In rare cases, if mom has certain types of inffectious diseases, this can be a problem because they can spread - but for most people not at all. In fact, it is completely normal for blood to be in the milk (especially with first-time moms) anyway (even with healthy nipples). You just don't always see it because it is in such small amounts.
It can make mom sore if the blood is there because of nipple cracking though, it can be painful for mom. There is an art to breast-feeding so that mom doesn't have to experience much of things like cracked nipples and it takes a bit of learning but here are some things mom can do to help prevent both:
- Make sure baby's mouth is all the way on when latching. To really get baby fully latched on, her mouth should be wide open and it will feel a bit like the breast is being shoved on her, but it helps her feed better too so don't be ginger about it. Really press her head onto the breast when in the process of latching. Now, if the baby seems to be having trouble breathing, you are probably pressing too hard, but most moms are too gentle about it. Baby sucking on only the nipple will lead to cracked and painful nipples though.
- Use a pillow or boppy to lift baby up so she is aligned with the breast properly. If she is too low it creates extra strain on mom's nipples, breasts and back.
- Use a moisturizer after pumping or nursing. They make moisturizers specifically for this that are thick and will stay put even under nursing pads, but also be safe for baby, but chapsticks like you use on lips will work too in a pinch. I really like lansinoh because it was easy to find, smooth and easy to put on and is mostly lanolin and natural.
- Use the right position for you and baby. The standard nursing hold that is always pictured is not the only way. I was surprised to learn how many different ways there are to hold baby while she is nursing. To avoide putting lots of pressure on one specific spot, a different hold might work while a cracked nipple heals. There were times when I found the football hold to be much more comfortable for me and still great for baby. Switching hold style occasionally just for the sake of switching things up also empties things differently and more fully too (at least in my experience).
- The book, "The Womanly Art of Breastfeeding" was a wonderful resource for me that I have since passed on to my sister (who passed it on to another one of our sisters) so I can't go look anything up in it for you at the moment, but it was the book I referred to most in those first weeks with baby and for those first weeks back at work. You might see if you can borrow it from a local library or friend if you don't want to buy it, but I really recommend your wife read through it - it will help.
For further information online, this article may be helpful to you as well.
If there are any further difficulties and you can hire a lactation consultant they can be super-helpful as well (our hospital provided one right after birth and for the first month free of charge so check if there is anything like that available to you as well). If that isn't an option, La Leche League is "womanned" with wonderfully sweet, supportive and helpful moms that have been through it too. They are fiercely in support of breastfeeding and the right to breastfeed without shame.