Alicia,

I can talk about this from two angles, both the mother of a premature, and a nurse in a tertiary care LDRP.  I can also present this from two different points of view, protocol-wise.

When my son was born 25 years ago, at 30 weeks gestation, the hospital he was transferred to (not being born in a high risk center) taught me to pump, and encouraged me to pump q 3-4 hours during the day time only.
Their rationale was to have my milk coming in according to the expected schedule the baby would be feeding on once he came home.  They were not expecting to give him solely EBM until such time.

I figured that if q 4 was good, q2 was better.  So I pumped q 2 during the day and through the night whenenver I woke up do to leaky breasts, which was also q2-3.  In addion, I spent every day at the hospital from about 10 a.m. to 8 p.m., feeding my son by gavage until he was able to bottle, and by bottle until they let him go to breast (at ten days).  (I was not yet a nurse, just most of the nurses taught me and encouraged me to do as much of his care as I could.)  Needless to say, I was producing gallons, and my milk was fed to two other babies as well, still having ample for my son in the hospital, and to store at home.

When the doctors are advising less than q 2-3 hour pumping on a premie, they are either thinking about mom's rest requirements, or still thinking about the needs of the discharge date.  They are not doctors, I think, who have kept up to date with lactation issues, or who understand the effects or prolactin and the lactation process in the first few days/weeks.

Now, at our hospital, we encourage moms of premies to start pumping as soon after birth as possible, and to pump q 2-3 hrs., round the clock, as much as possible.  We rush their first few drops of colostrum off to the nursery as soon as it comes out, in a 1 cc syringe if all they could do was squeeze out drops, to emphasize how important that liquid gold is.  We are not militant -- we do not force them.  We encourage them, we bring them the pumps without waiting for them to ask.  We say "it's time to pump."  If they plead tiredness, etc., we try to help them get better rest periods to facilitate more pumping.  Most moms and their families do cooperate.

From the cultures who are used to bottle feeding for the first few days anyway, "no milk for three days"  "mom needs three days rest" we agree that that has worked in their cultures for centuries, but all of the world now we are advocating, the sooner, the more often, the better.  Then we leave it to them to choose.

Let me make two comments about my own state of mind:

In terms of all breast-feeding moms, I used to agonize over each and everyone that delayed or didn't even start bottlefeeding.  In a hospital and city that has a very high start rate, and a fair continuation rate, I can no longer kill myself over the moms who really don't want to breastfeed.  I have enough work to do during my eight-hour day, helping the moms who want to breast-feed or who are on-the-fence, and for whom my attention may be the turning point.  The rest, I give the information, I bring the equipment or the offer of hands on help, I give encouragement and I go on to the next.

In terms of delaying pumping, I have remembered that everything I did for my son 25 years ago, did not start until he was 48 hours old.  The day he was born he was whisked to another hospital while I was still in the delivery room.  I did not see him until he was almost 24 hours old, and then I saw him for about 1/2 hour and collapsed at his isolette.  I came back to the hospital 24 hours later, and I was first taught to pump then.
Fortunately, he was still NPO, so he never got any ABM, to my knowledge.

So while the delay of 24-48 hours might have an affect in minimizing milk production, still, for most women, I believe, it can be overcome by frequent, regular pumping once mom does start.  Maybe we should let our moms of premies wait a day or two, especially those who had C-sections, high blood loss, or are extremely sick.   Especially if the baby still cannot even take what they produce.

As you see, I am not citing references.  The references I would look for, if I had a less cooperative hospital staff would be those that discuss lactogenesis, those that support pumping at the same rate the baby would be feeding now, and those that talk about the dangers of feeding any artifical milks in the meantime.

Sincerely, Chanita