Where have all the triplets gone? The mystery explained: ScienceAlert

The rise and fall of triplet births in the US is a dangerous roller coaster that thankfully appears to be stabilizing.

In the 1980s, the number of triplets born in the country suddenly exploded, increasing fivefold in just two decades.

From that peak, however, the number of multiple births from a single pregnancy has taken a dramatic plunge.

According to a new report from the Centers for Disease Control and Prevention (CDC), the number of births of triplets and higher order dropped by almost 65 percent between 1998 and 2023.

At the same time, the number of births of quadruplets and higher orders fell by 80 percent.

Unlike the overall birth rate in America, which is at one a steep decline of 30 yearsthis coinciding decline in the number of multiple births is considered a positive turn of events.

It is a response to rapid advances in fertility treatments and the increasing age at which people choose to have children.

The very first ‘test tube baby’ was born in 1978 via in vitro fertilization (IVF), and in the 1980s and 1990s, when success rates were low, routine practice in many countries to transfer multiple fertilized eggs to increase the chance of pregnancy.

Thus began a dramatic increase in the number of multiple pregnancies that comes with it greater risks of death and illness for both mother and offspring, including preeclampsia, pre-eclampsia diabetespostpartum hemorrhage and low birth weight. Those are triplets almost certainly being born prematurely.

In 1997, a study found that the risk of a triplet from transferring three embryos during IVF was about 7.5 percent, which is what the authors thought at the time.unacceptably high“.

Transferring only one or two embryos prevents such adverse consequences. That’s why early 2000sThe American Society for Reproductive Medicine (ASRM) recommended that no more than two embryos be transferred to patients under the age of 35. Their goal was to eliminate quadruplets and limit triplets to below 2 percent of IVF cases.

There is no national law in the US limiting the number of embryos that can be transferred in a single IVF cycle, but assisted reproductive technology (ART) is one of the most highly regulated medical practices in the country, and most providers appear to require federal guidelines and state regulations to follow.

Data from Great Britain estimates the average IVF pregnancy rate The use of frozen embryos has increased from 7 percent in the 1990s to 36 percent in 2021, impacting the risk-benefit ratio for multiple transfers.

Between 1998 and 2011 studies show that during IVF in the US there was a 70 percent reduction in the transfer of three or more embryos.

The new CDC report shows that from 2009, there was a 52 percent decline in multiple births of triplets or more in the US. Among white women, who have the most access to IVF in the U.S., the number of births of triplets or higher order fell by 62 percent over the same period.

“If you look at the CDC numbers, you can see that these declines occur every year or two after these guidelines are updated,” says Micah Hill, president of the Society for Assisted Reproductive Technology. told CNN.

“These guidelines have evolved as technology has developed,” added Hill, who was not involved in the CDC report. “I think it’s been successful in making fertility treatments safer, and that’s really what we care about when we talk about reducing these higher order multiples.”

From 2020 more than 80 percent of embryo transfers in the US only involves one embryo.

ASRM researchers have advised to improve that number even further expansion of insurance coverage in the US to fertility problems.

IIf someone cannot afford multiple IVF procedures, patients and healthcare providers may face greater temptation to transfer multiple embryos to increase their chances of pregnancy, even if doing so increases the associated risks.

The CDC report can be read here.