Lack of harmful effects from simulated dives in pregnant sheep.

The purpose of the study was to determine if a near-maximum exposure to air at increased atmospheric pressure causes gross fetal malformations, decreased birth weight, or death when administered to pregnant sheep during peak development of the embryo. Twenty-eight timed-pregnant sheep were alternately assigned to a series of 25- or 30-minute exposures at either 4.6 atmospheres absolute or surface pressure between days 12 and 40 of gestation. About day 130 of pregnancy, 11 experimental and eight control fetuses were recovered, weighed, measured, fixed, and examined for defects. No major structural malformations were present. One minor variation, an undescended testis, occurred in a treated fetus. The results indicate that a series of short, marginally tolerated "dives" by pregnant sheep during peak development does not affect fetal health or survival.