The number of multiple births from assisted reproductive technology continues to decline, with no more than 1% of women undergoing the procedures delivering triplets or higher orders of multiples in 2011.
In fact, in the highest-risk group of women aged 42 years and older, there were no higher-order multiple births at all that year, according to David Ball, Ph.D., president of the Society for Assisted Reproductive Technologies (SART).
G. David Ball, Ph.D
"We are working toward an extinction of these pregnancies," especially in older mothers, Dr Ball said in an interview. "This report shows that we’re making progress."
The group has released its latest data, providing a picture of assisted reproductive technology (ART) results in 2011. Among 379 clinics, there were 154,412 ART cycles, resulting in the birth of 59,446 babies.
The continued decline in higher-order multiple births is a key finding, and one that confirms clinical improvements in a number of areas, Dr Ball said in an interview.
"Physicians who create the fertility treatment plans are getting much more sophisticated in being able to identify which plans will give the best egg quality in each individual patient. As a result, we’re starting out with good-quality eggs, which lead to good-quality embryos in the lab. There have also been improvements in the culture techniques, so we’re growing healthier embryos. And the final piece is that we’re getting better able to identify which embryo in the lab is the most likely to implant," said Dr. Ball.
And because clinics are growing better embryos, many women are choosing elective single-embryo transfer – another factor in keeping the multiple rates down.
In 2004, the first year SART recorded these numbers, 1% or fewer of women in each age group elected to have just a single embryo transferred; up to 6% of pregnancies were triplet or more.
By 2010, the single embryo transfer rate had risen to about 10% in women younger than 35 years. In 2011, the percentage of single embryo transfers was close to 12% for women aged 35 years or younger; 11%-31% of pregnancies were twins, and less than 1% were higher-order multiples.
"Single embryo transfer is being more accepted by professionals as well as patients," Dr Ball said. "But the decision always has to be balanced between maximizing the change of pregnancy and minimizing the chance of a multiple birth."
Frozen transfer rates from nondonor oocytes are also up from the 24,743 performed in 2010 – another good sign. In 2011, there were 28,166 frozen embryo transfers. The rates of live birth were similar to those in 2010, ranging from 39% for women younger than 35 years to 24% for those aged 41-42 years, and 16% for those older than 42 years.
"Hopefully, this means women and their physicians are confident they can get another good chance with frozen embryos, and this helps them become more comfortable with the idea of a single embryo transfer," Dr. Ball said.
Overall, women younger than 35 years continued to have the best results, the report indicated, including:
• 40% of cycles resulting in live births.
• 46% of transfers resulting in live births.
• 36% implantation rate.
• 31% of live births with twins.
Pregnancy results were inversely related to age. For those aged 41-42 years:
• 12% of cycles resulted in live births.
• 17% of transfers resulted in live birth.
• 9% implantation rate.
• 15% of live births with twins.
SART has also created an online registry that allows easy access to all of the outcomes data from 2004 to 2011.
It also allows patients and physicians to examine outcomes in each SART member fertility center. A "hover" feature facilitates patient understanding by providing explanations of technical terminology. Patients can search for a facility by distance by entering their zip code as well.
No disclosures were given.