Randomisation and masking
STIS
The comparison between IPTp with sulfadoxine–pyrimethamine and IPTp with dihydroartemisinin–piperaquine was open label. The use of azithromycin was placebo controlled to ensure masking between the two arms containing IPTp with dihydroartemisinin–piperaquine. Women were randomly assigned (1:1:1) to receive monthly IPTp with sulfadoxine–pyrimethamine (sulfadoxine–pyrimethamine group), monthly IPTp with dihydroartemisinin–piperaquine plus a single treatment course of placebo at enrolment (dihydroartemisinin–piperaquine group), or monthly IPTp with dihydroartemisinin–piperaquine combined with a single dose of azithromycin at enrolment (dihydroartemisinin–piperaquine plus azithromycin group). Randomisation sequences were computer generated centrally at LSTM by the study statistician (DW), using permuted block randomisation (block size of three), stratified by site and gravidity (first or second In addition, a subgroup of a third of all participants in each group and study site was selected randomly for additional assessments. These included serial ultrasound scans to assess fetal growth, and extra samples taken for the assessment of STIs and other RTIs in the third trimester. This was based on computer-generated lists prepared centrally by the statistician in Liverpool (DW) before the start of the study. The same statistician also prepared another computer-generated list to select 10% of participants in each group and study site for home visits to assess tolerance and adherence to study drugs administered at home. The information on whether the participant was eligible for these additional assessments and home visits was included in the same sealed envelopes as the study allocation.