Can anyone shed some light on the sex during pregnancy topic. Some people say no, others say yes, others say only in the second & third trimester.......what's safe?

Also, is it a wives tale that sneezing is bad for the baby and can cause m/c?
I know that if I do sneeze the contraction of my abdominals sometimes causes a twinge in the ovary region that feels wrong. Is that someting to worry about or are little bubbas more resilient than that??