The researchers found that women face a slightly increased risk of ectopic pregnancies after IVF. More surprisingly, they found that whereas in the normal population the risk of an ectopic pregnancy increases with women's age, after IVF the risk decreases with age in women who have had diseased Fallopian tubes.
Elizabeth Asung, an honorary research fellow at Leeds University and The Bridge Centre in London, UK, told the annual conference of the European Society of Human Reproduction and Embryology that she had analysed data from the UK's Human Fertilization and Embryology Authority (HFEA) on 97,240 women, aged between 18-50 who underwent either straightforward IVF embryo transfer (IVF-ET) or embryo transfer after ICSI (ICSI-ET) between 1991 and 1999.
She and her colleagues found that after ICSI-ET the incidence of ectopic pregnancies was 1.3% – a figure that places it firmly in the range of incidence in the normal population. However, after IVF-ET the numbers increased by roughly a half from between 1-2% in the normal population to 2.8%.
Ms Asung said: "The difference in the numbers of ectopic pregnancies after IVF-ET and ICSI-ET may be because with ICSI the women tend to have no or fewer abnormalities associated with infertility because it's the man's fertility that is at issue. Whereas with IVF there's a higher proportion of women with compounding problems such as tubal disease, which may be contributing to their infertility and which are risk factors for ectopic pregnancies."
The study found that when women's Fallopian tubes had been damaged by tubal disease, the numbers of ectopic pregnancies increased to 6.1% in women under the age of 25, 4.1% between 25 and 29, 3.9% between 30 and 34, 3% between 35 and 39 and 2% in women aged over 40. Ms Asung said: "This makes tubal disease a significant risk factor for ectopic pregnancies after IVF-ET. However there is good news for women over 35 with tubal disease: these figures show a significant downward trend with age that we did not see with other indications for IVF treatment or following treatment with ICSI."
The question that remains unanswered is why the risk of ectopic pregnancies should decline with age in women with tubal disease. "There could be a number of explanations. It might be that the time elapsed between the tubal disease and IVF treatment was greater in older women and that perhaps the effects of the disease had started to recede. Or it could be to do with the fact that the transferred embryo is less likely to be washed up into the Fallopian tubes in older women. I really don't know, and this requires more research."
Ms Asung said that women needed to be aware that they might have an increased risk of an ectopic pregnancy if they have suffered from tubal disease. "In recent years we have seen an increase in ectopic pregnancy rates in all ages, but predominantly in younger women. This increase has been seen in many countries. In younger women the increase was five-fold between 1966 and 1996 in England and Wales, and the most likely explanation is the change in sexual practices during that period, which increased exposure to sexually transmitted diseases. Chlamydia trachomatis is the most common genital and urinary infection in women and the rate of exposure to this has increased four-fold from 1981 to 1986. The problem with Chlamydia is that in 90% of women it doesn't cause any symptoms, yet it is the commonest cause of tubal infertility and a significant cause of ectopic pregnancies. Most women with tubal disease in our study were aged between 25 and 34"
The study showed that endometriosis – another indication for fertility treatment – also appeared to be a risk factor for ectopic pregnancies after IVF-ET. Incidence rose to 2.3% in these women.
The researchers found that there was a small but significantly higher incidence of ectopic pregnancy when three embryos were transferred rather than two; incidence rose from 2.2% to 2.6%. "Presumably the greater the number of embryos transferred, the more likely the risk of implantation outside the uterus," said Ms Asung.
Abstract no: O-098 (Tuesday, 10.30 hrs CET, Europa room)
Notes
[1] An ectopic pregnancy occurs when the fertilized egg tries to establish a pregnancy outside the uterus, often in the Fallopian tubes. The pregnancy is unsustainable and it is a life-threatening condition for the woman.
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