Pregnancy Of Unknown Location
An article published in TOG: The Obstetrician and Gynaecologist, speaks of a type of pregnancy which continues to mystify: the pregnancy of unknown location (PUL). The vast majority of pregnancies are located in the uterus. But PUL describes the case in which a woman has a positive result on a pregnancy test, but a physician can find no signs of the pregnancy either inside of or outside of the uterus. Neither transvaginal ultrasound nor laparoscopy will turn up any evidence of a pregnancy. PUL occurs in 31% of women who seek early prenatal care, though a good sonographer can reduce this statistic to a mere 10%.
Most PUL's don't turn out to be ectopic pregnancies (located outside of the uterus). But since a minority of these pregnancies are ectopic, they must be identified in time to prevent serious injury. While 15% of all ectopic pregnancies resolve on their own, it's impossible to know which ectopic pregnancies will be the kind that rupture and threaten a woman's life.
The location of the pregnancy can sometimes be determined through blood levels of the pregnancy hormone known as hCG. In 70% of ectopic pregnancies, it takes longer for hCG levels to crest than what is experienced in a healthy pregnancy, while levels of hCG will fall at a more gradual pace than is seen with a miscarriage.
But this method of detection is not perfect since 15% of healthy pregnancies double hCG levels in an unpredictable manner. This makes it difficult to differentiate the failed pregnancy, the healthy pregnancy, and the ectopic pregnancy.
PUL is resolved in one of four ways: the pregnancy disappears (44%-69%), there is eventual confirmation of an intrauterine pregnancy (75%), ectopic pregnancy is confirmed (8.1%-42.8%), the PUL persists (2%). Doctors manage PUL's by testing and retesting and the patient will need to make many visits to the clinic. But a watch and wait method avoids surgical intervention much of the time.
The article also states that all women who are presumed to have had a complete miscarriage should receive care as if they were PUL patients. This means that levels of hCG should be tested until the number reaches zero to prevent a possible hemorrhage from a ruptured ectopic pregnancy.
According to the Confidential Enquiry into Maternal and Child Health 2000-2002, 11 in 17 early pregnancy maternal deaths were due to the rupture of an ectopic pregnancy. One of these women was found to have an empty uterus during ultrasound. It is possible her death might have been avoided. She was diagnosed as having had a complete miscarriage, but died three weeks later due to a ruptured ectopic pregnancy.