Pregnancy rate

Three studies examined the effects of endosulfan exposure on reproductive performance in rats. Consumption of estimated doses of endosulfan of up to 9 and 8 mg/kg/day by male and female rats, respectively, for 2 weeks prior to mating and continued consumption throughout gestation resulted in no adverse effect on mating performance, pregnancy rate, or gestation (Hoechst 1982). This study is limited in that the actual intake of test material was quantified only during the first 2 weeks of exposure, and a relatively small number of animals was used. Similarly, consumption of 5 mg/kg/day by male rats and... 

The accidental pregnancy rate for women who do not use any form of contraception is unknown. Therefore, it is difficult to determine the true efficacy of contraceptives in preventing unwanted pregnancy. Table 45-1 shows the percentage of women who experience unintended pregnancy within 1 year of use of a contraceptive.7... 

An adverse effect of lead on pregnancy rate has been noted in some animal studies (Kennedy et al. 1975). Acute-duration gavage administration of 390 mg lead/kg/day as lead acetate to rats resulted in a sharp decrease in pregnancy rates. This effect was not noted at 39 mg lead/kg/day. The study limitations include a lack of measurement of blood lead levels and lack of statistical analysis of pregnancy incidence. A decrease in the number of implantations was noted in untreated female mice that were mated to males that had been treated with 141 mg/kg/day lead chloride in the drinking water for 3 months... 

The abstinence (rhythm) method is not well accepted, as it is associated with relatively high pregnancy rates and necessitates avoidance of intercourse for several days in each cycle. 

The female condom (Reality) covers the labia as well as the cervix, thus it may be more effective than the male condom in preventing transmission of STDs. However, the pregnancy rate is reported to be 21% in the first year of use. 

Not only is it difficult to detect effects on male fertility because of group-size considerations, effects on male fertility mediated by decreased sperm production are also difficult to detect because of the normally huge excess of sperm included in a rat ejaculate. Sperm production can be decreased by up to 90% without effect on fertility (either pregnancy rate or litter size) in the rat. This is not the case for men, so the sperm excess in the rat represents a serious flaw in the rat model (see Working, 1988). To address this deficiency and improve the sensitivity of the model, it is advisable to determine the effects of the test agent on testes weights, testicular spermatid counts, and histopathology of the testes (preferably plastic sections) in the male fertility study and/or the 14-week toxicity study. In some cases, these parameters may be more predictive of possible effects on male fertility in humans than the fertility rate in rats. 

Despite the fact that DCE is not spermicidal, a DCE gel composition without N9 showed a pregnancy rate almost equivalent to the commercial control (with 4% N9). Furthermore, the DCE gel with only 2% N9 had the lowest pregnancy rate (and mean number of implantation sites). 

In a preliminary in vivo animal study, DCE gel, without pharmaceutical active, reduced pregnancy rates to the same degree as a leading commercial product containing 4% N9. The addition of 2% N9 to DCE gel induced a significantly lower embryo implantation rate than the commercial product containing 4% N9. 

With respect to fertility, organic animal husbandry practices seem to be beneficial to the pregnancy rate after the first insemination and to the incidence of crippled animals (Snijders and Baars 1995). 

Studies examining reproductive effects in animals are invariably lengthy and initially catch all. An effect of reduced pregnancy rates in treated females having mated with treated males may be the result of a number of factors that would have to be examined methodically. 

A slight decrease in pregnancy rate was observed in female rats exposed to 130mg manganese/kg body weight per day as manganese tetroxide in the diet for 90-100 days before breeding. ... 

Annual and 5-Year Cumulative Pregnancy Rates Per 100 Levonorgestrel Implant Users by Weight ... 

Accidental pregnancy rate during a 1-year period. 

Pregnancy rate is not normally an indicator of an effect of the test substance, but where there is an increase in preimplantation loss then some animals may not be pregnant due to 100% preimplantation loss. This is of particular importance where dosing... 

Key to FDA use in pregnancy ratings. Physicians Desk Reference, 49th ed. (1995) Montvale, NJ Medical Economics Data Production Co., p. 2797. 

As part of an intermediate duration study, in which rats were exposed to 500 ppm isophorone in air, Dutertre-Catella (1976) mated exposed males with exposed females, control males with exposed females, exposed males with control females, and control males with control females after 3 months of exposure. Exposure of females continued throughout gestation, and they were allowed to deliver. No differences in pregnancy rate or litter size and no abnormalities in pups were found. The pups were not examined for internal malformations therefore, this study was inadequate to determine developmental effects of isophorone. 

As discussed above in Section 2.2.1.5, no differences in pregnancy rate or litter size were observed in rats exposed to isophorone in air at 500 ppm for 3 months before mating (Dutertre-Catella 1976). Since this study did not examine other parameters of reproductive toxicity, 500 ppm cannot be considered a NOAEL for reproductive effects. 

In 71 women undergoing in vitro fertilization and embryo transfer using recombinant human follicle-stimulating hormone in doses sufficient to attain a pregnancy rate of 24% (10), the main adverse effect was mild pain at the site of injection (less than 20% of patients) but there were two cases of ovarian hyperstimulation syndrome. In less than 10% of patients, redness, swelling, or bruising was seen and one patient developed headache. 

Up to 10% of pregnancies among users of progestogen-only contraceptives implant outside the uterus this is not greatly different to the ectopic pregnancy rate in unprotected women, but it is much higher than among users of adequate combined oral contraception (292). The reasons... 

Because the pregnancy rate among users of Norplant is quite low, the rate of ectopic pregnancy is also very low. There is no evidence that infants conceived during Norplant use are at higher risk of birth defects. 

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