Intensely lactating mothers do not generally conceive due to

The correct option is A Suppression of gonadotropins
During intense lactation, up to 6 months to 2 years, there is suppression of gonadotropins (prolactin is high which inhibits FSH and LH) which inhibits ovulation and thus, the women lack menstrual cycle during this period. Thus, coitus during this time will not lead to conception. This is a natural method of conception called as lactational amenorrhea.

So, the correct answer is option A.