diagnosis

Last reviewed 01/2018

The gravity of this condition warrants early diagnosis. With modern methods, diagnosis may be made within 6 weeks of amenorrhoea, and frequently whilst the mother has no symptoms. An awareness of risk factors helps to identify patients in whom early investigations may be warranted.

The result of a pregnancy test (urine beta HCG) is essential to help determine further management.

A transvaginal ultrasound is the preferred method of investigation (1).

• sensitivity of diagnosing ectopic pregnancies varies from 73 to 93%
• it may reveal viable or nonviable intrauterine pregnancies, ectopic pregnancies or no visible pregnancies (a pregnancy of unknown location)
• can identify intrauterine pregnancies longer than 5.5 weeks with almost 100% accuracy (2)

Laparoscopy allows direct visualisation of an ectopic pregnancy but may fail if the pregnancy is early and the gestational sac small. It is of little value in a ruptured ectopic pregnancy when the peritoneum is blood filled.

Aspiration through the posterior vaginal fornix into the pouch of Douglas may be of help in a ruptured ectopic pregnancy when free blood is present.

If the diagnosis is in doubt then serial serum beta hCG measurements are taken to distinguish between a potentially viable intrauterine gestation, a resolving spontaneous abortion, and an ectopic pregnancy (2).

• in normal pregnancies, this will double about every two days (1) - a 66% rise in beta-hCG every 48-hours can be seen in 85% of viable intrauterine pregnancies during the first 40 days of gestation (3)
• in abnormal pregnancies, intrauterine or ectopic, there is impaired beta hCG production and a prolonged doubling time (1) - a 66% rise in beta-hCG every 48-hours can be seen in 13% of ectopic pregnancies during the first 40 days of gestation (3)
• if the rise is less than 50% in 48 hours, it is almost always associated with a nonviable pregnancy (either intrauterine or extrauterine) (3)

A Group and Save sample is taken. This allows the maternal blood group to be ascertained (and hence the possibile requirement for anti-D) and allows blood to be cross-matched in cases of haemodynamic compromise.

Reference:

• (1) Ramakrishnan K, Scheid DC. Ectopic pregnancy: forget the "classic presentation" if you want to catch it sooner. J Fam Pract. 2006;55(5):388-95
• (2) Barnhart KT. Clinical practice. Ectopic pregnancy. N Engl J Med. 200923;361(4):379-87
• (3) Sau A, Hamilton-Fairley D. Nonsurgical diagnosis and management of ectopic pregnancy. The obstetrician & gynaecologist 2003;5:29-3