Table 2.

Main advantages and weaknesses of the two control groups

	Advantages	Weaknesses
Control Group A (sperm donators & fertile partners of infertile woman)	- Direct access to the subject (face to face recruitment & blood sampling)	- Older than cases/difficult to recruit subjects below 25 years old
	- More concerned by the topic/good participation rate	- Live with infertile woman/more exposed to reproductive toxicant than general population?
	- Sperm count available
	- Regional recruitment
Control Group B (partners of pregnant woman hospitalized for pathological pregnancy)	- Same age group than cases	- More difficult to approach (visit during evening/week-end)
	- Direct access to the subject (face to face recruitment & blood sampling)
	- Presumably fecund	- No available serologies (need to store blood samples in separate areas)
	- Regional recruitment	- Link between subjects’ exposures partners’ pathological pregnancy?
	- Large population/easy to match with cases