A patient delivers a twin gestation in which one infant has blood group O and one has blood group B. The patient and her husband are both type O. Discordant blood types is explained by
The clinical Scenario describes suferfecundation.
It involves fertilization of one ovum that splits into two during the same menstrual cycle.
It involves fertilization of two ova within same menstrual cycle, but not at the same coitus.
It involves fertilization of two ova separated in time by an interval as long as or longer than a menstrual cycle.
This does not occur spontaneously in humans.