Cellular growth of the placenta in twin pregnancy late in gestation.

In order to establish the pattern of cellular growth in placentae from human twin pregnancy, the total placental concentrations of deoxyribonucleic acid (DNA) and protein were determined. Twin placentae from 31 to 40 weeks' gestation were analysed from 40 pregnancies whose precise gestational ages were known. The study has shown that nuclear multiplication continues until placental growth in weight itself comes to an end. Increase in placental weight was caused by cellular hyperplasia without hypertrophy.