Infertility Treatments: Uncovering New Risks
Single-Birth Babies Conceived With Assisted Reproduction More Likely to Be Born Premature
Jan. 22, 2004 - Babies conceived via assisted reproduction are more likely to be born prematurely as babies conceived naturally, but this is less so in twin pregnancies, a newly published report shows.
Although the overall risks of problems at birth is small for single babies conceived using infertility treatments, study investigators say couples who consider using assisted reproduction technology (ART) should still be told about it.
"Women undergoing assisted reproduction should be informed of the increased risk in (single-baby) pregnancies," lead author Frans M. Helmerhorst, MD, and colleagues wrote.
An ART expert contacted by WebMD says it is too soon for such a warning because the studies do not offer conclusive proof that treatment for infertility is directly linked to problems at birth.
"Anytime there is a concern about adverse outcomes it needs to be taken seriously," Society for Assisted Reproductive Technology spokesman and past-president Robert G. Brzyski, MD, PhD, says. "This is a potential risk that needs to be considered, but it should not be presented as fact."
Risk of Early Birth 2 to 3 Times Greater
The analysis included 25 studies comparing the birth outcomes of single and twin infants conceived with the aid of infertility treatments with those conceived with no help from modern medicine. In addition to premature delivery, single-birth pregnancies conceived through ART had a higher incidence of low birth weight, cesarean delivery, and death.
Specifically, the risk of being born very prematurely -- prior to 32 weeks of gestation -- was three times greater than normal for singletons conceived through assisted reproduction and twice as great for delivery prior to 37 weeks of gestation. A full-term pregnancy lasts about 40 weeks.
Singletons conceived through assisted reproduction were three times as likely to have very low birth weights (less than 3.3 pounds) and 1.7 times as likely to weigh less than 5.5 pounds. The risk of cesarean delivery was 1.5 times greater than normal, and the risk of stillbirth or death within the first month of life was 1.7 times greater than normal.
Twins Fare Better
For twins conceived through ART, the risks and complications associated with delivery were only slightly higher than for twins conceived naturally. The risk of stillbirth or newborn death was actually lower for babies conceived with assisted reproduction.
Overall, the risk for birth problems is much greater for twin deliveries than for pregnancies with one baby, and Helmerhorst tells WebMD that this could explain why no difference was seen between the twins conceived through assisted techniques or naturally.
"An (ART) twin pregnancy may be relatively advantaged compared with other twin gestations, but this is a poor consolation for the much greater risk of twin pregnancies overall," he wrote in the Jan. 24 issue of the British Medical Journal.
In addition, Helmerhorst and colleagues acknowledged that the studies they analyzed could have been influenced by the fact that ART pregnancies tend to be more closely watched than those that occur naturally. As a result, physicians may have been more likely to identify problems in ART pregnancies and deliver babies early.