This has come up from time to time, on a whole variety of blogs (typically as a throw-away line about those wacky triplet folks, so undeserving of their media fame and so unethical with the inappropriate ART protocols--yes, I know I've gone there, too), so let's just get it out of the way: Not every triplet pregnancy resulted from infertility treatment. In fact, something like 1 in 10 triplet pregnancies is a surprise: no fertility treatments were involved. Needless to say, those pregnancies are a special kind of shock for the expectant parents. Imagine finding that out at 20 weeks. Hang out with enough mothers of triplets and you'll find out: it happens. Oof.
Here are some of the numbers: According to various sources, there's one spontaneous triplet pregnancy for every 6,000 to 8,000 pregnancies in this country. John Elliott proposes a ratio of 1 in 6,900 and from that, estimates that there are about 580 spontaneous triplet pregnancies a year. Mothers of SuperTwins reports that fourteen percent of their membership conceived without fertility treatments. Pediatrics published an article claiming that between 1997 and 2000, 17.7% of high-order multiples were conceived spontaneously. The CDC reported that there were 6,737 high-order multiple births in 1997. Even if none of those births were of quads+, John Elliott's estimate of 580 spontaneous triplet pregnancies would be 8% of the total.
How do you conceive spontaneous high-order multiples? Most of the time, you ovulate twice (the same profile as spontaneous fraternal twins), and then one of the embryos divides. A set of identical "twins" plus a fraternal baby is the classic makeup for spontaneous triplets. Far less often, a single embryo divides, and then one of the twins divides again: voila, identical triplets. Also rare, but not unheard of, is the set of three fraternal spontaneous triplets. It's not at all common for a woman to produce three ova in one cycle (most ovaries not high on drugs want to mature only one follicle at a time), but it happens.
When does spontaneous high-order birth happen? Hard to generalize, but it tends to follow the same patterns as spontaneous twinning: in the teenage years, when fertility is at its peak, as well as toward the end of one's reproductive life, when hormonal fluctuations (for the fertile, obviously) can also contribute to multiple ovulation. Spontaneous twinning, of twins or more, also seems to happen to the fertile in the early months of a relationship: the more sex you're having, the more likely you are to conceive during that oddball month when you've happened to ovulate twice.
So really, folks, enough already with the comments about how triplet parents deserve whatever they've got coming. Even if I'm willing to concede the point when it comes to those of us who used drugs (as so many strangers like to phrase it in the aisles of Target or on the streets where we live)--and hey, I think I've written enough conflicted posts about that subject--about ten percent of us didn't do anything more offensive than have sex. Granted, these folks redefine Fertile Myrtle, and that can be pretty offensive, or maybe a better phrase is bitter-making, if you're struggling just to conceive one, but the point is, no, not every triplet you see is an IVF baby. Besides which, every parent of triplets, at some point, loses patience with the way the mere existence of our kids somehow becomes a status-marker for the health and functioning of our sex organs. Please, can we make jokes about the triplets that focus on something else now? Did I mention that when you line them up together in a crib, they try to nurse each other's heads? That's pretty darn amusing, I think.