Assisted reproduction increases risk of placenta disorder
Progress Educational Trust30 May 2006
Researchers at St Olav's University Hospital in Trondheim, Norway, have discovered a link between assisted reproduction and an increased risk of placenta praevia - a dangerous complication of pregnancy where the placenta covers all or part of the cervix. The condition normally affects around three in 1000 births, but with a single IVF or ICSI (intracytoplasmic sperm injection) conception the risk raises to 16 in 1000. The researchers also examined women who had one pregnancy conceived naturally and one conceived using assisted reproduction (ART), in this case the risk rose from around seven in 1000 for two natural conceptions to 20 in 1000 for one ART and one natural; it did not make a difference which pregnancy was through assisted reproduction. This helps to rule out the possibility that there was some maternal factor in the single ART pregnancies which could cloud the findings.
The study, published in advance online in Human Reproduction, looked at more than 845,000 cases between 1988 and 2002, and was designed to correct for factors such as maternal age. The underlying reasons for the increased risk are not clear although the team postulate that the position in which the embryos are placed into the womb in ART may be a factor. There is research that suggests conception rates are higher when the embryo is inserted lower down in the uterus - this is also thought to reduce the risk of ectopic pregnancy. The team are now calling on fertility clinics to record this extra data. Dr Liv Bente Romundstad, leader of the study, said 'we now routinely do this, but we need other centres worldwide to do this as well'. She added: 'Although the risk of placenta praevia is considerably higher with ART it is still quite rare, which means it will probably take several thousand pregnancies to get sufficient data to be able to make any definite recommendations about clinical practice'.
In the paper the researchers suggest that assisted reproduction techniques may induce uterine contractions after stimulation of the cervix, this may then lead to more embryos implanting low-down. If the placenta covers the whole of the cervix then the baby must be delivered by caesarean section. There is also an increased risk of bleeding or haemorrhage as the placenta is stretched during the final stages of pregnancy. Commenting for the BBC, Dr Peter Bromwich of the Care fertility clinic in Northampton, said the work was 'fascinating'. He did, however, note that 'placenta praevia is a rare condition, and the fact that it might be a little less rare in IVF pregnancies should not be a cause for concern for people having the treatment'.
Dr Romundstad said that 'regardless of whether it was the first or second pregnancy that was conceived through assisted reproductive technology, we found a nearly threefold higher risk of placenta praevia', adding that 'this suggests a substantial proportion of the extra risk may be attributable directly to factors relating to the reproduction technology'. In the light of the findings, Dr Mark Hamilton, chairman of the British Fertility Society, said that 'patients who are considering IVF treatment should discuss concerns with their gynaecologist in advance of treatment and those who are pregnant might want to discuss this with their obstetrician'.
Reproduced with permission from BioNews, an email and online sources of news, information and comment on assisted reproduction and genetics.