Data from: Placental pathology findings in unexplained pregnancy losses

There are approximately 5 million pregnancies per year in the United
States, with 1 million ending in miscarriage (a loss occurring prior to 20
weeks of gestation) and over 20,000 ending in stillbirth at or beyond 20
weeks of gestation. As many as 50% of these losses are unexplained. Our
objective was to evaluate the efficacy of expanding the placental
pathology diagnostic categories to include the explicit categories of 1)
dysmorphic chorionic villi and 2) small placenta to decrease the
unexplained fraction. Using a clinical database of 1,256 previously
unexplained losses at 6–43 weeks of gestation, the most prevalent
abnormality associated with each loss was determined through examination
of its placental pathology slides. Of 1,256 cases analyzed from 922
patients, there were 878 (69.9%) miscarriages and 378 (30.1%) antepartum
stillbirths. We determined the pathologic diagnoses for 1,150/1,256
(91.6%) of the entire series, 777/878 (88.5%) of the miscarriages
(<20 weeks’ gestation), and 373/378 (98.7%) of the stillbirths (≥20
weeks’ gestation). The most common pathologic feature observed in
unexplained miscarriages was dysmorphic chorionic villi (757 cases;
86.2%), a marker associated with genetic abnormalities. The most common
pathologic feature observed in unexplained stillbirths was a small
placenta (128 cases; 33.9%). Our classification system reinforced the
utility of placental examination for elucidating potential mechanisms
behind pregnancy loss. The improved rate of diagnosis appeared to be the
result of filling a gap in previous pregnancy loss classification systems
via inclusion of the categories of dysmorphic chorionic villi and small
placenta.