New Test Helps Predict Viability of Pregnancy

A single progesterone measurement is a useful tool for predicting nonviable pregnancies after inconclusive ultrasound assessments in women who present with pain or bleeding early in their pregnancy, according to a new meta-analysis.1

The results of previous studies evaluating the accuracy of progesterone levels in predicting pregnancy viability have been conflicting. To help make sense of these findings, researchers analyzed 26 cohort studies involving 9436 women with a spontaneous pregnancy of less than 14 weeks of gestation to determine the accuracy with which a single progesterone measurement can discriminate between a viable and nonviable pregnancy. Nineteen of these studies were of women with only symptoms, and 7 studies included women with symptoms and inconclusive ultrasound assessments.

In patients with symptoms and ultrasound assessment, the predictive value of the progesterone test for a nonviable pregnancy had a pooled sensitivity of 74.6%, a specificity of 98.4%, a positive likelihood ratio of 45, and a negative likelihood ratio of 0.26. The median prevalence of a nonviable pregnancy in these patients was 73.2%. If the progesterone level was lower than the cutoff value of 3.2 ng/mL, the probability of a nonviable pregnancy increased to 99.2%, from 44.8% when a high progesterone cutoff value was used. However, the predictive accuracy of low progesterone levels for the diagnosis of ectopic pregnancy was extremely poor.

In women with pain or bleeding, the single progesterone test predicted a nonviable pregnancy with a pooled sensitivity of 66.5%, a specificity of 96.3%, a positive likelihood ratio of 18, and a negative likelihood ratio of 0.35. The median prevalence of a nonviable pregnancy was 62.9%. If the progesterone level was lower than 10 ng/mL, the probability increased to 96.8%, up from 37.2% when higher cutoff values were used. These results show that the progesterone test is more accurate when patients have both symptoms and inconclusive ultrasound results.

The authors determined that the median chance of an early-stage pregnancy being viable after inconclusive ultrasound assessments is 26.8%. Although a miscarriage or ectopic pregnancy would be the most likely diagnoses when women present with pain or bleeding early in pregnancy, serial serum beta-human chorionic gonadotropin (beta-hCG) level measurements are needed to differentiate the outcomes. However, there is up to a 19% chance that the pregnancy remains viable even when there is a rise in suboptimal beta-hCG levels.² Complementing the beta-hCG test with a serum progesterone measurement can help increase the diagnostic accuracy of pregnancy viability, suggest the authors.

Pertinent Points:
- A single progesterone measurement is a useful clinical tool for differentiating between a viable and nonviable pregnancy.
- In women with pain or bleeding early in their pregnancy in conjunction with inconclusive ultrasound results, a single low progesterone measurement can rule out a viable pregnancy.

References:

1. Verhaegen J, Gallos ID, van Mello NM, et al. Accuracy of single progesterone test to predict early pregnancy outcome in women with pain or bleeding: meta-analysis of cohort studies. BMJ. 2012;345:e6077 doi: 10.1136/bmj.e6077.
2. Kadar N, Caldwell BV, Romero R. A method of screening for ectopic pregnancy and its indications. Obstet Gynecol. 1981;58:162-166.