IVF Risks Mostly Due to Multiple Births
Single-Embryo Transfer May Cut Risk of in Vitro Fertilization
July 26, 2007 -- In and of itself, IVF -- in vitro fertilization -- carries
only slight risks compared with natural conception, a new study suggests.
IVF does carry major risks, which include premature birth, low birth weight,
stillbirth, spontaneous abortion, preeclampsia, placenta previa, and, to a lesser extent,
birth defects and cerebral palsy.
What is responsible for these poor outcomes? To find out, Alastair G.
Sutcliffe, MD, of the Institute of Child Health at the University College
London, and Michael Ludwig, MD, of the Center for Hormonal and Metabolic
Illnesses in Hamburg, Germany, analyzed 30 years of data on IVF.
The main finding: Most IVF risks are due to multiple births, and not to the
IVF procedure itself. Twins, triplets, and other multiple-birth children are at
much higher risk of premature or low birth weight than are singleton children.
And premature birth and low birth weight are linked to a host of health
But even single children born via IVF have more health risks than do
naturally conceived children. Nearly all these risks, the researchers find, are
due to the same parental factors -- such as older age or genetic defects --
that make it difficult for a couple to conceive naturally.
"The things related to subfertility are probably the factors that result
in the subtle differences in children born via assisted reproduction technology
and children naturally conceived," Sutcliffe tells WebMD.
The findings closely mirror those of an expert panel convened in 2005 by the
U.S. National Institute of Child Health and Human Development. NICHD medical
officer Uma M. Reddy, MD, MPH, was lead author of the panel's report.
"The majority of problems we see with assisted reproductive technology
are multiple births," Reddy tells WebMD. "But even singletons have
higher risk of complications. But is it due to the procedure or to factors
related to infertility? More and more evidence suggests it is not due to the
In vitro fertilization doctors agree with this assessment, says George
Attia, MD, director of reproductive endocrinology and infertility at the
University of Miami Miller School of Medicine.
"Most of the risks don't arise from the technique, but from the
background biology of the couple," Attia tells WebMD. "Dr. Sutcliffe is
right on the spot."
Single-Embryo Transfer: Answer to IVF Risk?
In the U.S., doctors typically implant two or more embryos, which greatly
increases the chance of multiple births -- and greatly increases pregnancy
"The majority of the patients want three or four embryos to be
transferred," Attia says. "In the U.S., there is a different mentality.
Most of this is not covered by insurance, so they really want to get pregnant
on the first try and not have to do this several times. In Europe, where IVF is
mostly covered by national health services, there is much more stress on