American, Asian, Caucasian, and Hispanic. Design: * Observational cohort design where pregnant women are recruited prior to 13 weeks gestation and followed throughout pregnancy and delivery for women having livebirths. * After a sonogram at enrollment (10-13 weeks), women were randomized to receive sonograms according to one of the following four schedules: schedule A: 16, 24, 30, 34, and 38 weeks; schedule B: 18, 26, 31, 35, and 39 weeks; schedule C: 20, 28, 32, 36, and 40 weeks; schedule D: 22, 29, 33, 37, and 41 weeks. * An enrollment interview was followed by depression screening, physical activity, anthropometric assessment and ultrasonology screening for measurement of fetal growth, and at each of the 5 subsequent visits. * Uterine artery and fetal Doppler studies at selected gestational weeks. * Women were asked to provide blood samples at enrollment and at follow-up visits at 16-22 weeks, 24-29 weeks, and 34-37 weeks of gestation. * Neonatal anthropometry completed for all infants within 12-24 hours after birth. * Cord blood, plasma, and placenta samples were collected for a smaller subsample of newborns. * Post-study evaluations: Women who were diagnosed with gestational diabetes during pregnancy were asked to return for a follow-up visit 6 weeks after delivery. Enrollment: Final recruitment included 2,802 women with singleton pregnancies of which 2,334 were healthy, low-risk women with pre-pregnancy body mass indices (BMI) between 19-29.9 kg/m2. The racial/ethnic distribution of participating women were: Caucasians (n=614), African American (n=611), Hispanics (n=649), and Asians (n=460), and reflects natality characteristics of contemporary U.S. births. An additional 468 obese women (BMI 30-44.9 kg/m2) were also recruited. Quality Control: The quality of the ultrasound measures was guaranteed by implementation of: (1) a comprehensive quality control protocol for ante hoc training and credentialing of all site sonographers, developed by the sonology center at Columbia University, and (2) a rigorous protocol for post hoc quality control, whereby a random sample of all scans, stratified by clinical site and visit, was re-measured for accuracy and reliability.