Neonatal outcome in a randomized, controlled trial of low-dose aspirin in high-risk pregnancies

To determine the value of low-dose aspirin in high-risk pregnancies, and assess its impact on fetal growth, as well as on perinatal mortality and morbidity.

One hundred and eight women with singleton pregnancies were enrolled in a randomized, double-blind, placebo-controlled trial of 100 mg/day aspirin from 17 to 19 week gestation. Enrolment criteria included pre-existing chronic essential hypertension or renal disease, or a history of previous early, severe pre-eclampsia.

There were four stillbirths (all aspirin) and two neonatal deaths (both placebo), to yield respective perinatal mortality rates of 69/1000 and 40/1000 (P = 0.499). Liveborn infants in the aspirin group were significantly more mature (P = 0.017) and of heavier birthweight (P = 0.034) but had similar length (P = 0.091) and head circumference (P = 0.257). Fewer infants in the aspirin group were liveborn prematurely (5/54 vs 14/50; P = 0.016) or were of low birthweight (3/54 vs 9/50; P = 0.052). There were no significant between-group differences for standard deviation (Z) scores for weight, length or head circumference, or for skinfold thickness measurements. There was no significant difference in occurrence of low Apgar scores or in neonatal intensive care unit use between the groups.

Low-dose aspirin does not appear to have a significant effect on perinatal morbidity. The increase in weight at birth associated with low-dose aspirin therapy is due to prolongation of pregnancy rather than prevention of intra-uterine growth retardation.