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Fetal growth: boys before girls
F de Zegher1, H Devlieger, R Eeckels
1Department of Pediatrics, University of Leuven, Belgium.
Insights
Male fetuses grow earlier and faster than females, impacting developmental timing. This early fetal growth difference may explain gender-based variations in fetal programming sensitivity.
Area of Science:
- Reproductive biology
- Developmental biology
- Pediatrics
Background:
- Boys are typically heavier than girls at term birth.
- Androgen action is implicated in fetal growth differences, but its precise timing is unclear.
Purpose of the Study:
- To investigate the temporal dynamics of fetal growth differences between male and female fetuses.
- To determine if gender influences the timing of fetal growth, not just the rate.
Main Methods:
- Analysis of gestational age and birth weight data for 281,894 newborns (boys and girls).
- Statistical examination of the relationship between gender, birth weight, and gestational age.
Main Results:
- Boys were consistently younger than girls for a given birth weight (p < 0.001).
- This gestational age difference was most significant in lower birth weight categories.
- Fetal growth gender disparity is more pronounced earlier in gestation than near term.
Conclusions:
- Male fetuses exhibit accelerated growth, starting earlier in gestation compared to female fetuses.
- Differential timing of fetal development may contribute to gender-specific vulnerabilities in fetal programming.
- Understanding these growth patterns is crucial for deciphering gender differences in developmental trajectories.
Abstract:
At term birth, boys are heavier than girls. This difference is thought to be generated in part by androgen action; its time course has not been deciphered. Androgen action may not only increase weight gain, but may also alter its time course. We have tested this hypothesis by examining the difference in gestational age of 281,894 boys and girls with weights between 500-4,749 g. The age at which children are born with a given weight was found to depend on gender: boys were consistently younger than girls (p < 0.001), the age difference being most pronounced in the lower birth weight classes. Thus, the gender difference in fetal growth appears to be rather pronounced before the third trimester and relatively less marked towards term. In conclusion, the male conceptus seems to grow not only more, but also earlier than the female. Hence, some critical time windows of development may be slightly different in boys and girls, and this phenomenon may be one of the bases for gender differences in the sensitivity to fetal programming. Copyrightz1999S. KargerAG,Basel