Second Trimester: Doggy Style. Spice things up without going acrobatic. If you feel any ache in your back during this one, consider propping up. I know I have read everywhere not to be worried about having sex during pregnancy (and trust me I'm not) but I was reading some of the. Doggy style ' position safe during pregnancy?. Babycenter., Can the air thrust into the vagina from sex cause the same harm? doggie.