©Pregnancy bliss 2008
Ectopic pregnancy
An ectopic pregnancy is a pregnancy that implants outside the uterine cavity. The most common ectopic site is in the fallopian tube. It could, however, occur elsewhere such as in the cervix, ovary or pelvic cavity. Our discussion here will focus on the fallopian tube ectopic pregnancy, which accounts for well over 95 per cent of all ectopic pregnancies.
In the USA, roughly one out of every 100 pregnancies is ectopic. In the UK, the rate is 1 in 300. After the rate had doubled and even tripled in some countries in the 1970s and 80s, it started steadily falling. Now, there is evidence that rates in most of the western world are going up again.
Causes of ectopic pregnancy
Causes are not always apparent but previous infection is an important predisposing factor.
Pelvic infection, especially if there is delay in treatment, causes tubal damage. The residual scarring inside the tube may impede transportation of the fertilized egg towards the womb. This may lead to ectopic implantation. Chlamydia infection is particularly implicated, especially since it can be an entirely silent infection.
It is estimated that around a third (33%) of all ectopic pregnancies are a direct result of previous pelvic infection.
Other risk factors include surgery on the tubes (sterilization and reversal of sterilization) and some methods of assisted conception.
Cigarette smoking and ectopic pregnancy
There is strong evidence that smoking is a risk factor for ectopic pregnancy. In fact, it is believed to be the second most important factor after pelvic infection. Some experts have suggested that it might actually be the most important risk factor.
Ectopic pregnancy in the fallopian tube
The fallopian tube is the site of the vast majority of ectopic pregnancies but they could implant elsewhere in the pelvic and abdominal cavities
Smoking has been heavily implicated in ectopic pregnancy. It is second only to pelvic infection as a risk factor