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Factors Predicting Ante- and Postnatal Growth« Back to Volume 24, Issue 2, November 2008 - Table of Contents In an attempt to better understand factors which contribute to both antenatal and postnatal growth, a series of conditional analyses were performed on data collected prospectively from 1218 mother and infant pairs. The study subjects had to be Caucasian, have a prenatal visit before 20 weeks, and had to demonstrate a structurally normal single fetus which was carried to term. Maternal steroid use or thrombotic disorders disqualified the pairs. At the first prenatal visit maternal height was measured as well as paternal height when available. Maternal weight was measured and the history was taken with regard to tobacco use. Socioeconomic status was determined from information regarding education, marital status, occupation, partner’s occupation, and social class. Assignment was made using the classification system of the UK Office of Population, Census, and Surveys. Placental weight was recorded after the membranes were trimmed. Birth weight was measured using self-calibrating scales, length by infantometer, and head circumference with a metal tape. In addition, skin fold measurements were made at the triceps, subscapular, and quadriceps areas. These measurements were repeated at 6 months of infant age. Feeding practices were noted at birth and reassessed at 3 months. These were classified as totally breast fed, mixed, or totally bottle fed. The cohort of women in this study was not different anthropometrically from the UK population and social class distribution was also representative. Non-smokers comprised 71% of the cohort. Placental weight was shown to be related to birth weight, birth length, and head circumference. Factors determining placental weight, when birth weight was excluded, were gestational age at delivery, maternal height, weight at first prenatal visit, and paternal height. One factor—increasing parity—had a negative effect. These factors explained 7% of the variance in placental weight. When the analysis was redone including birth weight, length of gestation, and smoking during pregnancy, these also influenced placental weight in a positive manner. Female gender was associated with reduced placental weight. These factors explained 40% of the variance in placental weight. Placental weight, parity, maternal weight at first prenatal visit, and gender of the infant did not influence weight, length, or head circumference at 6 months of age. Weight at 6 months was influenced by maternal and to a lesser extent paternal height. Smoking was associated with a relatively heavier infant at 6 months and lower socioeconomic status had an additional effect as did breast-feeding. Duration of pregnancy was also an important factor. Length SDS at 6 months was influenced by maternal and paternal height. Smoking had no effect on length at 6 months. Head circumference at 6 months was influenced by maternal weight, height, duration or pregnancy, and maternal smoking whereas breast-feeding at 6 months was associated with a reduction in head circumference SDS. These data demonstrate an important impact of maternal and paternal stature on the size of the infant at 6 months. Parity, placental weight, and birth weight, although important to the size of the infant at birth, have little effect on growth during the first 6 months. The effect of parity is mediated by determination of size of the infant at birth and this is mostly mediated by placental weight. The findings demonstrated that small and large babies have small and large placentas respectively. The authors pointed out that the factors that might be modified to determine placental weight and therefore size at birth are rather limited, the most important being smoking. Smoking during pregnancy is associated with a lower birth weight, shorter length and reduced head circumference. But there is compensation in growth during the first 6 months of postnatal life. They also pointed out that of all 3 anthropometric measures at 6 months, maternal and paternal stature impacted the most with maternal height having more effect on weight and head circumference. They concluded that the data highlight the importance of factors such as smoking and parity that can be manipulated by public health education and others such as gestational length that can be hopefully manipulated by careful prenatal care and attendance at prenatal clinics. Editor’s CommentThis interesting manuscript attempts to characterize factors that influence growth during infancy—and particularly at an age which is effected primarily by nutrition and for the most part is growth hormone independent. It is important to note that all of these data were collected from uncomplicated pregnancies. However, this large cohort is socioeconomically and anthropometrically representative of the UK population. Thus, the information is of extreme importance in obtaining a better understanding of how infants grow and which factors may be important. It is also important for pediatric endocrinologists to better understand the factors that may be contributing to growth failure in infants referred to their practices. William L. Clarke, MD
« Back to Volume 24, Issue 2, November 2008 - Table of Contents
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Volume 26 Number 1
September 2010
www.GGHjournal.com
ISSN 1932-9032
