Single dose v two-dose antenatal anti-D prophylaxis: a randomised controlled trial

Objective: To compare rates of detectability of circulating Rh(D)-immunoglobulin (anti-D) at delivery with single and two-dose antenatal anti-D prophylaxis (RAADP) regimens; to compare compliance with the two regimens. Design: Open label, randomised controlled trial between May 2013 and November 2015. Setting, participants: 277 women who attended a tertiary obstetric referral hospital in Perth for antenatal care and were at least 18 years of age, less than 30 weeks pregnant and yet to receive RAADP, Rh(D)-negative (negative antibody screen), and who intended to deliver their baby at the hospital. Exclusion criteria were prior anti-D sensitisation, any contraindication of anti-D administration, and a history of isolated IgA deficiency. Interventions: One 1500 IU anti-D dose at 28 weeks of pregnancy (single dose regimen); two doses of 625 IU each at 28 and 34 weeks of pregnancy (two-dose regimen). Main outcome measures: The primary outcome was the proportion of women with detectable anti-D levels at delivery; the secondary outcome was compliance with the allocated RAADP regimen. Results: Circulating anti-D was detectable at delivery in a greater proportion of women in the two-dose group (111 of 129, 86%) than in the single dose group (70 of 125, 56%; P < 0.001). Compliance was not significantly different between the single dose (86 of 138, 61%) and two-dose groups (70 of 139, 50%; P = 0.06). Conclusions: The two-dose RAADP schedule currently recommended in Australia provides better protection against Rh(D) sensitisation than a one-dose regimen. Trial registration: Australian and New Zealand Clinical Trials Registry (ACTRN12613000661774).