An ectopic pregnancy describes implantation of the products of conception outside of the endometrial cavity, most commonly in the fallopian tube (95 per cent). Other sites also include the cervix, ovary and abdominal cavity.
It occurs in around one in 90 pregnancies.
An ectopic pregnancy may also co-exist with intrauterine pregnancy, known as a heterotopic pregnancy.
Aetiology
Ectopic pregnancy remains the leading cause of pregnancy-related first trimester deaths in the UK. Its prevalence continues to rise because of increases in the incidence of the risk factors predisposing to ectopic pregnancy.1 It complicates around 1 per cent of all pregnancies.
Although around half of ectopic pregnancies occur spontaneously, there are risk factors for ectopic pregnancy (see box).
All contraceptives have been shown to be protective against ectopic pregnancy when compared with controls.
Where an IUD or progestogen-only oral contraceptives fails, the risk of a pregnancy being ectopic is greater than with other forms of contraception. Depot and implant contraception may not carry the same risks.
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Presentation
The clinical presentation of an ectopic pregnancy is very variable. A patient may be asymptomatic until rupture occurs.
It is therefore important to have a high index of suspicion. Around a third of ectopic pregnancies present before a period has been missed. A diagnosis of ectopic pregnancy should be considered in all women of child bearing age who present with abdominal pain.
Diagnosis
The most accurate method to detect a tubal pregnancy is by a transvaginal ultrasound. If the scan is inconclusive, then serial serum beta-hCG measurements are taken.
If levels are falling, suggesting a miscarriage, the measurements should be continued until they are below 20IU/l. However, if they are increasing, the rate of rise is noted as serum beta-hCG usually doubles every 48 hours in early intrauterine pregnancy, but less quickly in ectopic pregnancies.
A transvaginal ultrasound should be repeated when beta-hCG is >1,000IU/l. At this level an intrauterine pregnancy should be seen; if it cannot be, an ectopic pregnancy should be suspected. Ectopic pregnancies are usually visible when beta-hCG is >1,500IU/l.
Expectant management
Management of an ectopic pregnancy can be expectant, medical or surgical.
Spontaneous resolution of tubal ectopic pregnancies can occur as in many cases with no future problems. Expectant management is an option for clinically stable women with minimal symptoms.
Serum beta-hCG levels should be monitored every two to three days until <20IU/l and the risk of rupture has passed. Scans are often repeated weekly to demonstrate a reduction in the size of the tubal mass.
Around one quarter of women being managed in this way will need to have active treatment, however. This is necessary if symptoms occur, serum beta-hCG levels rise or levels start to plateau.
It is therefore essential that women undergoing expectant management are aware of the importance of follow up.
Medical management
Performing serial serum hCG measurements and transvaginal ultrasound examination leads to early detection of most ectopic pregnancies allowing medical treatment with methotrexate.2
Medical treatment of ectopic pregnancies is now more common and avoids the need for surgery. Usually IM methotrexate is given. Methotrexate prevents the growth of rapidly dividing cells by interfering with DNA synthesis. It has a success rate of 50-90 per cent.
Women who receive methotrexate need to be followed up for about 35 days. It is common for women to have pain on days three to seven, which is usually due to a tubal miscarriage.
A second dose of methotrexate is usually given if the beta-hCG level does not fall enough.
A repeat ultrasound is usually performed once the beta-hCG level returns to normal.
Women need to be advised that they should avoid becoming pregnant for three months after receiving methotrexate due to the possible teratogenic effects.
A recent Cochrane review has shown that a single dose IM methotrexate is significantly less successful than laparoscopic salpingostomy.3
Surgical management
Surgical treatment can be laparoscopic or open; salpingostomy or salpingectomy.
Laparoscopic surgery results in a shorter hospital stay, a quicker postoperative recovery time and a lower recurrent ectopic pregnancy rate compared with open surgery. However, open surgery is usually performed in patients with haemorrhagic shock.
The decision to perform a salpingectomy or salpingostomy will also depend on the size of the ectopic pregnancy and the degree of damage to the affected tube. No significant difference in subsequent intrauterine pregnancy rate has been shown with salpingostomy compared with salpingectomy. Salpingostomy is usually performed when there is contralateral tubal disease and a desire to preserve fertility.
Nonsensitised women who are rhesus negative with a confirmed or suspected ectopic pregnancy should receive anti-D immunoglobulin.
Prognosis
Following an ectopic pregnancy, around 10 per cent of women will have another ectopic pregnancy.
Although the methods used for the diagnosis and management of ectopic pregnancy have changed significantly over the past 20 years, the death rate remains largely unchanged at about 0.35 per 1,000 pregnancies. This reflects the speed at which complications can occur and how rapidly a patient can deteriorate.
- Dr Newson is a GP in the West Midlands
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References
1. Nama V, Manyonda I. Tubal ectopic pregnancy: diagnosis and management. Arch Gynecol Obstet 2009; 279(4): 443-53.
2. Agdi M, Tulandi T. Surgical treatment of ectopic pregnancy. Best Pract Res Clin Obstet Gynaecol 2009; 23(4): 519-27.
3. Hajenius PJ, Mol F, Mol BW et al. Interventions for tubal ectopic pregnancy. Cochrane Database Syst Rev 2007, Issue 1. Art No: CD000324.
