When couples use natural family planning, they have sexual intercourse only on days when the woman is least likely to get pregnant. They watch the calendar and use clues from her body to know when she is releasing an egg (ovulating). Then they abstain from sex during the period when she is fertile - usually about seven to 10 days of the month.

This is a difficult way to prevent pregnancy and means taking the woman's temperature each morning before getting out of bed, keeping track of changes in her vaginal discharge, and abstaining from sex seven to 10 days each month. Teen girls often have irregular menstrual cycles, so it's much harder to predict when they'll ovulate. Plus, it offers zero protection against sexually transmitted diseases.

Natural family planning works best for adult women in committed relationships, who have regular cycles, and can handle dealing with an unplanned pregnancy. Typically, with mistakes and all, this method works about 75 percent of the time. When used perfectly, it's 91 percent effective.

For more information, you can call the Sex Information Line at 1-888-30-SX-ASK (307-9275).