In addition to the pregnancy risk, there are other consequences.
Sexual promiscuity greatly increases the risk of Sexually Transmitted Infections like Gonnorhea, Genital Herpes, Syphillis, and HIV.
Sexual promiscuity increases the risk of domestic violence. Jealous lovers will either take their rage out on the ex, or whoever stole the ex. Either case can have terrible consequences as "Hell hath no fury like a woman scorned."
The most common reaction to an unplanned pregnancy is sadly abortion. Abortion has many psychological consequences, documented by pro-life groups like Operation Lifesaver. Abortion, and abortifacient contraceptives, also significantly increase risk for breast cancer according to the World Heath Organization.
Finally, sexual promiscuity contributes to the objectification of women. It ingrains the perception (in both parties) that women are something to be owned by the man as an outlet for his sex-drive. This demeans the woman as a person and her role in a proper relationship.
To infants :the result of irresponsible sexual behaviour can be seen in the high number of unwanted babies.In most cases unwanted babies are from teenage pregnancies where the mother feels she can not take care of the baby.And the babies can suffer from malnutrition,illness and die quite early in life