Because most philosophies that frown on reproduction don't survive.

Wednesday, January 28, 2015

Does NFP work? Do you see my 11 kids?

Someone on Facebook posed the question: "Why do all NFP teachers seem to have 5 kids?" It's a good question: if NFP works, why are these people always pregnant? One answer is that they want to have lots of children, which is a good thing but does raise the question of whether they practice the system they preach. But probably a more accurate answer is: do you know how many more kids we'd have without NFP?

So I did a little math on the subject I know best: myself. I have been married for 14 years minus 5 months, so 163 months. I had my first baby 15 months after I was married. My fertility returns, on average, 6 months postpartum (second child, 15 months younger than the first; and careful observation after the other four births bears that out). So, a fifteen month cycle between possible pregnancies. Had I not used NFP and gotten pregnant on a fifteen-month schedule, well, 15x11= 165. After being married for 162 months, I could be six months pregnant with my 11th child.

Let me restate that. I could have 11 children by my 14th anniversary without NFP. I will have six, almost half that number.

Now this isn't carved in stone. One won't necessarily get pregnant in a given cycle; I myself have gone several cycles without conceiving even when I was trying to. (Observation says that results in boys, BTW.) But you can't know that except in hindsight, and I do know that I can get pregnant even when I'm trying not to conceive; it's happened three times. (Observation: A girl, a miscarriage, and a girl.)

After the surprise of my second pregnancy, all my children have been spaced with NFP. The second closest spacing is 22 months -- still closer than I'd intended, but far saner and healthier than a 15-month spacing. As I get older and my pregnancies get tricksier, that spacing -- and the physical condition it allows me to recover -- become more vital. I was only 23 once.

So, I'm not an NFP instructor, but people may see my six kids and wonder, "Does NFP work?" And the answer is, "Do you see my 11 kids? No? Then I can assure you that it does."


Anonymous said...

Keep in mind that the NFP materials often promise something close to 98% effectiveness. That has...not been our experience (or, it appears, yours). ; - ) Does it work? Yes. Is it as effective as promised? No.


Jenny said...


Actually if you do the math, it does bear that out. 73 months of potential fertility and getting pregnant twice mean NFP worked 97% of the time.

Jenny said...

That would be getting pregnant unexpectedly twice.

Jenny said...

Anyway I am not nearly the poster child of this argument because 1) we didn't use NFP before my oldest and 2) I have four children and if I had conceived as quickly as possible since we started using NFP, I would probably only have five and that fifth would still be a newborn.

The scary part of NFP is not that it doesn't work, but that it softens your heart to want more. *That's* why the NFP instructor always has five kids.

Darwin said...

I believe that the percent accuracy is supposed to be over the course of a year. In other words, if you use NFP to avoid pregnancy and do it correctly, you're supposed to have a 97% chance of not getting pregnant during that year.

However, I don't think those numbers are very reflective of the real world. One of the reasons is that using NFP just a little bit badly (being off by a couple days) can mean nailing the exactly days when you're most likely to get pregnant. So unless you build in a lot of room for error, most mistakes are big mistakes.

Whatever the reason, I don't think the perfect usage numbers reflect very well how most couples will experience real world usage results.

MrsDarwin said...

I don't support holding people up with false hopes, either for NFP or ABC, though I do think it's hard to get good numbers for either because fertility varies from woman to woman. Did Mrs. A not get pregnant this month because she's on the pill or because she simply had subpar fertility or the sperm didn't reach the egg or whatever?

So the equal and opposite question is: Are hormonal contraception, prophylactics, or other means of artificial birth control as effective as promised either? Here's an anecdote (not data, of course, but not irrelevant): all the women Darwin knew at his previous Big Tech employer who got pregnant were using birth control when they conceived. Surprise pregnancies happen.

Here's some more of my numbers. I'm on my 79th chart, and we'll call it 80 to account for the cycle I didn't conceive between wedding night and conception. Three of those cycles resulted in unintended pregnancies. 3 unintended pregnancies /80 observed cycles = 96.25% effectiveness. Not 98%, but not far off. Everyone else's numbers will vary, of course, because my fertility comes back early and that gives me a lot of cycles, some of which are a good deal longer than 30 days.

Also: my surprise children are the delight of my life, so there's that.

Jenny said...

Oh, over the whole year. Well that does mean it is less effective, but I'm not sure exactly what the denominator should be. If you only count potential months and divide by years, that would be 67% effective. But I'm no statistician.

Still though, I maintain the real danger is that it opens your heart to more children than you otherwise would have thought you wanted.

MrsDarwin said...

Actually, 81 cycles, to account for the unobserved cycle that resulted in #2. Breastfeeding is also not always an effect method of spacing.

bearing said...

I have been married sixteen years, have had five children (no miscarriages), and every one was planned. In other words, I am batting 100%, so far.

I guess we're just the planning type, and we know what kind of spacing supports well-being for us: about 3 years.

My fertility returns about 9 months postpartum, and we've always conceived in the first two cycles of trying. So without it we'd have, let's see, about the same as the Darwins, i.e., 11.

That's assuming that we didn't, out of fear of more pregnancies and ignorance of the fertility timing, just start unconsciously avoiding each other and letting our desire and affection deteriorate to the point where we only touched each other one or two times a month or less often.

Jenny said...

I have one "NFP Failure" child. I was still learning (well I am *still* learning) and made a colossal mistake which is laughable in hindsight. I am not going to say that I love this child more than my other children because I don't, but I will say that I think I am more grateful for her or I feel gratefulness in a different way towards her. She was a pure gift. I did nothing to plan her. I did not merit her in any way, but I was still given this cup that was packed down and overflowing.

Darwin said...

I believe the way the studies are supposed to work is: They take a large group of women using some given type of birth control, monitor them for a year, and see how many get pregnant. The percent effectiveness represents the percent who were not pregnant at the end of a year.

Josiah Neeley said...

The New York Times has a handy chart that shows the in practice effectiveness for various methods (NFP is called "Fertility Awareness").

Basically NFP works about as well in practice as spermicides and sponges. Condoms and diaphragms works a bit better and the pill works a bit better than that. Over a ten year period, though, the only methods that don't include a substantial chance of an intended pregnancy are IUDs and sterilization.

Jenny said...

I have calculated how many children I think I would have been capable of producing if I had started with NFP and projected it out to what I foresee as the end of fertility in the future. I think that number is probably nine. Two of those probably would have come before my oldest so any fewer than seven children by the time I am finished will by my NFP differential.

Darwin said...

I would definitely agree with Jenny's point, too, that NFP has a tendency to create openness to more children.

Darwin said...


For a relative comparison, it's probably decent, though Leah Libresco had some good objections to the way they pushed their numbers out over time:

BettyDuffy said...

I have no surprise pregnancies, though none were planned.

I think one reason NFP couples have more children is that they don't have to make a decision, go off the pill and "try" to conceive.

Sometimes you just want to "do it" more than you don't want to get pregnant.

Lauren said...

As I'm currently pregnant with a little NFP mistake, I'm not too happy happy about the method. I've never felt comfortable with it. I don't have one of those easy to read bodies. I've observed fertile mucus maybe three times ever. I'm really at a loss for what we do after this child is born. I may have to find a NFP teacher who offers weekly or daily lessons. I can't be the only one who also feels resentful that this is all my (the woman's) job. It's a lot of consistent methodic behavior and data collection that only I can do. This is not my area of greatest strength. Ironically my husband would be great at it, but that's not really an option. I think we have a whole lot of abstinence in our future. I'm under no illusions that life on birth control would make everything ok. I have a cousin who got pregnant with an IUD. But NFP is not an easy alternative by any means, at least for me. At the moment this pregnancy is really only highly inconvenient, as our youngest child has special needs. I was hoping to get her settled into preschool before conceiving again. If I had a serious medical problem and couldn't get pregnant, I think we'd have to completely abstain. I suppose that's sort of the point of NFP to keep you always thinking about your actions and their natural consequences. Right now it's a cross.

bearing said...

Lauren, it's definitely a cross. I would say it's a cross for all of us, though some more than others, and it's a highly individualized cross.

The 100% doesn't come "easy" for us. We historically have been quite conservative in our decision-making, which is "difficult" in a different sense that it can be for others "difficult" to figure out a complicated and ambiguous chart.

I would sum it up as "It has worked well for us, and for us that's because we've chosen a harder path than we might have."

Anonymous said...

Lauren, as a man whose wife likes to leave in a few days margin of safety*, I've gotten used to the monthly abstinence and even come to see it as an opportunity for growth, & self-discipline. It's also an opportunity to dialogue, watch a show, or do something else together. I resented it at first, and I think my wife resented being the gatekeeper, as it were, but ultimately its helped me be more thoughtful and gentle, and helped us grow together.

*My wife gave up completely on daily observations after a few years, and just tracks periods with an iPhone app; therefore she likes a few days extra margin, and so far no surprises.

JoAnna Wahlund said...

I've been married 13 years, and have had seven pregnancies (5 kids, two miscarriages). Only one of those pregnancies was unplanned. (We also contracepted for the first two years of our marriage, before our conversion to Catholicism.)

JoAnna Wahlund said...

Also, re my "unplanned" pregnancy above, I was charting rather sloppily so it was definitely preventable user failure.

JoAnna Wahlund said...

Lauren, check out the Marquette method. It uses the Clearblue fertility monitor so no mucous interpretation required. It has a great postpartum/breastfeeding protocol too.

Anonymous said...

For some of us NFP simply doesn't work to prevent pregnancy, yes it may add a few more months in between pregnancies but it doesn't prevent them. I have known women who have gotten pregnant at times when it was scientifically impossible (by NFP standards) only to take their chart to their fcp and be told that they must have charted wrong- because the chart is perfect and you shouldn't be able to get pregnant this way. It is not a very supportive system that says "use our method it is almost 100% effective" and when it isn't very effective for some instead of getting understanding getting shamed into "you are either an idiot or made some error or have no willpower and THAT is why it didn't work to prevent a pregnancy". I did not enjoy my first 4 children because I always looked at them knowing another one was around the corner before I was ready. After a few more children who I wanted to adore and love without worry my husband and I agreed to what many other Catholic couples do- complete abstinence. It is a cross, a hardship on my marriage and has made me question whether or not I can remain a Catholic.

Anonymous said...

"I believe that the percent accuracy is supposed to be over the course of a year. In other words, if you use NFP to avoid pregnancy and do it correctly, you're supposed to have a 97% chance of not getting pregnant during that year."

Yeah, and that's where the 73 months Jenny refers to kind of proves the point. Based on the post (with apologies to the Darwin's for any rudeness), this suggests a "failure" rate of three in six years (72 months). Don't get me wrong, we have a biologically impossible (according to the chart) three year old who is a great joy in our lives; there are many, many worse "mistakes" to make in life. But I think over-promising the effectiveness of NFP is not helpful, particularly when it results in folks insisting that "no, you just messed it up," whenever someone questions whether NFP is as effective as advertised.


Anonymous said...

I don't mean this critically as it sounds like you are happy with how NFP has worked for your family- but I'm not sure I follow your logic on how 3 unplanned pregnancies in 14 years is a good testimony to NFP's effectiveness. All of the modern methods claim to be 99% effective per year with correct use- so while your personal track record is better than doing nothing, it's far, far below what all NFP organizations claim. If not too personal, could you comment on whether your surprise blessings occurred when you were consciously breaking rules or slacking on charting, or whether they were method failures?

I'm a Catholic NFPer so I'm on your "team" so to speak. I've been fortunate to have cycles that are easy to navigate with NFP and have never had an unplanned pregnancy.

But I know this is a huge struggle for many couples. I guess it just feels like the Catholic blogosphere talks out of both sides of its mouth on this one. During NFP Awareness Week, we're trying to convince the world that NFP is easy, simple, and more effective than the pill. Then on a personal level, lots of people explain that they find it almost impossible to use, or admit that they've had multiple surprise pregnancies. I think NFP is awesome and I want everyone to use it- but I'm concerned that this kind of thing hurts our credibility.

MrsDarwin said...

Lauren, that sounds very frustrating.

We never consciously break rules or "cheat". Biology doesn't care if you didn't mean it or if it just kinda happened, and we don't play around with that. If it seems like a fertile time, and we've asked ourselves, "Are we okay with getting pregnant this month?", and if the answer is no, we don't have sex that night. This has led to months of abstinence during the return of fertility when the signs are ambiguous, and long stretches when the cycles are regulating out postpartum. It is what it is. I only slack on charting when I want to conceive, or after clear phase III.

My first surprise was not a method failure per se, since we weren't charting then. I bought the line that breastfeeding was a surefire means of infertility up to a year postpartum, and it didn't ever occur to me that I'd get pregnant 6.5 months after having a baby. I didn't have a period between pregnancies, which lead to some amusing exchanges at the doctor's office, ha ha.

My second surprise was my miscarriage. It's an old chart and I'm not going to dig it up to prove a point, but it was more than four days after temperature rise, and drying signs to match. I've always wondered if the pregnancy wasn't viable because conception was on such an extreme edge of fertility, and something was wrong there.

I'm looking at my chart for my third surprise. Five days after peak, not perfectly dry but definitely progressing, two days of 7/10 temp rise with a day between them of much lesser rise, but still above low temp level. It was not a call we felt at all conflicted about making. This was even the second peak of the cycle, with no temp rise after the first. We were absolutely flabbergasted, and not in a cute way, to be pregnant; you can read about it here.

I don't find NFP impossible to use, actually. After about a year postpartum, my cycle evens out and becomes more predictable. The hardest part is the the accountability each month, determining whether or not this is a month, or a night, to abstain. RIght now the meta-reason is very clear: my baby is only 13 months old, and due to progressively more tricky pregnancies, I need to be healthier and in better shape before I think about getting pregnant again. Holding fast to that on particular nights, especially if it means adding a day or so of extra waiting into the equation, is where theory has to meet practice.

As for my effectiveness testimony: well, again, I don't have eleven children right now (or ten and counting) so each extra month of spacing is further proof of effectiveness, to me at least. Effective =/= awesome. I'm not a cheerleader for NFP, nor is it my lifestyle. I just think it's better than the other options, and I'd rather be frustrated than be in mortal sin, so there's that.

Unknown said...

I'm glad Grandma Day had at least 8 by her 14th anniversary =)

bearing said...

Anonymous said,

"my husband and I agreed to what many other Catholic couples do- complete abstinence."

Do you really think that MANY Catholic couples go to complete abstinence these days?

Because that seems unlikely to me. It's just a feeling, granted, but I was wondering if you had some data that I don't.

Anonymous said...

I think also some people don't understand the biology behind conception and so assume that a few days before they are to be fertile that they are in the "safe zone" - sperm can survive between 60-80 hours in the uterus and since fertilization occurs in the fallopian tubes, it is completely possible that if you have sex 2-3 days before ovulation that you're setting yourself up for conception.

bearing said...

More than 2-3 days before ovulation is possible. The window is something like from 5 days prior to ovulation to 48 hours after.