The rate of ectopic pregnancies in the UK following assisted reproduction has almost halved in the past 12 years, according to a new analysis.
The study, which was presented at the annual meeting of the European Society of Human Reproduction and Embryology in Lisbon, Portugal, looked at every one of the 161,967 pregnancies that resulted from IVF, ICSI and IUI in the UK from 2000 to 2012. It revealed that the rate of ectopic pregnancies fell from 20 cases per 1000 to 12 cases per 1000 during those 12 years.
Lead researcher Professor Nikolaos Polyzos of Vrije Universiteit in Brussels, Belgium, said that the reduction in risk 'appears strictly associated with the reduction in the incidence of tubal factor infertility and the transfer of fewer embryos'.
Ectopic pregnancy, in which the embryo implants in the fallopian tubes instead of the uterus, is a life-threatening condition. There are around 11,800 cases per year in the UK - an average of 11 cases per 1000 pregnancies overall. Although it is known that the rate is higher following assisted reproduction, it had not been clear why.
Looking at the data - which came from the national database of the UK's Human Fertilisation and Embryology Authority (HFEA) - two major risk factors emerged. The first was having a diagnosis of a fallopian tube problem, which more than doubled the risk of an ectopic pregnancy. The second was having multiple embryos transferred, which increased the risk by around 30 percent for each additional embryo implanted.
The HFEA database showed that the proportion of infertile patients with tubal disease has progressively decreased, from 24 percent in 2000 to 12 percent in 2012. Tubal disease is usually caused by infection with chlamydia, and Professor Polyzos praised the UK's National Chlamydia Screening Programme, which has been in place since 2003, for its role in reducing the rate of the disease.
The data also showed that transferring embryos at 3 to 5 days old resulted in lower rates of ectopic pregnancy compared to transferring them at 1 or 2 days old.
There has been a shift in recent years toward implanting fewer embryos and implanting them later, as well as removing diseased fallopian tubes prior to IVF, said Stuart Lavery, a consultant gynaecologist at Hammersmith Hospital who was not involved in the study. 'When couples are having IVF, ectopic pregnancy is just not on their radar, so when it happens it is a real shock,' he said. 'This decrease in the rate of ectopic pregnancy is an expected one but also a welcome one, especially as it's so dramatic.'
Although there were no details of patients' smoking habits, smokers are known to have twice the risk of ectopic pregnancy as non-smokers. 'As nationwide anti-smoking campaigns have been implemented in the UK over the last decade with very high success rates, it is highly likely that the reduction in smoking would have had a substantial impact on the progressive decrease in the incidence of ectopic pregnancy over time,' said Professor Polyzos.