|What the New York Times article doesn't mention is that yes, fertility clinics are implanting fewer embryos, but they are also still using selective abortion to whittle down the number of kids being born. A woman might have four embryos implanted (a not unusual number), in the hope that one becomes viable. If three become viable, she might elect to have one or two selectively aborted. Voila, fewer triplets being born.
"Older mothers are more likely to have a multiple birth, and the increase before 1998 was largely attributed to rising average maternal age, according to the lead author, Joyce A. Martin, a statistician with the N.C.H.S.
“Age of mothers has continued to increase,” she said, “so you would expect the rate of triplets to increase. So the decline cannot be attributed to any changes in maternal age.”
“We think the decline is likely largely related to changes in fertility therapies, particularly assisted reproductive technology,” she added.
Fertility centers now are urged, for example, not to implant multiple embryos in women receiving treatment."