She might have had a difficult pregnancy, or had a lot of complicated personal things going on at the time (like maybe job loss or splitting with her husband or something) and hasn't been talking to anyone really. If that's the case I wouldn't take it personally, and I *definitely* wouldn't take it personally if she doesn't reach out much the first year or so of her baby's life. Having a baby is beyond exhausting, and most days she'll be lucky if she gets a shower much less time to call an old friend.
If you want to maintain your friendship, send your friend a note of congratulations and buy a baby gift. Whether you take it by yourself or have it mailed is up to you. Then be patient, she has a lot on her plate right now. She may reach out and start being more social again once her baby is a little older, or she might not, but if she's important to you and you want to keep the friendship then you should be the one willing to reach out and stay in touch and remind her that you're thinking about her, even if you don't get a lot back for a while. Someday the tables may be turned and YOU are the one overwhelmed with life events, but reassured by the fact that your friends are still there and still care about you.