A reader writes:
As a Catholic, you should know that while the IUD may be seen as a viable alternative to the pill, Catholic women who use contraception would probably see the IUD as more problematic than the pill for one reason: an IUD does not prevent conception. With an IUD, conception occurs, but the IUD makes for a more "hostile" environment for the embryo to implant. Since implantation does not occur, the embryo is "discarded" with the woman's next period.
Now, to be fair, conception *can* occur when a woman is on the pill, but it is much less likely, since the goal of the pill is to prevent ovulation. Obviously, many women have gotten pregnant on the pill. But the difference for a Catholic would be that on the pill, ovulation is prevented, so most of the time, conception does not occur. With an IUD, conception can occur at any time, and then you're dealing with an entirely different moral situation for a Catholic.
Another is more direct:
The IUD is a form of abortion.
I have moral uneasiness about the IUD. I am definitely pro-choice, but not really for myself (maybe at a younger age, but not now – age 33, mom to a 6-month old). I know the latest versions of IUDs are pretty safe, but it prevents implantation, not fertilization. I feel weird about allowing eggs to be fertilized and then preventing them from implanting. I guess I believe in souls and the sanctity of life, so I don’t know that I want to repeatedly create life (even if only a few cells) only to never give it a chance.