Palmer said what emergency contraceptive pills do is different from what abortion-inducing drugs do.
Sperm can live inside a woman's body for up to 72 hours. Sperm must travel from the vagina, through the cervix, through the uterus, out the fallopian tube, where the sperm meets the egg outside the uterus near the end of the fallopian tube, Palmer said.
The fertilized egg is taken back inside the fallopian tube, and it must travel down the fallopian tube and implant itself into the uterus, she said.
Meaning, a woman doesn't necessarily become immediately pregnant after intercourse.
“If you think about how tiny sperm (are) and how fast they move and the distance that they have to travel, it's not a one-hour kind of ordeal,” Palmer said. “It's a process of many hours that it takes for the sperm to reach its destination and find that egg.”
Ovulation is the time period when an egg is released from the ovaries. During ovulation, the egg cell will either be fertilized by sperm or will dissolve if fertilization does not take place, according to the U.S. National Library of Medicine.
“Why emergency contraception can work is that it can prohibit that ovulation from happening,” Palmer said. “And if you have already ovulated and the sperm get out there, it's probably not going to be effective.”
Emergency contraception cannot dislodge or end a pregnancy. If a woman is pregnant by the time she takes the pills, she will remain pregnant, Palmer said. This is the same for intrauterine devices, Palmer said.
Contributing: Don Mecoy, Business Editor