effect of uterine space and fetal sex on conceptus development and in vitro release of progesterone and estrone from regions of the porcine placenta throughout gestation intact n 17 and unilaterally hysterectomizedovariectomized uhox n 19 gilts were used to study conceptus development and the steroidogenic capability of three regions of the porcine placenta under normal and crowded intrauterine conditions gilts were hysterectomized on either days 30 50 70 or 90 of gestation placentas were combined according to the sex of the fetus associated with the placental unit except at day 30 when all were combined placentas were cut into three regions middle inner and polar placental tissues were incubated for 0 1 5 and 3 hr and concentrations of progesterone p4 and estrone e1 in the incubation medium were determined fetal survival rate was greater p 001 005 and 0001 at days 50 70 and 90 respectively in intact than in uhox gilts placental length and weight fetal length and weight and allantoic fluid volume were greater p 005 0001 005 and 0001 respectively in intact than in uhox gilts p4 concentration was lower p 0001 0002 and 0001 at days 50 70 and 90 respectively in the incubation medium of polar region placenta compared with the other regions the release of p4 was greater p 0005 from the placentas of intact versus uhox gilts at day 90 but was not different at days 30 50 or 70 the sex of the fetus did not affect placental p4 release the region of the placenta affected e1 release at day 30 p 001 greater in polar section and day 50 p 006 less in polar section there was no effect of uterine status on e1 releaseabstract truncated at 250 words