My wife seemed on-board for a while, but her OB-GYN convinced her otherwise. She convinced her that NFP was not reliable and that the pill is not a bad thing at all.
I think the first thing you may want to consider is finding a new OB-GYN who isn’t lying to her. You can find this information on your own, but this is directly from the Physicians Desk Reference.
Ethinyl estradiol and norgestimate contains a combination of female hormones that prevent ovulation (the release of an egg from an ovary). This medication also causes changes in your cervical mucus and uterine lining, making it harder for sperm to reach the uterus and harder for a fertilized egg to attach to the uterus.
What this means is that the birth control pill (insert which one you are using here) makes it harder for a fertilized egg to attach and thus one method of prevention is abortion. If you are pro-life and understand that a human life begins at conception, you must then realize that the birth control pill causes abortions as one method of prevention.
I understand that you may realize this, but maybe she does not believe your source. Simply look at the label on your birth control, it will be right there because they cannot hide it, they can only ignore mentioning it on their commercials.
In regards to effectiveness, NFP is as effective as you make it. If you understand the rules and you break them, than the fault is not with the method. It would be like having sex without a condom and blaming the condom for the pregnancy. That being said, of course NFP is not 100% effective, as a condom, BCP and surgical sterilization are not. Anytime you have sex, you have a chance of getting pregnant (this is the natural result of sex in fact). The only 100% effective way of avoiding pregnancy is by not having sex and no matter which method of birth control you use, you have to understand this to be true.
Morally, abstaining is not similar to contraception and using NFP is not a moral sin (as one poster mentioned). Anyone who believes the Catholic Church teaches that using NFP for spacing children is a mortal sin should re-read the CCC (2370 in particular). While I would agree that you should have a valid reason to avoid pregnancy, spacing your children is one of them as stated in the CCC. If you are called to marriage, you are called to have children and so permanent abstinence is also not an option.
As some have posted previously, this temporary abstinence can be a building experience. It is only when you look at it like “we can’t have sex tonight” that you start to see NFP as a negative. There are many statistics to show that NFP practicing couples have success in spacing children and more importantly staying married. In a time when divorce rates are at incredible highs, NFP practicing families are much more stable. I would recommend focusing on building your relationship through NFP as well as mentioning the health reasons for not using the BCP. NFP is the reason I have come to the Church in recent years and it has done amazing things in my relationship with my wife.
I will pray that you can communicate these things in a way to not create separation between you and your wife. I will also pray that the message will be heard because it is of monumental importance. I think the health reasons are important and the moral implications behind using the BCP are of even greater importance, but often overlooked are the truths to the impact practicing NFP can have on your marriage if you allow it. I would question why anyone would use the BCP or the barrier method when the wonderful gifts God has given us like the woman’s natural cycle and using NFP are available.
In using a barrier method or contraception, it seems to me that one is more interested in giving in to their desires than to actually focusing on loving your spouse. If you can’t wait until an infertile period to have sex, is the act truly a giving of yourself to your spouse or is it the need to fulfill a human desire of the flesh? I do not intend to offend anyone, but just provide a simple reflection into your relationship. In the end, it comes down to can you say no instead of sterilizing yourself so you don’t have to. If you can’t say no, what good is your yes.