Seems this is an off-label indication, and doctors use it based on experience
As for your question about decreasing chances to get
pregnant, I have no idea about that, but I can tell you that seroquel is in category C of risk
for pregnant women. As per FDA, this means:
Either studies in animals have revealed adverse effects on the fetus (teratogenic or embryocidal or other) and there are no controlled studies in women, or studies in women and animals are not available.