The Clinical Significance of Deviations in Fetal Growth

Abstract

R. W. Abdul‐Karim, Department of Obstetrics and Gynecology, State University of New York, Upstate Medical Center, Syracuse, N.Y., USA). The clinical significance of deviations in fetal growth.Int J Gynaecol Obstet 13: 257–267, 1975The most commonly employed standard for fetal growth is that of its weight. Such standards have certain drawbacks in that they are based on the weights of preterm liveborn (hence by definition the product of an abnormal pregnancy and not necessarily reflecting the weight of a fetus remaining in utero) and quite frequently are not available for the specific population of a given neonate. The factors that influence fetal weight include paternal size, particularly maternal weight, altitude, fetal sex, multiple pregnancy and race. The construction of intrauterine growth curves must take these into consideration. The importance of considering fetal weight in relation to its gestational age is now evident. Deviations from normal fetal growth are defined rather arbitrarily. The most commonly used limits are those below or above 2 S.D. from the mean or the 10th and 90th percentiles. Such statistical group‐partal, intrapartal and postpartal prognosis varies as to factors accounting for their growth deviation. This in part explains the varied results reported on the follow‐up of these newborns. Fetuses whose birth weight falls below 2 S.D. or the 10th percentile are termed growth retarded. As a group such fetuses have a higher perinatal mortality and morbidity, and their postnatal growth is compromised. However, such newborns do not represent a homogeneous group and their ante‐partal, intrapartal, and postpartal prognosis varies as to whether the infant was the product of a pregnancy complicated by maternal (e.g. toxemias, diabetes) or fetal (e.g. infection, chromosomal abnormalities) disease or was the result of an otherwise uncomplicated pregnancy. In any case the special predilection of growth retarded fetuses to antepartum, intrapartum and neonatal problems warrants intensive assessments during these periods in its development. The growth accelerated (or large for dates) fetus has received less extensive investigation than its counterpart. Such fetuses are often associated with tall heavy mothers or those with certain metabolic diseases (e.g. diabetes, hyperthyroidism). Because of their size they can present obstetrical problems and their postnatal development may be jeopardized. However, there is suggestive evidence that some of the uninjured newborns may have an enhanced postnatal development not only in stature, but mentally as well. It is hoped that the currently available experimental model of growth accelerated fetuses may lead to a better understanding of this aspect of fetal development.