Effect fo potential placental surface area reduction on fetal growth.

This investigation was undertaken to study the effect of reduction of placental surface area on fetal growth. The right horn of the bicornuate uterus was removed in nonpregnant ewes, the ewes were bred and 11 out of 15 became pregnant. Near term, under experimental conditions, maternal and fetal blood gases, pH, uterine and umbilical blood flows were measured or calculated. Fetal, placental membrane, uterine, and cotyledonary weights and number of cotyledons were recorded. The experimental hemi-hysterectomized group was compared to a control group of 14. Results show that: (1) weight per cotyledon was significantly greater (p less than 0.01) in the hemi-hysterectomized series than in the controls, (2) loss of a significant number of placentation sites was compatible with the production of term-sized fetuses, (3) since the difference between the number of cotyledons in the hemihysterectomized and control groups is significantly less than the number of implantation sites removed, the efficiency of implantation is improved, and (4) there were no changes in blood flows, PO2, PCO2, and fetal oxygen consumption.