I would say from recent experience that pregnancy, labor and birth are the easy parts. It's the days, weeks, months and years afterwards that will really test your character.
My wife and I just had a baby. The pregnancy was anticipation, excitement, a little stress, a lot of waiting, but you're still baby-less.
Then they give birth, and it is absolutely amazing - it blew my mind.
Now it's a couple weeks later, and the stress has come on like a tidal wave. We're like walking zombies, total sleep deprivation, fighting about every little thing. The baby is cute all day and then stays up screaming all night, for no reason. I know, that's babies. The first few months are very stressful on a marriage. You will be tempted to blow it all off. Or you might be strong and stick there with her, support her. You have to support the baby and think of almost nothing else. You are locked down to the house and constantly feeding and monitoring. There are health scares and crises. You try to keep it alive. It's even harder for the mother because they might be breastfeeding and somehow always end up taking more responsiblity (maybe it's evolution) for the care.
If you decide you are going to be there for her, then be a 17 year old man and be there for her.
If you decide you can't deal once the baby is there, then do the right thing and seek professional guidance and support.
Do not leave her cold - that will haunt you forever.
It's tough man I know, but that's life.
Hope it helps