Ectopic pregnancy

 

Ectopic pregnancy

Definition:

An ectopic pregnancy (EP) is defined as the implantation of a pregnancy outside the normal uterine cavity. Over 98% implant in the Fallopian tube. Rarely, ectopic pregnancies can implant in the interstitium of the tube, ovary, cervix, abdominal cavity or in caesarean section scars. A heterotopic pregnancy is the simultaneous development of two pregnancies: one within and one outside the uterine cavity.

Incidence and aetiology:

One in 80 pregnancies are ectopic. They account for 9–13% of maternal deaths in the Western world and 10–30% in low resource countries. The incidence of a heterotopic pregnancy in the general population is low (1:25,000–30,000), but significantly higher after in-vitro fertilization (IVF) treatment (1%) due to the transfer of two blastocysts.

 Aetiological factors for ectopic pregnancy:

• Fallopian tube damage due to pelvic infection (e.g. Chlamydia/Gonorrhoea), previous ectopic pregnancy and previous tubal surgery.

• Functional alterations in the Fallopian tube due to smoking and increased maternal age.

 • Additional risk factors include previous abdominal surgery (e.g. appendicectomy, caesarean section), subfertility, IVF, use of intrauterine contraceptive devices, endometriosis, conception on oral contraceptive/morning after pill.

Common locations of Ectopic pregnancy:

Ectopic pregnancy is a pregnancy in which the developing blastocyst becomes implanted at a site other than the endometrium of the uterine cavity. The most common extrauterine location is the fallopian tube, which accounts for 96 percent of all ectopic gestations.

 Clinical presentation of ectopic pregnancy:

1.     The majority of patients with an EP present with a subacute clinical picture of abdominal pain and/or vaginal bleeding in early pregnancy.

2.     Rarely, patients present very acutely with rupture of the EP and massive intraperitoneal bleeding.

3.     The free blood in the peritoneal cavity can cause diaphragmatic irritation and shoulder tip pain.

The diagnosis of ruptured ectopic pregnancy:

It is usually clear as they present with signs of an acute abdomen and hypovolaemic shock with a positive PT. It is, however, important to be aware that it is common for women to experience bleeding or abdominal pain with a viable intrauterine pregnancy.

Investigations of ectopic pregnancy:

 The following are useful investigations for the diagnosis of EP. Nonetheless, again, it is fundamentally important to assess the woman clinically (‘ABC’, abdominopelvic examination) in conjunction with the results of investigations to manage the patient.

• TVUSS: identification of an intrauterine pregnancy (intrauterine gestation sac, yolk sac +/− fetal pole) on TVUSS effectively excludes the possibility of an EP in most patients except in those patients with rare heterotopic pregnancy. A TVUSS showing an empty uterus with an adnexal mass has a sensitivity of 90% and specificity of 95% in the diagnosis of EP. The presence of moderate to significant free fluid during TVUSS is suggestive of a ruptured EP.

• Serum hCG: the serum hCG level almost doubles every 48 hours in a normally developing intrauterine pregnancy. In patients with EP, the rise of hCG is often suboptimal. However, hCG levels can vary widely in individuals and thus consecutive measurements 48 hours apart are often required for comparison purposes.

• Haemoglobin and ‘Group and Save’ (or cross-match if patient is severely compromised):

• measure to assess degree of intra-abdominal bleeding and rhesus status. Pregnancy of unknown location

 • In up to 40% of women with an EP the diagnosis is not made on first attendance and they are labelled as having a ‘pregnancy of unknown location’ (PUL).

 • A PUL is a working diagnosis defined as an empty uterus with no evidence of an adnexal mass on TVUSS (in a patient with a positive pregnancy test).

• The mainstay of investigation of a PUL is consecutive measurement of serum hCG concentrations.

An endometrial biopsy can occasionally be helpful when hCG levels are static. All PUL must be investigated to determine the location of the pregnancy.

Management

 An EP can be managed using an expectant, medical or a surgical approach, depending on clinical presentation and patient choice.

Expectant management of ectopic pregnancy:

 Expectant management is based on the assumption that a significant proportion of all EPs will resolve without any treatment. This option is suitable for patients who are haemodynamically stable and asymptomatic (and remain so). The patient requires serial hCG measurements until levels are undetectable.

Medical management of ectopic pregnancy:

Intramuscular methotrexate is a treatment option for patients with minimal symptoms, an adnexal mass <40 mm in diameter and a current serum hCG concentration under 3,000 IU/l. Methotrexate is a folic acid antagonist that inhibits deoxyribonucleic acid (DNA) synthesis, particularly affecting trophoblastic cells.

The dose of methotrexate is calculated based on the patient’s body surface area and is 50 mg/m2. After methotrexate treatment serum hCG is usually routinely measured on days 4, 7 and 11, then weekly thereafter until undetectable (levels need to fall by 15% between day 4 and 7, and continue to fall with

treatment). Medical treatment should therefore only be offered if facilities are present for regular followup visits. The few contraindications to medical treatment include: (1) chronic liver, renal or haematological disorder; (2) active infection; (3) immunodeficiency; and (4) breastfeeding. There aren also known side-effects such as stomatitis, conjunctivitis, gastrointestinal upset and photosensitive skin reaction, and about two-thirds of patients will suffer from non-specific abdominal pain. It is important to advise women to avoid sexual intercourse during treatment and to avoid conceiving for 3 months after methotrexate treatment because of the risk of teratogenicity. It is also important to advise them to avoid alcohol and prolonged exposure to sunlight during treatment.

Surgical management of ectopic pregnancy:

The standard surgical treatment approach is laparoscopy (Figure 5.3). Laparotomy is reserved for severely compromised patients or where there are no endoscopic facilities. The operation of choice is removal of the Fallopian tube and the EP within (salpingectomy), or in some cases a small opening can be made over the site of the EP and the EP extracted via this opening (salpingostomy). Salpingostomy is recommended only if the contralateral tube is absent or visibly damaged, and it is associated with a higher rate of subsequent EP. Pregnancy rates subsequently remain high if the contralateral tube is normal because the oocyte can be picked up by the ipsilateral or contralateral tube.