Basic Trope: A man helping a woman give birth, usually in an emergency situation.
Straight: Bob helps Alice deliver her baby.
Exaggerated: Bob is Squicked by the childbirth, and some complication arises that makes this birth more drawn out than he'd like it to be.
Downplayed: Alice is calm and collected and is perfectly capable of delivering without assistance. Bob is panicked and tries to help as much as he can but all Alice needs is just some privacy and hot water. She still thanks him for being a nice guy.
Bob is a doctor, nurse, EMT, etc.
Alice goes into labor, but Bob is the only one around besides her, and there's no way of getting medical help for whatever reason(s).
Alice is assisted by another woman (with or without medical training.)
Reconstructed: Bob gets over the Squick and does what needs to be done. And even without formal medical training, Bob manages to help the birth go smoothly. If complications arise, his quick thinking helps to avert problems.
Played For Laughs: Bob is making "EWWWW!!!!" faces while he helps Alice.
Played For Drama: The birth is very difficult, and Bob has no medical training.