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First, the incidence rate of having twins or supertwins (as triplets and more are referred to now) in general:
| Type of Birth | Ratio of live births |
|---|---|
| (courtesy of the National Organization of Mothers of Twins Clubs, Inc.) | |
| Twins | 100,750 (about 50,375 sets of twins) |
| Triplets | 5,298 |
| Quadruplets | 560 |
| Quintuplets or higher order | 81 |
And yes, says NOMOTC, the twinning rate is on the rise, primarily due to an increase in older women having children and to fertility drugs. To view more statistics on the incidence of multiples throughout the world, see "Facts About Multiples". Many use this rising incidence to declare the need for mandatory restrictions by the U.S. government on reproductive technologists, similar to those placed on practitioners in other countries. At present, the American Society for Reproductive Medicine has issued its revised "Guidelines on Number of Embryos Transferred" (a PDF file) for members of that society and hopefully others involved in fertility treatment.
According to the website of Parents of Multiple Births Association of Canada, it is estimated that ''Overall 15-17% of multiple births result from infertility treatments, however, it is estimated that 60% of triplets, 90% of quadruplets and 99% of quintuplets result from these treatments."
The incidence of multiples varies with the drugs and procedures used by patients, in addition to variables such as maternal reproductive health. Clomiphene citrate has a relatively low multiples rate, around three to six percent, usually twins. Injectable menotropins (such as Metrodin, Pergonal, Humegon, and Repronex) and gonadotropins (like Gonal F and Follistim) have demonstrated an overall multiple rate (based on live births) of 15% to 20%, and a triplet or more rate of 5% to 25% percent. In general, patients undergoing IVF are 10 times more likely to experience a multiple birth than women in general; it should be noted, however, that the famous McCaughey septuplets and Chukwu octuplets were all conceived without invitro fertilization.
© Tracy Morris
