ART and Multiple Births

Key Findings: Fertility Treatments and Multiple Births

Multiple births—the delivery of twins, triplets, or more—is common with fertility treatments. During the use of assisted reproductive technology (ART)—such as in vitro fertilization (IVF)—multiple births primarily result from transfer of more than one embryo during the procedure. Non-ART fertility treatments include oral medications or injections used to boost ovulation among women who do not ovulate or to stimulate the development of multiple eggs among women who have trouble getting pregnant. Because it is difficult to predict or control the number of eggs that will be fertilized during non-ART fertility treatments, many of these treatments also result in multiple births. Although some infertility patients may prefer to have twins, all multiple births, including twin births, have higher risks for both mother and infants.

The following key findings can be used by patients, providers, researchers, and public health specialists to better understand how fertility treatments contribute to multiple births and ways to improve the chance of healthy infant birth when using fertility treatments.

Are multiple births increasing or decreasing in the United States? How do fertility treatments contribute to this trend?¹

• Over the last 4 decades, twin births nearly doubled. Triplet and higher-order births quadrupled. This increasing trend coincided with the introduction of fertility treatments such as ovulation induction, ovarian stimulation, and in vitro fertilization. 
• After taking maternal age into account, more than one-third of twins and more than three-quarters of triplets and higher order multiples in the United States resulted from conception assisted by fertility treatments.
• ART practices are improving. Over the past decade, fewer embryos have been transferred during ART, resulting in fewer multiple births from ART.
• Non-ART fertility treatments of ovulation induction and ovarian stimulation contribute to a portion of the increasing number of multiple births. However, the outcomes of these treatments are not routinely tracked in the United States. To better understand trends in births from non-ART fertility treatments, these data are needed.

How many embryos should be transferred during an ART cycle to achieve the best outcome^2,3?

• Our findings can inform the development of future guidelines on the number of embryos transferred during ART by providing a measure of success that emphasizes good perinatal outcome.
• The best outcome of ART is the birth of one healthy infant. Among younger patients undergoing their first ART cycle, the best outcome can be achieved when a single embryo is selected for transfer.

More About These Findings

These studies used CDC’s National ART Surveillance System, which collects data on all ART procedures performed in the United States.

More Information about ART and Multiple Births

• Learn more about assisted reproductive technology and CDC’s work on this issue.
• Visit NCHS’ website to learn about the number of multiple births in the United States.

Key Findings References

1. Kulkarni AD, Jamieson DJ, Jones HW Jr, Kissin DM, Gallo MF, Macaluso M, Adashi EY. Fertility treatments and multiple births in the United States. N Engl J Med. 2013 Dec 5;369(23):2218-25.
2. Kissin DM, Kulkarni AD, Kushnir VA, and Jamieson DJ for the National ART Surveillance System Group. Number of Embryos Transferred After In Vitro Fertilization and Good Perinatal Outcome. Obstet Gynecol. 2014 Feb;123(2 Pt 1):239-47.
3. Kissin DM, Kulkarni AD, Mneimneh A, Warner L, Boulet SL, Crawford S, Jamieson DJ; National ART Surveillance System (NASS) group. Embryo transfer practices and multiple births resulting from assisted reproductive technology: an opportunity for prevention. Fertil Steril. 2015 Apr;103(4):954-61.