What Are The Chances of Having Twins?

Two For One

Twin pregnancies are uncommon, but IVF or other fertility treatments can increase the chance of having multiples. Twin pregnancies need careful monitoring.

Most people who picture a bouncing bundle of joy picture one bouncing bundle of joy. A majority of pregnancies are singletons, although the rate of twins has increased somewhat due to the prevalence of IVF and other fertility treatments. In 2013, twins accounted for about three out of every 100 births in the United States. Having in vitro fertilization increases your chances of having twins. Depending on the age of the mother, between 15 and 30 percent of IVF procedures result in twin pregnancies.

Identical or Fraternal Twins

Sets of twins can be either identical or fraternal. Fraternal twins happen when two separate sperm fertilize two separate eggs at the same time. Fraternal twins are not necessarily the same gender, may not look similar to each other and are no more alike than full siblings born during two different pregnancies. Identical twins happen when a single sperm fertilizes a single egg. For unknown reasons, that single embryo splits into two and continues to develop into two separate babies. They are always the same gender, look very similar and are genetically identical. Identical twins are much less common than fraternal. The rate of identical twins has remained relatively consistent at about one in 285 pregnancies.

Spontaneous Twin Pregnancies

About three percent of pregnancies result in twins, with fraternal twins being much more common than identical. There's no sure way to guarantee twins, but some factors make it more likely for a woman to conceive multiples. One significant factor is the family history of the mother. If your extended family photos are full of fraternal twins, it's more likely that you'll conceive twins. A family history of identical twins does not increase your chances of twins in the same way. Age is also a factor. If you are over 30 years of age, you're more likely to conceive twins due to an increase in follicle-stimulating hormone that makes your body more likely to release multiple eggs during ovulation.

Fertility Treatment and Twins

Undergoing certain types of fertility treatment can increase the chances that you'll conceive twins. In vitro fertilization, or IVF, is a procedure involving implantation of fertilized embryos into your uterus. Because more than one embryo is often implanted, it is more likely that multiple embryos will "stick" and grow into babies. Due to the risk of higher-order multiples, many fertility clinics have policies about how many embryos they will implant during each attempt. Medications that stimulate egg production also increase the risk of fraternal twins, since they can cause you to release more than one egg during ovulation. Depending on the type of treatment and the age of the mother, between 15 and 30 percent of successful fertility treatments results in a twin pregnancy.

Special Considerations

Although having twins might sound like fun, a twin pregnancy does carry an increased risk of complications. Twins are more likely to be born before 37 weeks of pregnancy, which can mean a stay in the neonatal intensive care unit, or NICU, after birth. Preeclampsia, or very high blood pressure during pregnancy, is also more common in women carrying twins. Because of these and other increased risks, a twin pregnancy is typically monitored carefully to make sure that you and your babies stay healthy. Twin pregnancies are typically discovered during a first trimester ultrasound, which gives both you and the doctors plenty of time to plan and prepare.

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