Effects of the spermicide nonoxynol-9 on the pregnant uterus and the conceptus of rat.

In a series of experiments the embryotoxic potential of nonoxynol-9 (N-9) was investigated in adult female rats given a single per vaginam application of 5 mg/100 g (0.1 ml/100 g) of this spermicide on day 3 (pre-implantation period) or 7 (postimplantation period) of gestation. Control rats were given physiologic saline (0.1 ml/100 g) intravaginally. The vulvar labia were apposed for 24 h by metallic clips to prevent leakage of the solution. Groups of dams treated on pregnancy days 3 and 7 were killed by CO2 inhalation on gestational days 6, 9, 12 and 15, and 8, 9, 10, 12 and 15, resorption and total resorption of the conceptus, embryonal and placental resorption and total resorption of the conceptus, embryonal and placental necrosis, placentitis, endometritis, multicystic endometrium, and diffuse or segmental dilatation of the uterine horns. Generally, the incidence of these lesions varied with the length of time after N-9 was administered and it was consistently higher in the females treated on pregnancy day 3 than in those treated on day 7. Acute vaginitis waned with time after the application of N-9. It was concluded that under the conditions of this study, N-9 is embryocidal/fetocidal in the rat if administered during the first week of gestation. The impairment of embryonal/fetal development was attributed to the N-9-induced changes in the endometrium, the placenta and/or the embryo.