Objective: To study gender differences in fat store in human newborns and their relation to duration of gestation and maternal weight gain.
Methods: The ratios subscapular skinfold thickness/body weight (SST/BW) and tricipital skinfold thickness/body weight (TST/BW) were calculated in a sample of 13609 premature and term neonates from the maternity hospital of Clamart, Hauts-de-Seine, France.
Results: Whereas BW, SST and TST increased with gestational age, SST/BW and TST/BW ratios decreased regularly, in males as in females. This result reflects a progressive reduction of subcutaneous fat store per body weight unit as the duration of gestation increases. Males had smaller values of SST/BW and TST/BW ratios than females whatever the gestational age. Increasing maternal weight gain during the third gestational trimester did not improve the subcutaneous fatness per body weight unit of the newborn. Earlier amount of maternal weight gain had an effect on the TST/BW index exclusively in females.
Conclusions: In newborns, a gender difference was observed in the ratio of subcutaneous fat per unit of body weight; this ratio is lower in males than in females. This result argues for a gender difference in mobilization of fat store to ensure normal growth in the last weeks of pregnancy: males lose more fat but gain more weight than females in this period. Late maternal weight gain does not affect the proportion of subcutaneous fatness by body weight unit in both genders.