I've always kept everything fully shaved, that's just my personal preference and I wouldn't change it for the benefit of anybody else (including midwives etc). If you normally keep things trimmed/shaved downstairs, it can get a bit trickier in the later stages of pregnancy when your belly gets in the way, but I never found it to be too much of a hassle, just a little extra effort (I found sitting down in the tub was more comfortable than reaching around under my huge belly lol). I don't think there's any harm in keeping it 'maintained' during pregnancy and birth, just as there is no damage done by keeping hair down there if that's your normal grooming habit. If something happens during labour and you require a c-sec, the medical team will shave what they need to, I have heard some people say their midwives/Ob preferred them NOT to shave or wax prior to due date in case of infection but that seems a bit strange to me. Like I said, I kept everything off (and would usually save my shaving day for the night before antenatal appts etc because I get ingrowns a few days after shaving and preferred everything to look nice, not all pimply and stubbly lol) for both pregnancies and labours (lol I actually shaved in between contx with DD2 because I was about to go to hospy to give birth and didn't want any unsightly patches lol) and never had a problem.
Ultimately, the choice is yours - no harm is done either way, if you shave normally then just be careful (ask DP to help out or use mirrors to get those tricky spots!) to save yourself any painful nicks, otherwise, just do whatever you normally do!