Techniques used in fertility treatments may increase the risk of a complication during pregnancy, Norwegian scientists said on Thursday.

They found what they believe is the first evidence to show that women who have conceived through in vitro fertilisation (IVF) are more likely to suffer from placenta praevia, a serious condition which can be dangerous for both mother and child.

“We found a six-fold higher risk of placenta praevia in women who had had fertility treatment than in those who had conceived spontaneously,” said Dr. Liv Bente Romundstad of St. Olavs University Hospital in Trondheim, Norway.

The results mean that the risk rose from about three in 1,000 births to 16 in 1,000 following assisted reproduction.

“Although the risk of placenta praevia is considerably higher with assisted reproduction it is still quite rare,” Romundstad added.

In women with the condition, the placenta, which provides nourishment and oxygen for the fetus, attaches to the lower part of the uterus and can block the passage to the birth canal. It can cause bleeding and hemorrhage in the mother and increase the need for a caesarean section birth.

Romundstad and her team studied 845,300 pregnancies recorded in the Norwegian Medical Birth Registry between 1988 and 2002. They compared placenta praevia in women who had IVF treatment and those who conceived naturally.

She said the findings, which are reported in the journal Human Reproduction, suggest that the additional risk is related to fertility treatment.

The researchers do not know the cause of the increased risk but they suspect that if the embryo is placed low in the uterus when it is transferred during IVF it could increase the risk of the condition.

Research has shown that placing the embryo low in the uterus can improve implantation rates, so fertility clinics may prefer it, according to the scientists.

They are urging fertility experts to monitor and record where the embryo is placed during the transfer to determine whether it has an impact on the risk of placenta praevia.

“We now routinely do this, but we need other centers worldwide to do this as well,” Romundstad added.