October 4, 2019
Fewer U.S. mothers are “seeing double” on delivery day, according to a new report from the U.S. Centers for Disease Control and Prevention.
Having twins heightens health risks for both the babies and the expectant mother, so specialists see the decline as good news. Researchers believe that the decline may reflect advances—such as the use of artificial intelligence— in reproductive technologies, including in vitro fertilization, that result in fewer multiple births.
“I am elated,” Dr. Amanda Horton told the Journal. She is a maternal fetal medicine specialist for the online Maven Clinic who lives in Austin, Texas. “What I take away from this is that we’re working hard to ensure that families have the healthiest pregnancies possible.”
In the report from the CDC’s National Center for Health Statistics, published on October 3, the rate of twin births dropped to 32.6 from 33.9 for every 1,000 births, a difference of 11,800 fewer twin births in 2018 compared with 2014.
The drop occurred among white mothers aged 30-54, the Journal reports. The rate for black and Hispanic mothers and mothers under the age of 30 essentially remained unchanged.
Twin births in the U.S. started exploding in the 1980s, with an increase of 79% from 1980 to 2014.A change in maternal age may have influenced the increase, experts say, as women started having children later in life. Older mothers are more likely to have twins because they are more likely to release multiple eggs during one menstrual cycle, Dr. Horton said in an interview with the news outlet..
The early 1980s also saw the rise of assisted reproductive technology, especially in-vitro fertilization, after the first IVF baby was born in the U.K. in 1978. Between 1981 and 2015, more than one million babies were born in the United States with the help of reproductive technologies, according to a 2017 report from the CDC and the Society of Assisted Reproductive Technology (SART).
With IVF technology, especially in the earlier years, families and physicians opted to transfer multiple embryos into a mother’s womb to increase the chance of pregnancy. That is no longer the case. Improved techniques for embryo freezing and genetic testing have bettered outcomes when transferring a single embryo.
CDC data show that the percentage of embryo-transfer procedures that transferred only a single embryo roughly doubled from 2013 to 2016 in all age brackets above 35 years old, and professional groups now recommend the practice in most cases.
Despite the decline, the rate of twin births today is still nearly double the rate in 1980.
Research contact: @WSJ