Relationship between fetal weight, placental growth and litter size in mice from mid- to late-gestation

In mammals, the placenta, which consists of maternal and fetal components, is important in fetal development because it supplies the fetus with the nourishment it needs. We investigated the effects of placental growth and litter size on mouse fetal weights from mid- to late-gestation. The mean weight of male fetuses at 13.5 days post coitum (dpc) was larger than that of females. Although there was a significant correlation between fetal and placental weights in both males and females during mid-gestation (P < 0.05), there was no correlation during late-gestation. However, a significant correlation was observed between litter size and fetal weights in both males and females at 17.5 dpc (P < 0.05). These findings suggest that fetal weight is regulated by placental growth during mid-gestation, while the effects of litter size are more prominent towards late-gestation.