EFFECT OF SURGICALLY INDUCED ENDOMETRIOSIS ON PREGNANCY AND EFFECT OFPREGNANCY AND LACTATION ON ENDOMETRIOSIS IN MICE

Endometriosis, a disease of women and nonhuman primates in which endom etrial tissue grows outside the uterus, can be mimicked surgically in rats and mice, The disease is related to infertility in women, and sur gical induction of endometriotic lesions reduces fertility in rats acc ording to some studies. Conversely, pregnancy appears to have a benefi cial effect on endometriosis in women and some rat studies, Our object ive was to evaluate a new mouse model of surgically induced endometrio sis with respect to the effects of pregnancy on endometriosis and the effects of endometriosis on pregnancy, Female B6C3F1 mice were divided into four groups. Those in Group A and B underwent induction surgery for endometriosis and hemi-ovariectomy, those in Group C underwent sha m surgery and hemi-ovariectomy, and animals in Group D received no sur gery at all, Three weeks later, Group A, C, and D were bred. Eighteen days later one half of the dams in Groups A, B, and C only were sacrif iced, and evaluations included endometriotic lesion diameter, number o f pups, fetal weight, and various organ weights, The remaining darns d elivered, and, 18 days after parturition, dams and pups were sacrifice d, Evaluations included gestation length and those listed above, Endom etriotic lesion diameter was significantly reduced in pregnant animals when compared with nonpregnant controls, but the reduction was not a full regression, Lactation returned the mean lesion diameter to prepre gnancy dimensions, When effects of endometriosis on pregnancy were eva luated, no effects on the litter size, pup weight, or gestation length were found, but trends toward increased resorptions and malformations were evident. Thus, in the mouse model of induced endometriosis, preg nancy produced a significant reduction in endometriotic lesion diamete r while fertility was largely unaffected by the surgically induced end ometriosis. The mouse model of endometriosis thus appears more resista nt than the rat model to effects of endometriosis on fertility.