Multiple births, when a woman is carrying twins or more in a single pregnancy, have risen significantly in the last 30 years. While the average woman has just a 3 percent chance of giving birth to twins, there has been a 60 percent increase in twins since 1980, according to the National Center for Health Statistics.

One of the major reasons for this change is that women are delaying childbirth, and twins become more common as women age.

Because fertility also declines with age, many women, especially those who have reached “advanced maternal age,” are pursuing infertility treatment. One of the most common fertility drugs used to increase a woman’s chance of ovulating is clomiphene citrate, commonly known as Clomid. Women using Clomid have a one-in-five to one-in-10 chance of conceiving twins.

Medications like this, as well as technological advancements such as intra-uterine insemination and in-vitro fertilization, definitely increase the chances for twins and higher-order multiple pregnancies, such as triplets, quadruplets and even octuplets. It is estimated 60 percent of triplets result from fertility-enhancing treatments, and these treatments are also responsible for 90 percent of quadruplet pregnancies and 99 percent of higher-order multiple pregnancies.

Though women who conceive one set of fraternal twins without fertility enhancement have a four-fold increase of having twins again in a later pregnancy, the possibility of having spontaneous triplets without any infertility treatment is one in 8,100. Given these odds, it is clear that the substantial rise in multiple births is more likely a result of women delaying childbearing and advancements in available infertility treatments.


Dr. Michael Urig is chief of obstetrics and gynecology at Banner Good Samaritan Medical Center. For more information, talk with your doctor, or call Dr. Urig’s Ahwatukee Foothills office at (480) 759-9191.

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