Is light marajuana use safe for a man trying to conceive? does it cause birth defects? is alcohol consumption safe for a man trying to conveive? does it cause birth defects? which of these two is considered safer?

A man gets a bit of pass on their contribution to conception. The negative drug effects on sperm would affect some but not all those created from stem cells & the healthiest unaffected fellows would swim better & are more likely to do the deed. Women are not that lucky, anything they inhale/ingest can cause problems in her eggs or a fetus. No research clears marijuana in either case or alcohol.