The relation of birthweight to histological appearances in vessels of the placental bed.

Biopsy of the placental bed was attempted at caesarean section in 109 patients: 77 consecutive and 32 selected because of the maternal or fetal condition. Forty-seven (44%) of these biopsies were from the placental bed and contained spiral arteries suitable for comment. Histological examination separated the patients into four groups: comprising 11 whose vessels showed normal physiological changes, 20 who showed inadequate physiological change, 12 with acute atherosis, and four with a mixed pattern. There was no relation between these changes and maternal age, parity, race or smoking habit, but no physiological change and atherosis were more common in association with maternal hypertension. Mean adjusted birthweight was greatest in those with physiological changes, less in those without physiological changes or the mixed pattern, and least in those with atherosis. The four patients in the mixed group did not have any unifying clinical characteristics.