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.
Eating healthily and doing some gentle exercise will help you to get in shape. This is better than very strict low-calorie diets when you are breastfeeding. You can increase how much you exercise six weeks to eight weeks after giving birth, if you feel up to it (NICE 2010: 15) . Avoid having lots of caffeinated drinks when you're breastfeeding (OTIS 2011) . We don't have a UK guideline for a safe amount of caffeine for breastfeeding mums. In the US, women who are breastfeeding are recommended to have no more than about 200mg of caffeine a day (ACOG 2013, COD 2001) .