I'm not sure if it'll have an effect on your overall supply but your milk will come in sooner and you wont get painfully engorged like the first time. The Braxton hicks contractions will get stronger when your nursing the closer you are to your due date.
I nursed my daughter through my pregnancy until she weaned herself after she turned two and I was 6 months. My milk changed and I guess she didn't like the taste. All in all, I had 3 month I didn't nurse. I haven't noticed my supply changed from the first time but my son is only 6 weeks old and wants to eat every 2 hrs.
I are both 28 Together:
12 years Married: 09/24/2011
BFP#1: January '12 - DD1 09/16/2012
Preterm labor 31 weeks. Monitored for Hellp and diagnosed with oligohydramnios July '12
BFP #2: 06/25 - EDD
03/05/15 MMC confirmed 8/1 - D&E 8/4 retained tissue discovered 8/20
BFP #3 11/24 - 12/15 Heartbeat detected - DD2 07/29/15