We’ve been talking here about how long it will take for a woman to get pregnant after stopping birth control. Last week, we looked at how the Pill affects women who are trying to conceive. Today, we’ll take a peek at IUDs and fertility.
There are two types of IUDs in North American use currently – the older Paragard Copper T and the newer synthetic progesterone-releasing Mirena. Historically, these IUDs were placed in women who had already had a child. Then the FDA approved the Copper T for use in women who had not had a child, as long as they were at least 16 years of age. The Mirena is commonly used “off label” in women who have never had a child, but it was approved by the FDA for those with prior pregnancies.
So are there any differences in the return to fertility between the two types of IUDs? Generally, there is no statistical difference in pregnancy rates after the removal of either type of IUD. One particularly good study randomly assigned women to one of the two types of IUD, then followed the time to pregnancy after the IUDs were removed. In this study, time to conception after Copper T removal was 3 months and 4 months for the Mirena (Belhadj, 1986). It is important to note that the women in these studies had had prior pregnancies, thus known fertility.
In a retrospective study of 2269 women (Hassan, 2004), 82 women used a non-hormonal IUD and 13 used the Mirena. Compared to women using condoms, the time to pregnancy in non-hormonal IUD users was twice as long. The Mirena users had the same time to pregnancy (about 4 months) as condom users.
What about pregnancy rates for women who have not yet conceived? In a retrospective study of former Copper T users, there was no difference in return to fertility between never pregnant, and previously pregnant women (Hubacher, 2001). The usual cause of infertility from IUD use is scarring in the fallopian tubes from chlamydia infections. In this study, only the presence of blood antibodies to chlamydia was associated with infertility – not Copper T use. In a more recent study (Merki-Feld, 2007), prior chlamydia infections in Copper T users were linked to scarring in the fallopian tubes. This linkage was not seen in users of birth control pills nor condoms. Thus, if you want to get pregnant after your IUD is removed, be sure to protect yourself from gonorrhea and chlamydia by monogamy, condom use or frequent STD screenings. Better yet, consider another birth control method if you are likely to have non-condom sex with new partners.