American Journal of Obstetrics and Gynecology study on rape-related pregnancy
1996 study
http://www.ajog.org/article/S0002-9378%2896%2970141-2/abstract
RESULTS: The national rape-related pregnancy rate is 5.0% per rape among victims of reproductive age (aged 12 to 45); among adult women an estimated 32,101 pregnancies result from rape each year. Among 34 cases of rape-related pregnancy, the majority occurred among adolescents and resulted from assault by a known, often related perpetrator. Only 11.7% of these victims received immediate medical attention after the assault, and 47.1% received no medical attention related to the rape. A total 32.4% of these victims did not discover they were pregnant until they had already entered the second trimester; 32.2% opted to keep the infant whereas 50% underwent abortion and 5.9% placed the infant for adoption; an additional 11.8% had spontaneous abortion. CONCLUSIONS: Rape-related pregnancy occurs with significant frequency. It is a cause of many unwanted pregnancies and is closely linked with family and domestic violence.
edit: added BOLD