June 20, 2008 -- One in 100 U.S. babies was conceived in a test tube -- and half these babies were twins, triplets, or higher multiple births, the CDC reports.
The CDC's most recent data on in vitro fertilization or IVF covers the year 2005. The data come from 422 of the 475 U.S. medical centers that provide various forms of assisted reproduction technology to people with fertility problems.
The findings highlight a major issue for IVF: multiple births. Because IVF is expensive, and in 2005 had only a 35% chance of resulting in a live birth, doctors most often implant multiple embryos into a woman's womb. The result: In 2005, 49% of IVF babies came in multiple births.
While IVF led to 1% of births in 2005, it accounted for 16% of twins and 38% of triplets or higher multiples. That's a $1 billion health problem, the CDC calculates, because twins and higher multiples are at high risk of being born prematurely.
Preterm babies have more health problems than do full-term infants, and IVF babies are more than three times more likely to be preemies.
"Approximately 42% of assisted-reproduction-technology infants born in 2005 were preterm, compared with approximately 13% of preterm births in the general U.S. population," the CDC's Victoria Clay Wright, MPH, and colleagues note in their report.
Currently, there is a trend among fertility specialists to encourage single-embryo procedures. Wright and colleagues argue that these efforts to limit the number of embryos transferred in each procedure "should be continued and strengthened."
Single-embryo transfers in women under age 35 had a 43% chance of resulting in a live birth. That's only 10% less than the 53% live-birth rate for multiple-embryo transfers.
"The 10% increase in the live-birth rate was accompanied by a 41% increase in the risk for a multiple delivery," Wright and colleagues observe. They suggest that IVF success should be measured not only by whether the technique resulted in a live birth, but by whether the technique resulted in a singleton birth.
Fertility, Infertility, and In Vitro Fertilization
The report carries a number of other eyebrow-raising findings:
42% of IVF procedures result in a pregnancy; 35% result in a live birth.
The highest live-birth rate -- 52% -- comes from IVF procedures using freshly fertilized embryos from donor eggs.
The lowest live-birth rate -- 28% -- comes from IVF procedures using the patient's eggs and thawed embryos.
Low birth weight was seen in 9% of IVF single births, 57% of IVF twins, and 95% of IVF triplets or higher multiples.
Premature birth occurred in 15% of IVF single births, 66% of IVF twins, and 97% of IVF triplets or higher multiples.
11% of medical centers performing IVF procedures did not report data to the CDC as required by federal law.