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Table 3 Summary of number of exposed and unexposed pregnancies to be recruited per site

From: Assessment of the safety of antimalarial drug use during early pregnancy (ASAP): protocol for a multicenter prospective cohort study in Burkina Faso, Kenya and Mozambique

Sites Approximate Population Size Approximate Pregnancies per year Projected number of exposures per yeara Sample Size over 1 years of recruitmentb Ratio of exposed to unexposed
   Embryo sensitive period 6 weeks (exposure risk %) Fully documented Exposed Fully documented Unexposed  
Kenya 25,000 1085 3 % 14 458 1:30
Burkina Faso 30,000 1000 6 % 42 658 1:16
Mozambique 33,000 1000 6 % 42 658 1:16
Overall 88,000 3085   98 1768  
  1. aThis was based on a number of assumptions, as follows: 1) the average pregnancy is 266 days (38 weeks) from conception (280 days or 40 weeks from LMP), 2) the average number of treatments with ACTs in adults in the study areas is approximately 0.5 treatments per year (1 every 2 years), and 3) the total fertility rate is estimated at 5.5 [29]. Under these conditions, we estimated the probability that an embryo would encounter artemisinins inadvertently during the critical 42 day (6 weeks) period of its development (week 4 to week 9 inclusive, from conception) is about 6.0 %. In the absence of regular pregnancy testing to exclude early pregnancy, the potential ratio of exposed versus unexposed pregnant women is estimated at 1:16. Exposure risk will be lower for the Asembo site as some women will be detected early and will be counselled not to take ACTs in the first 3 months of pregnancy
  2. bEstimating that about 70 % of exposures can be documents reliably and followed up to pregnancy outcome