M.C.
Hi D.,
During your pregnancy your body will start producing colostrum, the "pre-milk." Colostrum is very thin and watery and your body produces it in much smaller volume than actual breast milk. It is very beneficial to the babies during their early days of life because it carries a substantial amount of antibodies which help develop their immune systems.
I don't know when your triplets are due, but the milk will not come in until a few days after they are born--and you will know it! Your breasts will be rock-hard and HUGE (I'm talking three cup sizes bigger) and they will hurt like hell. This is called engorgement. It may be hard to nurse when they are engorged like that, but I always had success with wet, hot washcloths laid over my breasts. It helped to soften them up and allowed the milk to flow--that's why I am puzzled why your doctor would tell you hot showers interfere with milk production. With severe engorgement and clogged milk ducts, hot showers usually help.
I have heard that if the baby/babies are born prematurely (as many multiples are) the engorgement will not be as severe as if they are born full-term. I don't know exactly why or if it's 100% true, as both of my biological children were born full-term; something about hormonal changes that occur late in pregnancy which don't occur if you are still late in your second trimester or early in your third...I tried to find a good article to refer you to in a link, but I didn't have much success. So I apologize for that.
I would say once your babies are born you will learn how much milk your body is capable of producing. I have heard many success stories about moms successfully breastfeeding multiples, sometimes with the help of supplemental bottles along the way. You will find in time what works best for you and your babies to keep all four of you happy and healthy :)
Good luck,
M.