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.
you have to ovulate before you get your period thats just how it works, ovulation is what causes you period as for the other questions, you can get pregnant as soon as a few weeks after...that doesnt mean you will but some times some people can, everyone is different breastfeeding tends to stop ovulation for a while but you can still ovulate as early as someone who isnt breastfeeding...like i said before everyone is different