Author(s): WITOLD MALINOWSKI1, DOROTA ?WIEK2
There is a common belief that during the breastfeeding a woman can not get pregnant becauselactation stops the occurrence of ovulation. Also, some studies have shown that during lac-tation there are more than 10. fold greater chance of conceiving not only dizygotic but alsomonozygotic twins. In case of dizygotic pregnancy it is probably caused by a sudden increasein the concentration of FSH in the serum upon the resumption of the menstrual cycle. Ho-wever, the mechanism responsible for the increase in the proportion of monozygotic twinpregnancies that arise as a result of secondary division of the originally single zygote into twoseparate and genetically identical embryonic structures has not been elucidated yet.