An ectopic pregnancy occurs when a fertilised egg implants outside of the womb. It is possible for the egg to implant in the cervix, abdomen and ovaries, but the majority takes place in the fallopian tubes.
An outline of ectopic pregnancy
In healthy pregnancies the fertilised egg implants in the womb lining, where there is ample space to grow and develop. Around one percent of pregnancies are ectopic, meaning that the egg implants outside the womb; ninety-eight percent of ectopic pregnancies involve the egg being implanted in the fallopian tubes.
In an ectopic pregnancy the egg does not arrive at the uterus (womb), and instead implants in the fallopian tubes. After implantation the embryo begins to burrow into the lining of the tubes, causing damage and usually bleeding. Many women believe bleeding to be a sign of miscarriage, but in the case of an ectopic pregnancy this results from a tubular abortion as the embryo is released out of the tubes. Pain associated with ectopic pregnancy is brought on by prostaglandins, which are released at the site of implantation. An ectopic pregnancy can be serious and potentially life-threatening, if bleeding is severe. In most cases heavy bleeding results from delayed diagnosis. If the egg is implanted in the proximal tube it may affect the Sampson artery, leading heavy bleeding more early than normal.
With ectopic pregnancies, around half resolve on their own without treatment (known as tubal abortions). In some cases surgery is required if, for example, the fallopian tube has split or there is a risk of rupture. Surgery may be carried out by means of keyhole surgery (laparoscopy) or open surgery (laparotomy). The introduction of a drug called methotrexate has reduced the number of women who require surgery.
What are the causes of an ectopic pregnancy?
The source of ectopic pregnancies is unknown. Once the egg has been fertilised it will make its way down the fallopian tubes into the womb. And, if after around nine days it has not reached the womb, it will implant in that location usually in the fallopian tubes. There have been suggestions of causes and certain hazards for ectopic pregnancy, including smoking, the mother’s age and damage to the fallopian tubes (caused before pregnancy).
Cilia damage and tube occlusion
Cilia are fine hair-like projections which help to carry the fertilised egg to the womb by means of the fallopian tubes. If the cilia are damaged or the fallopian tubes blocked, this is likely to result in an ectopic pregnancy. Women who have pelvic inflammatory disease (PID) have an elevated chance of ectopic pregnancy. This is due to a collection of scar tissue in the fallopian tubes causing harm to the cilia. If both tubes are blocked as a result of PID, it is unlikely that pregnancy will occur in the first place. If surgery is carried out to repair damage to the fallopian tubes, this makes pregnancy more likely but augments the possibility of ectopic pregnancy. Procedures such as tubal ligation and tubal cautery augment the chances of ectopic pregnancy, and the reversal of tubal sterilisation also heightens the risk. If you have experienced an ectopic pregnancy in the past, the risk of having another ectopic pregnancy will be higher.
Excessive production of progesterone and oestrogen
There is conjecture about the roles of hormones in ectopic pregnancy; however, no formal link has been established. Higher quantities of progesterone and oestrogen are linked with an increased likelihood of ectopic pregnancy, since the hormones slow the progression of the egg though the fallopian tubes. Conversely, this theory is contradicted by the fact that older women are more likely to have an ectopic pregnancy, despite having lower proportions of oestrogen and progesterone.
The role of intrauterine devices (IUDs)
It was thought that intrauterine devices increased the chance of ectopic pregnancy. But, although the devices are effective in preventing pregnancies, there is little evidence to support them increasing the chances of ectopic pregnancy. It is still advisable for all pregnancies conceived when using an IUD to be investigated thoroughly. The new IUD, which is hormone-based, has lower rates of pregnancy than sterilisation procedures for males and females.
There has been a suggestion that fertility treatment can augment the chances of ectopic pregnancy – but the risk is low. It is possible for IVF (in-vitro fertilisation) to result in ectopic pregnancy, but this is rare and early ultrasound scans will detect signs before the pregnancy poses a life-threatening risk.
Older women have a higher likelihood of ectopic pregnancy, and smoking has also been linked to an increased risk. Women who have come into contact with diethylstilbestrol (DES) in utero are up to three times more likely to have an ectopic pregnancy.
What are the signs of ectopic pregnancy?
The early signs of ectopic pregnancy are usually undetectable, or mild, and in most cases symptoms develop around 7 weeks after the previous period. In developing countries it is common for symptoms to present later.
Early symptoms of ectopic pregnancy:
- Pain: this is usually mild to begin with.
- Vaginal bleeding: bleeding is usually mild and it can be difficult to distinguish between bleeding caused by an ectopic pregnancy and that associated with an early miscarriage or implantation of a healthy embryo.
Women who have late ectopic pregnancies are likely to experience pain and bleeding, which will be both internal and vaginal. External bleeding is caused by decreased progesterone levels, while internal bleeding results from rupture of the affected fallopian tube. At this stage doctors must differentiate between ectopic pregnancy, miscarriage and the early stages of a healthy pregnancy. If a pregnancy test is positive it is very unlikely that the patient has pelvic inflammatory disease, as it is uncommon for women with an active PID infection to conceive. PID is the main misdiagnosis of ectopic pregnancy.
Internal bleeding of a severe level may result in the following symptoms:
- Pain in the abdomen, lower back and pelvis.
- Shoulder pain.
- Cramps in the pelvis, normally on one side.
- Pain that arrives suddenly and tends to get worse.
Symptoms of ectopic pregnancy can often be mistaken for appendicitis, gastrointestinal conditions and infections in the urinary system.
What is the diagnosis process for ectopic pregnancy?
Doctors should investigate the possibility of ectopic pregnancy in any woman who has a pregnancy test result that is positive, are sexually active and/or display symptoms like lower abdominal pain and abnormal bleeding. An abnormal increase in hCG (Human Chorionic Gonadotropin) levels (above 3000 IU/ml) can also point to an ectopic pregnancy. A detailed ultrasound scan displaying no sign of intrauterine (inside the womb) pregnancy, combined with an abnormal hCG test result, will indicate ectopic pregnancy. If the uterus is empty and the levels of hCG are abnormal, this may indicate ectopic pregnancy; however, it is possible that the pregnancy may be intrauterine but too small to appear on an ultrasound scan. If the results lead to uncertainty tests will be repeated after a few days.
If an ultrasound scan shows an empty gestational sac with a foetal heart this is considered a clear indication of ectopic pregnancy.
A laparotomy or laparoscopy may be performed to seek visual confirmation of an ectopic pregnancy. In some cases the fallopian tube can appear normal despite an ectopic pregnancy. This is rare and only occurs during the very early stages of pregnancy.
Non-tubal ectopic pregnancy
Around 2 percent of ectopic pregnancies take place outside the fallopian tubes, when it is possible for the egg to implant in the ovaries, abdomen or cervix. A transvaginal ultrasound scan is usually used to diagnose a cervical ectopic pregnancy, and a test called Spiegelberg criteria is used to diagnose an ovarian ectopic pregnancy.
In rare cases it is possible to save an abdominal ectopic pregnancy. This is because the placenta is located on the abdominal organs and is able to get sufficient blood supply. In this case the foetus would be delivered via surgery. The risk of both the mother and baby dying is high, however, as the removal of the placenta usually causes heavy bleeding at the point of attachment. If the placenta is connected to part of an organ able to be removed (for example, a portion of the bowel), the placenta and the part of the organ it is attached to will be removed together. This scenario is so rare that accurate data is unavailable.
Ectopic pregnancy treatment
- Non-surgical treatment: the use of a drug called methotrexate has lessened the necessity for surgery. If it is given early on in the pregnancy it can help to prevent the development of the embryo, resulting in the end of a pregnancy.
- Surgical treatment: if haemorrhaging has occurred and bleeding is ongoing, surgery may be required. However, around half ectopic pregnancies are tubal abortions, meaning that the body expels the embryo without the necessity of surgery. The decision to operate is often difficult; the surgeon will consider the benefits and risks, explaining these to the patient before they make a decision. Surgery may be carried out by means of a laparotomy or laparoscopy. The procedure may involve removing only the foetus (salpingostomy) or the foetus and the affected fallopian tube (known as salpingectomy).
Probability of future pregnancy following an ectopic pregnancy
The chance of pregnancy following an ectopic pregnancy is based on the state of the fallopian tubes. The success rate for future pregnancies varies widely, though the risk of a successful pregnancy will be decreased following an ectopic pregnancy. In some cases patients may choose IVF to become pregnant.
Complications associated with ectopic pregnancy
The main complication associated with ectopic pregnancy is rupture, which causes internal bleeding and potential shock; death is possible, but very rare.