The genotype of the mother and the fetus influences the efficacy of a teratogen. For example, genotype determines the prevalence of cleft palate in inbred strains of mice whose mothers are administered cortisol during pregnancy.
Most women will not start ovulating in the first six weeks after giving birth.1 Breastfeeding typically delays the onset of ovulation.2 Depending on the intensity of breastfeeding, it can be several months or over a year before you regain your fertility.
If you're breastfeeding you may not see your period for some time, since prolactin â the hormone responsible for breast milk production â also suppresses ovulation. Many moms don't have a period for months (or at all) while breastfeeding. But lack of a period doesn't mean you can't get pregnant.