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 won't have to force the dieting in order to shed those post baby pounds. Breastfeeding naturally burns calories (about 500 a day) and much of the weight will go away naturally as your body shrinks. Even your lactating breasts can add a couple pounds, so don't worry too much about dieting. Losing those 30 pounds will be easier than you think.