Yes, this is an actual discussion happening at my house today. There were strong opinions shared and someone yelled, "Look, no vagina!"
However, we did some polling and got suggestions from others. Do mermaids give birth to live young or lay eggs? Do mermen carry the babies like male seahorses? But mermaids have breasts so they must be mammals somewhat, even if they are fish from the waist below? We decided mermaids probably birth like dolphins? So here you go! A dolphin birth video.