Administration of low-dose aspirin to mothers with small for gestational age fetuses and abnormal umbilical Doppler studies to increase birthweight: a randomised double-blind controlled trial

Objective To determine whether antenatal treatment (for greater than or equ al to 14 days) with 100 mg aspirin daily, given to mothers with small for g estational age fetuses and abnormal umbilical Doppler, will increase birthw eight. Design Randomised, double-blind placebo controlled trial. Setting A tertiary referral centre. Participants Ninety-nine women, of whom 65 were treated for greater than or equal to 14 days (32 with aspirin and 33 with placebo) and comprised the s tudy group. The entry criteria were: singleton pregnancy with ultrasound ev idence of a small for gestational age fetus (abdominal circumference < 10%) ; previous anatomy scan < 20 weeks and no evidence of fetal abnormality; ge station between 24 and 36 weeks; umbilical artery Doppler resistance index > 95% for gestation; no previous aspirin treatment in pregnancy; and no con tra-indication to aspirin treatment. Results The mean duration of treatment was 30 days for aspirin treated, and 29 for placebo. No difference was found in birthweight or other measures o f fetal growth or newborn morbidity between those treated with aspirin or p lacebo. Compliance, assessed by thromboxane B-2 analysis, showed almost com plete suppression of thromboxane B-2 in aspirin treated women. Conclusion Low-dose aspirin did not increase birthweight in pregnancies whe re the fetus has abnormal umbilical Doppler and is thought to be small for gestational age.