Single placentas in the rhesus monkey.

Abstract

Data from 121 consecutive pregnancies conceived and delivered in one accumulated Macaca mulatta colony were examined as to the presence of a single or double disc placenta. Neither the occurrence of implantation bleeding, nor the season of the year, nor the sex of the conceptus affected the incidence of 22 % single placenta pregnancies. A nonsex-linked genetic etiology consistent with a simple Mendelian model is developed.