PREDICTING THE OUTCOME OF THREATENED MISCARRIAGE (2)

THE STUDY

It was a prospective longitudinal study. Women were recruited at 6-10 weeks gestational age, presenting with vaginal bleeding in the presence of a sonographically viable intra-uterine pregnancy. They were seen weekly for five weeks. At each visit, they completed a Visual Analogue Scale of pain and bleeding intensity scores.

A visual analogue scale is a measurement instrument used to assess how a patient scores their medical symptom across a scale from mild to severe; it is used to assess their perception of the symptom. Being unique to each respondent, it cannot be used to compare between subjects but it can be used to compare the patient’s responses at different times.

At the end of the 5 weeks, an ultrasound scan was used to assess the outcomes of the pregnancies.

Primary outcome – identify biomarkers with significant relationships to pregnancy outcome.

Secondary outcome – derive a Pregnancy Viability Index (PVI) this would be a measure of the likelihood of the pregnancy succeeding. 

Tertiary outcome – assess the positive predictive value (PPV) and negative predictive value (NPV) of the derived PVI.

The predictive values of a test are determined by the sensitivity and specificity of the test and of the characteristics of the population being tested. So a test with very good sensitivity (able to detect those with the disease) and very good specificity (able to rule out those without disease) will have high positive and negative predictive values.

Of the 117 women recruited, 112 completed the study. Of these, 22 went on to pregnancy demise while 90 had their pregnancies continue. All miscarriages happened within 28days of presentation.

The following factors had significant Odds Ratios (i.e. the odds that these factors featured highly in those that miscarried versus those that did not miscarry were statistically significant): History of subfertility (difficulty conceiving), the baseline bleeding score (as rated by the patients on the scale), the baseline crown-rump length (on ultrasound scan), baseline Progesterone and baseline hCG levels. 

Factors that did not have significant Odds Ratio included previous pregnancy termination, Hb level and number of previous pregnancies.

Following further statistical analysis, the two factors that retained significance were the baseline bleeding score (BS) and the serum hCG.

They derived a PVI = hCG/BS × 1.87 ×10 and a high PVI meant a resulting miscarriage.

The PPV of the PVI was 94% and the NPV was 77%.

Of course, more research with a larger number of participants is needed to trial this score and even maybe practical testing in the clinics with resulting case reports may help to prove if this index is useful. But imagine how much easier life would be if we could tell on time which women with bleeding in the first trimester would simply need reassurance or would need early targeted counselling.

REFERENCE

Adam K, Developing a robust model for predicting the outcome of pregnancies complicated by threatened miscarriage in the first trimester of pregnancy. Session 34, ESHRE Stockholm,  July 2011.