Sarah Varney:
So let’s take a step back and start with how contraception actually works. In the U.S., about 25 percent of women between the ages of 15 and 44 who use contraception take the birth control pill. The pill is available in different combinations of hormones, but they work the same way, by preventing a woman’s ovaries from releasing an egg each month.
The pill also thickens her cervical mucus, essentially creating a barrier so that sperm are blocked from entering the uterus. The hormones in the pill can also thin the uterine lining, making it less likely that a fertilized egg will implant, which is when pregnancy begins. Accounting for missed or forgotten pills, the birth control pill is about 93 percent effective.
Then, there are IUDs, T-shaped devices inserted in the uterus that prevent fertilization. The hormonal IUD thickens mucus found in the cervix, and the copper IUD disrupts the sperm’s movement. IUDs are one of the most effective forms of pregnancy prevention, about 99 percent. They can remain in place for three to 10 years, and like all hormonal birth control, once removed, do not affect a woman’s future fertility.
