TOG Release: Pregnancy Of Unknown Location

Main Category: Pregnancy / Obstetrics
Article Date: 12 Nov 2008 - 4:00 PST

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A new review article published in TOG: The Obstetrician and Gynaecologist, looks at one of the mysteries of early pregnancy: pregnancy of unknown location (PUL).

Whilst most pregnancies are obviously within the uterus, PUL is used to describe cases where, whilst there is a positive pregnancy test, there is no sign of a pregnancy inside or outside the uterus, on transvaginal ultrasound or even at laparoscopy. Up to 31% of women attending early pregnancy assessment centres have a PUL though the experience of the sonographer can reduce this to 10%.

The majority of PULs are at low risk of being ectopic (outside the uterus) in location. However, correct detection is essential as, even though at least 15% of ectopic pregnancies resolve spontaneously, there is no method of differentiating these from those that will develop eventually rupturing and putting the woman's life in danger.

Serum levels of hCG (pregnancy hormone) are used to help determine location: approximately 70% of women with ectopic pregnancy will have a rise in hCG that is slower than the minimum for normal pregnancy or a fall that is slower than the minimum for spontaneous miscarriage. However, 15% of normal pregnancies will have an abnormal doubling time. This can make differentiating a failing intrauterine pregnancy from a healthy intrauterine pregnancy from an ectopic pregnancy, very difficult.

Diagnosis of ectopic pregnancy on transvaginal ultrasound should be based on the positive detection of an extrauterine sac and indirect signs such as a complex adnexal mass or echogenic fluid. In combination, these methods have a 93.5 - 100% positive detection rate.

There are four possible outcomes of PUL: disappearance of the pregnancy (44-69% of cases); progression to confirmation of a normal intrauterine pregnancy (up to 75% develop into viable intrauterine pregnancies); ectopic pregnancy (8.1-42.8%); persisting PULs which account ultimately for 2% of cases and are defined as those where the hCG levels don't decrease, there are no signs of trophoblastic disease and the location of the pregnancy cannot be identified. Expectant management of PUL has been shown to be safe and effective in reducing the need for surgical intervention but does require several visits to an early pregnancy assessment unit.

The review also recommends that women with a 'presumed' complete miscarriage should be treated as PUL and their pregnancy hormone levels followed until they are zero to avoid these women having a potentially catastrophic internal haemorrhage. In the Confidential Enquiry into Maternal and Child Health 2000-2002, 11 out of 17 first trimester deaths were from ruptured ectopic pregnancies and one potentially avoidable death was in a woman with an empty uterus on ultrasound. This was interpreted as a complete miscarriage and death occurred three weeks later from a ruptured tubal pregnancy.

Haritha Sagili, Senior House Officer at Nobles Hospital, Isle of Man said, "Today, women are able to find out whether they are pregnant far earlier in their pregnancy. Therefore, many pregnancies of unknown location that, in the past, would have resolved naturally before they were identifiable, are now routinely detected."

"Many of these pregnancies will still resolve spontaneously and in light of this, conservative management results in lower rates of unnecessary intervention. However, the difficulty lies in determining which cases will not and, therefore, clinicians must be meticulous in their care of any woman with a diagnosis of PUL."

Professor Neil McClure, TOG editor-in-chief said, "One can't be too careful: ectopic pregnancy is a killer. However, no one wants to operate unnecessarily - just in case it might be an ectopic pregnancy: the secret is very careful assessment and water-tight review processes to ensure that patients are not lost from follow-up".

Notes

The Obstetrician & Gynaecologist (TOG) is published quarterly and is the Royal College of Obstetricans and Gynaecologists' (RCOG) medical journal for continuing professional development. TOG is an editorially independent, peer reviewed journal aimed at providing health professions with updated information about scientific, medical and clinical developments in the specialty of obstetrics and gynaecology.

A full copy of the article can be accessed at: http://www.rcog.org.uk/resources/public/pdf/224.pdf

Reference

Sagili H, Mohamed K: Pregnancy of unknown location: an evidence-based approach to management. The Obstetrician & Gynaecologist 2008;10: 224-30.

Royal College of Obstetricans and Gynaecologists'