Multiple Pregnancy / Twin Pregnancy – Etiology (causes)

• Race: the frequency is highest amongst Negrose. Lowest amongst Mongols and intermediate amongst Caucasians.
• Hereditary: there is hereditary predisposition likely to be more transmitted through the female (maternal side).
• Advancing age of the mother: increased incidence of twining is observed with the advancing age of the mother, the maximum being between the age of 30 – 35 years. The incidence of twins is markedly reduced thereafter.
• Influence of parity: the incidence is increased with increasing parity specially from 5^th gravida onwards.
• Iatrogenic: drugs used for induction of ovulation may produce multiple fetuses to the extent of 20 – 40 % following gonadotrophin therapy, although to a lesser extent (5-6%) following clomiphene citrate.