 News
25th May 2006
IVF link to placenta previa
IVF may increase the risk of a potentially dangerous complication
of pregnancy.
A Norwegian study has found that the risk of placenta previa
rose from about three in 1,000 pregnancies in the general population,
to 16 in 1,000 for women who had had IVF.
The condition in which the placenta covers part or all of
the cervix, can block a baby's passage into the birth canal and cause
haemorrhaging in the mother, and increases the risk of a premature birth.
Several small studies have already suggested that placenta
praevia is more common after the use of assisted fertility techniques
but this study was on a much larger scale, using data on over 845,300
pregnancies.
The study, by a team at St Olavs University Hospital, in
Trondheim, also found a three-fold higher risk among mothers who had had
two pregnancies, once conceiving naturally and once with assistance through
IVF, or ICSI, in which a sperm is injected directly into an egg.
Lead researcher Dr Liv Bente Romundstad focused on the 1,349
women in the study who had conceived spontaneously in one pregnancy and
after assisted fertility in the other.
"Regardless of whether it was the first or second pregnancy
that was conceived through assisted reproductive technology, we found
a nearly three-fold higher risk of placenta praevia.
"This suggests that a substantial proportion of the extra
risk may be attributable directly to factors relating to the reproduction
technology."
Although the reasons for placenta previa are not clear,
it is thought that IVF may trigger contractions, leading to embryos implanting
lower down the uterus than in natural conceptions.
Alternatively, doctors may position the embryo lower down
the uterus in order to improve implantation rates.
Dr Peter Bromwich, from the Care fertility clinic in Northampton,
described the study as "fascinating".
"I have not come across this suggestion before. I already
do measure the position of transferred embryos, but I will start to record
it too now."
However, he added, "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 Mark Hamilton, chairman of the British Fertility Society,
said, "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."
The Human Fertilisation and Embryology Authority said the
research would be carefully considered by its Scientific and Clinical
Advances Group.
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