Obstetrics
Jaimey M. Pauli, MD, and John T. Repke, MD (Update, January 2013)
Evolving applications of first-trimester ultrasound
Ilan E. Timor-Tritsch, MD, and Simi K. Gupta, MD (December 2012)
Is the hCG discriminatory zone a reliable indicator of intrauterine or ectopic pregnancy?
Andrew M. Kaunitz, MD (Examining the Evidence, February 2012)
A few outliers don’t justify dismissing the hCG
discriminatory zone
(Comment & Controversy, April 2012)
It is not uncommon to see a patient in her first trimester who is experiencing abdominal pain or vaginal bleeding or both. At my institution, we use the beta human chorionic gonadotropin (ß-hCG) value in conjunction with transvaginal ultrasonography to determine whether the pregnancy is a viable intrauterine pregnancy, a missed spontaneous abortion, or an ectopic gestation. However, even a combination of modalities can be inconclusive, necessitating repeated ß-hCG measurements and several ultrasound images. For the patient, it can provoke considerable anxiety to be told to wait and see if the pregnancy will continue.
Testing will not distinguish ectopic from intrauterine gestations
In their meta-analysis, Verhaegen and colleagues focused on a single measurement of progesterone to predict the pregnancy outcome in women who experienced pain or bleeding, or both. In early pregnancy, progesterone is produced first by the corpus luteum, then by the placenta. It stands to reason that nonviable pregnancies would have a lower level.
Although measurement of the progesterone level will not help distinguish an ectopic gestation from an intrauterine pregnancy, it does help identify nonviable pregnancy. This study found that a progesterone level below 6 ng/mL excluded a viable pregnancy in 99.2% of cases. Measuring progesterone could be very helpful when the ß-hCG level is low and ultrasound imaging is inconclusive. Currently, we tell patients under these circumstances that we need more time to sort it all out—we need to establish a trend for the ß-hCG and repeat ultrasonography. However, if we added assessment of the progesterone level and it were less than 6 ng/mL, we would be able to determine with near certainty that the pregnancy is nonviable. As a result, we could provide patients with some certainty earlier than we would otherwise be able to, even if it were not the news they had hoped to hear.
When the serum progesterone level is higher than 6 ng/mL, it doesn’t guarantee a viable pregnancy. Rather, it leaves us about where we were without it—somewhat unsure as to how things will turn out.
Testing may save money in the long run
Another advantage of adding the assessment of progesterone level may be lowered costs. If the progesterone level is less than 6 ng/mL and we can determine with almost 100% assurance when a pregnancy is nonviable, we stand to save the costs associated with additional visits, imaging, and ß-hCG testing. The authors did not address this issue, but perhaps another study will look at it more closely.
When a patient presents with pain or vaginal bleeding, or both, in early pregnancy, and ß-hCG measurement and ultrasonographic imaging are inconclusive, a single measurement of the woman’s progesterone level can help determine whether the pregnancy is viable. Values below 6 ng/mL suggest, with almost 100% certainty, that the gestation is nonviable.
LINDA R. CHAMBLISS, MD, MPH
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