It is usual for an egg and sperm to meet and for conception to begin in a fallopian tube. Normally the fertilised egg continues its journey into the uterus but in an ectopic pregnancy, the fertilised egg stays inside the fallopian tube.

The uterus is able to stretch and grow with the pregnancy. The fallopian tube cannot grow and expand in the same way, so an ectopic pregnancy cannot continue to develop. As the pregnancy becomes larger it stretches the tube, which is very painful and can cause the tube to tear or burst. If this happens there can be serious internal bleeding and urgent surgery may be needed.

Sometimes an ectopic pregnancy will shrink on its own and miscarry.

About one or two in every one hundred pregnancies are ectopic. Often no reason is found, but tubal pregnancy is more common in the following situations:

• after fertility treatment such as in-vitro fertilisation (IVF)
• if there is a history of pelvic infection
• in women with damaged fallopian tubes
• in women who have had previous surgery (such as caesarean section, ovarian cysts or appendix removed)
• in women who become pregnant while using an IUD or a progestogen only pill.