Correct. They don&#x27;t prevent, they reduce. Used at typical rates, 18% of women will still get pregnant every year (reduced from 85% - it&#x27;s a large reduction, but I would not call it prevent).<p>For a situation like this, with (according to geertj&#x27;s calculations) 40% chance of severe birth defect, that&#x27;s far too much.<p>Condoms are not the solution here - in fact I think they do more harm than good because people think they work (like you did), while they are not sufficiently effective.