Table 3.

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

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

^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

^bEstimating that about 70 % of exposures can be documents reliably and followed up to pregnancy outcome