Normal fetal growth is a critical component for a healthy pregnancy and for ensuring the health and well-being of infants throughout childhood and adolescence. 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. Such measures can be used to develop interval velocity curves and customized to assess etiologic determinants such as genetic and physiological factors.
This multicenter, prospective cohort study involves the recruitment and follow-up of (1) 2,400 low-risk, normal weight women divided equally among four self-identified race/ethnicity groups: non-Hispanic White, African American, Hispanic, and Asian, and (2) 450 obese women. Recruitment began in July 2009 at the following clinical sites in the U.S and is expected to continue through January 2013:
The primary goals of this study are threefold: (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.
The secondary objectives include: (1) to construct an individualized standard for fundal height; (2) to collect blood samples for an etiology study of gestational diabetes and related complications and a prediction study of fetal growth restriction and/or overgrowth; (3) to collect placental tissues and cord blood in selected cases and controls for studies on the etiology of idiopathic fetal growth restriction; and (4) to collect dietary intake data to study the association between nutrition and fetal growth.
In 2009 the original study was expanded to include 350 dichorionic twins after receiving additional funds under the American Recovery and Reinvestment Act (ARRA). There are four main research objectives to this component of the study: 1) to describe fetal growth trajectories in twins using two- and selected three-dimensional ultrasound measures; 2) to compare and contrast fetal growth trajectories for twins with the newly established fetal growth standard developed for singletons to determine its applicability for monitoring the growth of twin fetuses and discordant growth of the pair; 3) to estimate the incidence of growth restriction (with SGA as a proxy) in singleton and twin gestations (by zygosity), however, growth restriction may be defined by the new growth standard; and 4) to compare singleton and twin gestations with respect to maternal biomarkers of glucose homeostasis and fetal growth and maternal nutritional status using banked biospecimens to determine if the biomarkers ranges established for singletons are applicable to twin gestations. Recruitment began in February 2012 and is expected to continue through January 2013.
The NICHD Fetal Growth Study is designated as one of the NIH ARRA Signature Projects.
Germaine Louis, Ph.D., M.S.
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