During the research and development phase of finasteride, studies were done on experimental animals. Rats, rabbits, and rhesus monkeys were given finasteride to determine its relationship to birth defects, i.e. hypospadias.

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Hypospadias did occur in the male offspring, when pregnant rats were administered doses that were between 5 and 5000 times the amount recommended for men in treating Male Pattern Baldness (1mg/daily). The critical period during which these effects can be induced in male rats was determined to be during the 16th and 17th days of gestation.

In rabbit fetuses which had finasteride directly injected into the uterus from days 6-18 of gestation at doses equivalent to 5000 times the recommended human dosage, no evidence of malformations was observed. This result would be expected, since there was no exposure during the critical period of genital system development in rabbits.

Conceiving a baby while on Propecia

We have all seen the warnings about pregnant women being advised not to handle a broken propecia tablet. In many people's minds, it stands to follow that if they shouldn't handle a broken tablet, surely semen containing finasteride would be dangerous as well. Again, we should always look to the studies to get the facts we need. Scientists intravenously gave 750 times that dosage to Rhesus Monkeys. In fact it was 750 times the highest possible dose a woman could be exposed to through semen from a man taking 1mg per day. Even at this dose, there were no genital abnormalities observed.

Propecia and Genital Development during Pregnancy

In the human embryo, the period of external genitalia development is during the 7th - 9th weeks of gestation. Although the sperm (which can contain finasteride from the man taking Propecia) plays a role in determining the sex of the baby (either Y-bearing or X-bearing), the actual male and female morphological characteristics do not begin to develop until the seventh week of Pregnancy.

Prior to this time, the genital systems of the two sexes are similar, and the initial period of genital development is referred to as the ‘indifferent state of sexual development’. About six weeks after conception, if a Y chromosome is present in the embryo's cells (as it is in normal males), a gene on the chromosome directs the undifferentiated gonads to become testes. If the Y chromosome is not present (as in normal females), the undifferentiated gonads will become ovaries. If the gonads become testes, they begin to produce androgens, primarily testosterone, by about eight weeks after conception. These androgens stimulate development of the one set of the genital ducts into the epididymes, vas deferens, and ejaculatory duct. The presence of androgens also stimulates development of the penis and the scrotum. Hypospadias can result if there is inadequate production of androgens by the fetal testes.

Propecia and Pregnancy - Part 2 Topics: So when is it Safe? | Intercourse During Pregnancy | The Final Word