Seeing Double – and Triple – After IVF

Fertility treatments and IVF contributed to increase in twins and other multiple births

/ Author:  / Reviewed by: Joseph V. Madia, MD Beth Bolt, RPh

(RxWiki News) The development of fertility treatments and in vitro fertilization (IVF) has offered tremendous new opportunities for individuals to become parents. But they came with unintended consequences too.

A recent study determined how much fertility treatments and IVF have contributed to the increase in twins, triplets and other multiple births.

IVF is a process in which an egg is fertilized by sperm outside of the body, and then the embryo is implanted in a woman's body.

The world's first IVF baby was born in 1978, and non-IVF fertility treatments have been available since the late 1960s.

"Discuss fertility treatment options with your doctor."

This study, led by Aniket D. Kulkarni, MPH, of Women’s Health and Fertility Branch of the US Centers for Disease Control and Prevention (CDC), looked at the extent to which fertility treatments were contributing to multiple births.

Multiple births are when mothers have twins, triplets, quadruplets or a another multiple number of children in one pregnancy.

The researchers estimated the rates of multiple births for three different time periods:

  • 1962-1966, before fertility treatments were available
  • 1971-2011, national birth rates data
  • 1997-2011, data from in vitro fertilization records

The researchers used these three sets of data to estimate how many multiple births were due to IVF or non-IVF fertility treatments after taking into account mothers' ages.

Then the researchers specifically examined multiple births from 1998 onward. It was in 1998 that clinical practice guidelines were introduced with the goal of reducing multiple births.

The researchers determined that just over a third of all twin births (36 percent) by the year 2011 had resulted from fertility treatments.

From 1971 to 2009, the researchers calculated that twin births essentially doubled.

Meanwhile, 77 percent of all triplets and higher numbers of multiple births by 2011 had resulted from fertility treatments, the researchers estimated.

These multiple births increased by a much greater factor than twin births since fertility treatments became available.

From 1971 to 1998, the rates of triplets and higher-order multiple births increased by 6.7 times.

However, after 1998, the rate of these higher-multiple births began declining, and they decreased 29 percent from 1998 to 2011.

This decrease occurred alongside a 33 percent decrease in triplets and higher-order multiple births specifically among IVF-conceived children.

At the same time as the decline in triplets and higher-order multiple births, there was a 70 percent drop in the practice of transferring three or more embryos during IVF.

The researchers concluded that multiple births had increased as a result of fertility treatments during the past 40 years, but these rates have been decreasing with the new guidelines of transferring fewer than three embryos at a time during IVF procedures.

This study was published December 5 in the New England Journal of Medicine.

The research was funded by the CDC. One author has received fees for serving on the membership board of Alere, in which he also holds stock. No other potential conflicts of interest were reported.

Review Date: 
December 6, 2013
Last Updated:
December 6, 2013