The risks of complications both during pregnancy and at delivery are significantly higher for babies conceived through in vitro fertilization than by natural conception, finds a review published in this week's edition of The Lancet.
In vitro fertilization (IVF) has been performed for nearly 30 years. In developed countries, at least one per cent of births are now from assisted reproductive techniques (ART), so these children now represent a substantial portion of the population, the authors note. Yet little is known about the health of these babies.
The researchers led by Dr Alastair Sutcliffe, of the University College London, and Dr Michael Ludwig, Endokrinologikum in Hamburg, Germany reviewed data published between 1980 and 2005 on babies born by either IVF alone or by intracytoplasmic sperm injection (ICSI) and IVF, and used 3,980 articles to compile their analysis.
They focused mainly on IVF single births, since multiple births can bring their own set of complications.
They found that compared to those spontaneously conceiving, with IVF pregnancies:
- The rate of spontaneous abortion was increased by 20 to 34 per cent
- The risk of pre-eclampsia was increased by 55 per cent,
- The risk of stillbirth was increased by 155 per cent,
- The risk of low birthweight was increased by 70 to 77 per cent
- The risk of very low birthweight was increased by 170 to 200 per cent
- The risk of the baby being small for gestational age was increased by 40 to 60 per cent
Risk of major malformations was 30 per cent higher in babies born to couples using IVF -- although the absolute risk was still small.
There was also a higher risk of cerebral palsy in children born through IVF.
This is partly because of the risk associated with increased premature birth and partly because some twin pregnancies undergo early in-utero loss, and this event is associated with an enhanced risk of cerebral palsy. The risk of cerebral palsy was lower if a single embryo is transferred, rather than multiple embryos.
The authors note that some of the increased risks may be due to the fact that couples using IVF are generally older. The complications can also be due to endocrine disorders, organic abnormalities and can depend on the degree of ovarian stimulation.
"Some of the risks to children born after ART do not arise as a result of the techniques but from the background biology of the subfertile couple," the authors conclude.
They also point out that, overall, the biggest risk for IVF is that of multiple births.
