Placental Features of Late-Onset Adverse Pregnancy Outcome

Objective: Currently, no investigations reliably identify placental dysfunction in late pregnancy. To facilitate the development of such investigations we aimed to identify placental features that differ between normal and adverse outcome in late pregnancy in a group of pregnancies with reduced fetal movement.

Methods: Following third trimester presentation with reduced fetal movement (N = 100), placental structure ex vivo was measured. Placental function was then assessed in terms of (i) chorionic plate artery agonist responses and length-tension characteristics using wire myography and (ii) production and release of placentally derived hormones (by quantitative polymerase chain reaction and enzyme linked immunosorbant assay of villous tissue and explant conditioned culture medium).

Results: Placentas from pregnancies ending in adverse outcome (N = 23) were ~25% smaller in weight, volume, length, width and disc area (all p<0.0001) compared with those from normal outcome pregnancies. Villous and trophoblast areas were unchanged, but villous vascularity was reduced (median (interquartile range): adverse outcome 10 (10-12) vessels/mm2 vs. normal outcome 13 (12-15), p = 0.002). Adverse outcome pregnancy placental arteries were relatively insensitive to nitric oxide donated by sodium nitroprusside compared to normal outcome pregnancy placental arteries (50% Effective Concentration 30 (19-50) nM vs. 12 (6-24), p = 0.02). Adverse outcome pregnancy placental tissue contained less human chorionic gonadotrophin (20 (11-50) vs. 55 (24-102) mIU/mg, p = 0.007) and human placental lactogen (11 (6-14) vs. 27 (9-50) mg/mg, p = 0.006) and released more soluble fms-like tyrosine kinase-1 (21 (13-29) vs. 5 (2-15) ng/mg, p = 0.01) compared with normal outcome pregnancy placental tissue.

Conclusion: These data provide a description of the placental phenotype of adverse outcome in late pregnancy. Antenatal tests that accurately reflect elements of this phenotype may improve its prediction.