The National Standard for Normal Fetal Growth

Background:

• 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 growth.

Objectives:

• To establish a standard for normal fetal growth and size for gestational age in the U.S. population.
• To create an individualized standard for fetal growth potential.
• 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:

• Women will be recruited in the first trimester and followed up through pregnancy.
• Each woman will receive six scheduled ultrasound exams, which will include the following tests:
• Fetal biometry (biological statistics) at all visits.
• Uterine artery and fetal Doppler studies at selected gestational weeks.
• Women will be asked to donate blood samples at enrollment and at follow-up visits at 16-22 weeks, 24-28 weeks, and 34-37 weeks of gestation.
• After delivery, the newborn will be carefully measured to record birthweight, head circumference, and other body measurements.
• Cord blood, plasma, and placenta samples will be collected from selected newborns.
• Post-study evaluations:
• Women who are diagnosed with gestational diabetes during pregnancy will be asked to return for a follow-up visit 6 weeks after delivery.

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.

This study will recruit 2,400 healthy, non-obese, low risk pregnant women from five clinical centers. Approximately 600 women will come from each of the following four self-identified racial ethnicity backgrounds: African American, Asian, Caucasian, and Hispanic. Women will be recruited in the first trimester and followed up through pregnancy. In addition, 600 obese women will also be recruited. Each woman will receive six scheduled ultrasound exams, which include fetal biometry at all visits and uterine artery and fetal Doppler studies at selected gestational weeks. After delivery, neonatal anthropometric measures will be carefully taken. Obstetric and neonatal information will be extracted from medical charts. The National Standard for Normal Fetal Growth will have important implications in clinical practice and research.

• Pregnancy
• Fetal Growth

• Abramowicz JS, Robischon K, Cox C. Incorporating sonographic cheek-to-cheek diameter, biparietal diameter and abdominal circumference improves weight estimation in the macrosomic fetus. Ultrasound Obstet Gynecol. 1997 Jun;9(6):409-13.
• Alexander GR, Himes JH, Kaufman RB, Mor J, Kogan M. A United States national reference for fetal growth. Obstet Gynecol. 1996 Feb;87(2):163-8.
• Altman DG, Chitty LS. Charts of fetal size: 1. Methodology. Br J Obstet Gynaecol. 1994 Jan;101(1):29-34.

• INCLUSION CRITERIA:
• Singleton, viable pregnancy
• 8 plus 0 - 13 plus 6 weeks of gestation
• Maternal age 18 - 40 years
• BMI 19.0 -29.9kg/m(2) for low risk group; BMI 30.0 - 45.0kg/m(2) for obese group
• Firm LMP
• LMP-date and ultrasound date match within 5 days for gestation estimates between 8 weeks + 0 days and 10 weeks + 6 days, 6 days for those between 11 weeks + 0 days and 12 weeks + 6 days, and 7 days for estimates between 13 weeks + 0 days and 13 weeks + 6 days
• No confirmed or suspected fetal congenital structural or chromosomal anomalies
• Expect to deliver at one of the participating hospitals
• No previous participation in the NICHD Fetal Growth Study

EXCLUSION CRITERIA:

• Smoked cigarettes or used illicit drugs in the six months
• Used illicit drugs in the past year
• Having at least 1 alcoholic drink per day
• Conception by ovulation stimulation drugs or assisted reproductive technology
• Chronic hypertension or renal disease under medical supervision
• Asthma requiring weekly medication
• Diabetes mellitus
• Thyroid disease under medical supervision
• Autoimmune disorder (rheumatoid arthritis, lupus, antiphospholipid antibody syndrome,scleroderma)
• Hematologic disorders (chronic anemia, sickle cell disease thrombocytopenia coagulation defects, thrombophilia)
• Cancer
• HIV or AIDS
• Epilepsy or seizure on medication or occurrence within 2 years
• Psychiatric disorder (bipolar disorder, depression, anxiety disorder currently requiring medication)
• Current anorexia nervosa or bulimia
• Previous severe preclampsia, eclampsia, HELLP syndrome
• Previous stillbirth or neonatal death
• Previous very preterm birth (less than 34 weeks)
• Previous low birthweight (less than 2,500 g)
• Previous macrosomia (greater than or equal to 4,500 g)

The following criteria apply only to obese women only:

• Chronic hypertension or high blood pressure requiring two or more medications
• Diabetes while not pregnant
• Chronic renal disease under medical supervision
• Autoimmune disease (rheumatoid arthritis, lupus, antiphospholipid antibody syndrome, scleroderma)
• Psychiatric disorder (bipolar disorder, depression, anxiety disorder currently requiring medication)
• Cancer (currently receiving treatment)
• HIV or AIDS