Placentas of small-for-dates infants: a small controlled series from Mexico City, Mexico.

Thirty-five placentas of small-for-dates infants were compared with control placentas of normally grown infants. They were small by weight, area, and volume and tended to have a marginal cord insertion; marginal cord insertion was associated with a thick cord, and central insertion, with a thin cord. When the two groups were compared, the first showed increased fibrinoid deposits and atherosis, more severe fetal abnormalities, and abnormal nutrition in the mother, together with a high incidence of preeclampsia. In the mothers of both groups, peak diastolic blood pressure was lower than that in the control group; additional factors leading to a probable reduction in placental blood flow were different in the two groups.