My advice to you would be to watch your iron and continue with preg vitamins right the way through. A twin pregnancy can be very depleting on your reserves, plenty of water too.
Any undue tiredness, dark circles etc, ask for iron to be checked, I found I was anaemic throughout my twin pregnancy and felt like poo.
Also watch for piles, have some anusol in just in case. I found the extra weight I was carrying played havoc with my bum x