German investigators claim they have produced "robust" evidence that ovarian stimulation for IVF does not influence the birthweight of resulting babies.
Singleton children conceived through IVF have lower birthweights, on average, than their naturally conceived counterparts, and it has been hypothesized that ovarian stimulation could be a cause.
To find out, Georg Griesinger (University Clinic of Schleswig-Holstein) and colleagues analyzed data from a national IVF registry with 65-70 percent coverage. They retrieved information for all IVF cycles in women aged 25-35 years who underwent ovarian stimulation and had a live, singleton birth (n = 32,416).
On multivariate regression, the baby's birthweight was significantly and independently predicted by each of maternal height, maternal weight, duration of infertility, and the number of embryos transferred.
However, none of the parameters of ovarian stimulation studied-including duration of stimulation, use of gonadotrophins, and the number of oocytes retrieved-significantly predicted birthweight.
"The present study provides robust evidence from a large sample of IVF singletons that ovarian stimulation and birthweight have no apparent quantitative (eg, dose-response) association," say the researchers.
However, they caution: "Although this is reassuring to the clinician, it does not invalidate the need for studying the effect of ovarian stimulation on outcomes other than birthweight, such as epigenetic alterations, and associated health disorders."
Source: Human Reproduction 2008; Advance online publication
