Grade 3 placentation: incidence and neonatal outcome.

Although ultrasonically detectable placental changes have been correlated with fetal maturity, the relative incidence of each placental grade at various gestational ages has not been known. During a one-year study period, placental grading was evaluated in 1709 scans performed at 27 weeks' gestation or after. At 40 weeks' gestation or beyond, only about 20% of placentas had extensive calcification (Grannum grade 3). Significant placental calcification was rarely seen before 37 weeks' gestation. Placental grading could not be used to predict postmaturity. The incidence of fetal distress in labor was found to be increased with postmaturity as well as with other pregnancy complications that give rise to premature placental senescence, rather than with grade 3 placentas per se.