Intrauterine growth of chronically instrumented rhesus monkey fetuses

The effect of surgical and experimental manipulations on intrauterine growth of the fetus was investigated in 61 rhesus monkey fetuses in which chronic preparations were attempted. The surgical procedure consisted of hysterotomy and insertion of vascular catheters and included unilateral ligation of the fetal carotid artery. The mother was kept in a restraining chair after the operation for the duration of the preparation (0 to 39 days). Thirty-four fetuses who died within 48 hours after operation served as the control group for the growth parameters. The remaining fetuses that survived 7 days or more after the operation were included in the experimental group. Body weight, crown-rump length, crown-heel length, and foot length of the fetus and placental weight were measured at the termination of the preparation. There were significant linear correlations between all parameters and gestational age. Comparison between the control and experimental groups revealed that none of the parameters from the experimental group differed significantly from those of the control group. No relationships were found between the duration of the preparation and any of the parameters. Total brain weights from 19 fetuses exhibited a significant increase with gestational age and these values were within the normal range reported previously. There were no significant differences in weight between right and left cerebral hemispheres. No evidence of unequal blood flow to the cerebral hemispheres was found with the radioactive microsphere technique. The data suggest that the surgery performed on both the mother and the fetus and prolonged maternal restraint did not alter intrauterine fetal development.