I have been saving and avoiding this particular topic to write about for almost a year now, hesitant to make any comments on this particular subject. Sex, birth control, and all that goes with it is not my favorite topic to write about. But I also think it is important to know why Catholics do not believe in hormonal birth control and barrier methods to avoid pregnancy.
Hormonal birth control can be a pill, a patch, a shot, an IUD that effects a woman's natural hormonal cycle to prevent a pregnancy. Barrier methods of birth control are things that literally create a barrier between the potential fertilization, such as condoms or diaphrams. To avoid pregnancy means just that; if a thirteen year old girl is using birth control for a different purpose, the Church has no problem with that medical decision.
So why is the Pope in your medicine cabinet or bedroom telling you what you can and cannot use? The Church teaches that once you are married (and now sexually active) part of your duties as a married couple is to accept God's sovereignty into their lives and be open to children, whenever God decides to bless you with them. Essentially, we are to leave science out of the bedroom, but it is nothing but science that allows us to track our cycles and avoid or get pregnant.
But the Church also understands that there is such thing as too many children or not being finanically or emotionally ready for them. They want happy, healthy families just like any other institution. Which is Natural Family Planning (NFP) or Fertility Awarenss Method (FAM) is endorsed and encouraged by the Catholic Church as a natural way to avoid pregnancy without taking God out of the mix. This method is not the rhythym method. The rhythym method relied on the theory that every woman has a 28-day cycle and was fertile during the exact middle of that cycle. We know now that that is not true. NFP/FAM relies on science and observation to carefully track each woman's cycle and help her to know when she is fertile, because a woman is actually only fertile 3-4 days a cycle.
I may seem like a terrible poster child for NFP/FAM, but I can tell you that this method has a higher success rate than any hormonal birth control or barrier method. I can also tell you that like any medication, hormonal birth control can and does have serious side effects. Hormonal birth control effects not just your menstrual cycle, but 150 different functions of the human body. It also effects every single one of our organs. It even effects our eyes. And these side effects are brushed aside. Taking hormonal birth control is not a decision that should be made lightly. The barrier method has less negative impacts. But it does interefere with the natural course of having a child. Each time a couple has sex without a barrier method, the woman's body learns to recognize that man's particular sperm, which leads to an easier pregnancy because the possibly resutling baby isn't a foreign object. There is also evidence that this can be healthy for women because it passes on antibodies that the man has devleoped that she may not have. Crazy!
Simply, the Church believes in the sovereignty of God and respecting what our bodies were made to do. Fertility is not a burden, it is a blessing. We should not have to pump our bodies full of chemicals to prevent them from doing what we were made to do. If you are really interested in NFP/FAM, I would highly reccomend taking some time to browse through this YouTube channel, Femme Head, https://www.youtube.com/channel/UCRxM7IbVgPEOPvi_2qBd3mw and watching some of her videos. She is not Catholic, which I think actually enhances what she has to say about hormonal birth control and why NFP/FAM is a viable option for our fertility. You can also go visit USCCB's site on NFP/FAM to better understand what the Church's official opinion is http://www.usccb.org/issues-and-action/marriage-and-family/natural-family-planning//
Now, I am not a doctor or any medical professional. But I can tell you that there is something to be said about fertility awarenss rather than trying to cancel yourself out. I can also tell you that my particular experience with NFP/FAM was half-hearted because I was under the impression that could not get pregnant, so don't use me as a reason to try it. Just look at my parents, they decided to have after seven years of NFP/FAM.