Over the past 40 years, the number of multiple births in the United States has doubled. According to experts, this is due to the extensive use of assisted reproductive technologies in the treatment of infertility.
The results of a study conducted by a team of authors from the Brown University show that the number of multiple births in the United States from 1971 to 2011 has increased from 1.8% to 3.5% (of the total number of births).
Researchers estimate that 75% of the births of triplets and more than 30% of the births of twins in 2001 were caused by medical intervention.
At the same time, the number of triplets conceived with the help of in vitro fertilization, has decreased over the last three years from 48% to 32%. But the number of multiple births that occurred as a result of the use of other methods of infertility treatment has increased from 36% to 45%.
The study authors think that this phenomenon is determined by the fact that during the IVF procedure the number of transferred embryos can be controlled, while upon stimulation of the ovaries it is difficult to predict how many eggs will be fertilized eventually.
The results of the study are commented by one of its authors Eli Adashi, the professor of obstetrics and gynecology: "Some couples rely on twins as a result of treatment, but more often multiple pregnancy is not desired. In these cases parents and children are exposed to unpredictable medical risks and financial expenses for a long time, which the physicians should seek to prevent".