Clinicoplacental phenotypes vary with gestational age: an analysis by classical and clustering methods

As the patterns and frequency of maternal and clinical conditions and outcomes and gross and histological placental features and lesions vary with gestational age at delivery, we aimed to study the impact of these changes on the placental diagnosis, hoping to uncover potential novel clusters of gestational age-associated clinical and pathological diagnoses.

Retrospective statistical analysis of clinicoplacental database.

We analyzed 28 clinical (maternal and fetal) and 49 gross and microscopic placental variables from 3294 consecutively signed placentas received between 2001 and 2012, divided into three gestational age groups: 16-27 weeks, 697 cases; 28-36 weeks, 1365 cases; and 37+ weeks, in all 1232 cases.

Classical statistics by chi-squared and Fischer's tests, and the Ward agglomerative hierarchical clustering and multidimensional scaling techniques, were used.

The placental phenotypes clustered statistically significantly with severe preeclampsia in the second trimester; preterm premature rupture of membranes, placental abruption, and fetal growth restriction in the whole third trimester; and abnormally invasive placenta, thick meconium, maternal diabetes mellitus, and substance abuse in term pregnancies.

The applied statistical analyses made it possible to simultaneously compare the strength of clinicoplacental associations separately in three pregnancy intervals. Placental clinicopathological associations are strongest for the second trimester, i.e. severe preeclampsia and preterm ascending infection-related conditions, but were not significant for other pregnancy complications such as mild preeclampsia, chronic hypertension, diabetes mellitus, or umbilical cord compromise.