Intrauterine growth and adipose tissue development.

Body fat mass (BFM), skinfold thickness (ST), and fat cell weight (FCW) have been studied in 86 newborn infants with different maturity and different intrauterine growth, and in parabiotic twins. Preterm infants (35.5 +/- 0.4 wk) with body weight appropriate for gestational age had lower values of BFM and sum of ST as compared to the control group, without differences in FCW (0.23 +/- 0.03 versus 0.22 +/- 0.02 micrograms). In infants born between 30 and 41 wk of gestation with body weights at birth appropriate for gestational age, ST and BFM progressively increase with gestational age, while the FCW remains constant. These observations suggest that fat mass growth in the last 2 months of fetal life, essentially depends on fat cell replication. In full-term large-for-date babies, bFM resulted significantly greater than in controls both in absolute values (p less than 0.001) and in percentage values of total body weight (p less than 0.001). The FCW in large for date newborns resulted significantly greater than in controls (0.50 +/- 0.06 versus 0.22 +/- 0.2 micrograms, p less than 0.001). In full-term small-for-date newborns BFM, ST, and FCW resulted significantly lower than in controls (p less than 0.001). In full-term newborns with different body weight at birth, fat cell weight was correlated to BFM (r = 0.67; p less than 0.01), to BFM as percentage of body weight (r = 0.67; p less than 0.001) and to ST (r = 0.73; p less than 0.001). In three couples of identical parabiotic twins, the larger baby of every pair showed even greater values of BFM, ST, and FCW and fat cell weight than the respective sibling. These observations suggest that in newborns with different intrauterine growth, a different triglyceride content in single adipocytes largely explains the variations in fat mass development.