Milk Supply During Pregnancy for a Younger Baby

Do not supplement!!! You should be just fine until about your 8th month. Then your milk will change consistency and may taste different. At that time, your infant will let you know whether or not she will be continuing to nurse, or need other forms of nutrition.

Your supply will be consistent for a long time yet - so don't worry about it. Colostrum will not happen until after birth of newborn.

Check out www.kellymom.com, she talks about tandem nursing all the time and has had personal experience with it too.

You don't have to stop breastfeeding b/c you are pregnant. However you need to make sure that you are taking good care of yourself. You need to eat healthy foods drink tons of water and make sure you take your vitamins. I have heard that your supply may go down. However your 5 month old will be eating more solids soon and as your supply goes down you will probably be feeding her enough solids to remedy this. Check out the La Leche League website b/c they have good information about stuff like this. Congratulations on committing to feeding your older baby the best food possible.

I ran out of good milk at about 5 mos pregnant while nursing. I could tell because my son would suck me dry and still want more and I just didnt have it. I suppose you can really increase your calorie consumption and keep your milk up till the baby gets here and I dont know this for certain but since you are already lactating I dont think you will go through the colostrum stage again (provided you keep nursing).
If you are able to eat enough to keep your milk rich enough things will be fine. You will know if your child is still hungry and yes you will have to add a few things to his diet to make up for your lessened milk supply. I have read on here tho lot's of moms nurse through an entire pregnancy with no problems. You just have to eat enough and drink plenty of milk yourself to keep up your supply.
My kids were 11 mos apart. Since my milk got weak and dwindled my oldest went to formula at 6 mos of age. I nursed the second one till he was almost 3.

you might want to pump and freeze for later use as well.

I am currently seven months pregnant and we got pregnant when my daughter was six months old. My milk supply held up really well for the the first 5 months of my pregnancy. I made sure that I drank a lot (at least 10 glasses of water every day, plus 3- 4 glasses of milk plus plenty of protein). Oatmeal can also help keep your supply of ( at least that's the rumor!). I noticedmy supply decreasing around month 6 and now at month seven, I am only nursing her before bed and I doubt that she is getting more than 3 ounces. So, if you eat well and drink up, you probably have a least another 6 months of plentiful nursing and could maybe even go beyond that. BTW - I did start whole milk when dd was 11 months because I was worried about my supply.

Eventually your milk supply will decrease/stop and you will produce colostrum. Your baby will wean on his/her own. I was 2 months pregnant with my third child when I weaned my second daughter who was 3 years and 5 months at the time. I weaned, not because of supply issues, but because nursing her was painful. I say don't supplement until your milk supply no longer meets the demands of your baby and your baby will let you know. IF you can make it to her 12th month, you can always switch to whole milk and forgo formula altogether.

I got pregnant when my older son was 10 m/o and he nursed for about 3-4 months, when he quit (weaned in one day -- probably due to a combination of a runny nose making it hard to nurse and my milk changing flavor). I was still making milk at that time -- for a week afterward, I tried to get him to nurse, and was able to hand-express some (didn't try much; I was just curious if I was still making milk). He refused the breast, so I stopped trying after a week. At that point, he was 13 m/o, and I never felt the need to give him formula, because he was eating table food and able to drink regular cow's milk if necessary. [I'm not much on cow's milk for kids, but won't go into that; I do let my kids have it with some regularity, but in general think that cow's milk should go to cow babies not human babies ;-)]

Pamela's response below was excellent -- I'd send two flowers if I could! :-D Yes, check out resources on "tandem nursing," and kellymom is an *excellent* site.

I would only add that if you do need to supplement your supply, you can check out "Eats on Feets" (there's a facebook page for every state), and see if any moms in your area have extra breastmilk to donate.