Multiple births in drug-addicted women

Two sets of twins and two sets of triplets were delivered in a group of 126 pregnant drug addicts. The over-all multiple-birth incidence of 1:32 is three times more prevalent than that found in the general population. Three of the four multiple births were dizygotic. The mothers with the dizygotic multiple births were on moderate to elevated levels of heroin or methadone at the time of conception. Mechanisms are presented to help explain why narcotics may cause supraovulation and multiple births.