Citations and figures immediately, please, specifically relating to cousin marriage in those countries together with evidence that they “cause significantly higher birth defect rates...pulling the global rate up.”
I grew up in an impacted area; you might call it downwind of Chernobyl. My mother had thyroid cancer at a young age and now had no thyroid. Numerous female relatives as well as friends and acquaintances have experienced similar problems and those are all associated with Chernobyl.
Here’s a single scientific source. There are more, but I’m sure you’re eager to demonstrate your hypothesis that women in Eastern Europe are getting cancer not from industrial accidents but from cousin marriage.