It has been known for some time that there was an increased risk that a baby conceived through IVF (in-vitro fertilisation, in which sperm and eggs are mixed in a test tube) or ICSI (in which the sperm is injected into the egg) would be stillborn. But previous studies have not been able to show the scale of baby deaths.
Researchers say women contemplating fertility treatment should not be unduly anxious. Kirsten Wisborg, who led the study, said: “The risk of stillbirth is still very low after IVF/ICSI. We do not know whether increased risk is due to the fertility treatment or to factors pertaining to couples who undergo IVF/ICSI.” The fourfold difference was between women who had either IVF or ICSI and women who conceived either naturally or through other methods such as taking hormones to stimulate their egg production or artificial insemination.
The study, published in the journal Human Reproduction, involved more than 20,000 singleton pregnancies in Aarhus, Denmark. Dr Wisborg and colleagues analysed data that has been kept on pregnant women between 1989 and 2006, who form the Aarhus Birth Cohort. They had a wealth of data on the pregnancies and outcomes, including how long it took the women to become pregnant, smoking and drinking habits, age and education.
Out of 20,166 first-time singleton pregnancies, 82% were conceived spontaneously within 12 months and 10% after more than a year of trying. Of the rest, 4% were conceived after IVF or ICSI and 4% after other forms of fertility treatment. There were 86 stillbirths, giving an overall risk of 4.3 per thousand pregnancies.
But the risk of stillbirths in women who had undergone IVF or ICSI was significantly higher, at 16.2 per thousand.
The stillbirth rate among women who had undergone other fertility treatment, such as hormone stimulation, was lowest, at 2.3 per thousand. Of those who became pregnant spontaneously within 12 months of trying it was 3.7 per thousand and among those who took more than a year to get pregnant it was 5.4 per thousand.
“There has been speculation that the increased risk of adverse outcomes, in assisted reproduction might be related to infertility. However, we found the risk was similar between sub-fertile couples, women who had conceived after non-IVF fertility treatment and fertile couples.
“This may indicate that the increased risk of stillbirth is not explained by infertility and may be due to other factors, such as the technology involved in IVF/ICSI or some physiological difference in couples that require IVF/ICSI.”
Copyright: Guardian News & Media 2010