Dear Hecate -- Why don't you know many cheerful songs? There are hundreds and hundreds of them. Labor is no joke, and during a lot of it you won't feel like singing at all - but I wish I had sung love songs to my arriving babes. Like "You're in my heart, you're in my soul, you'll be my friend should I grow old..." The Incredible String Band, (Robin Williamson et al-- remember them?)I'm pretty sure it was, had a song in the 70s about how wonderful and amazing a baby is -- and it's floating just outside of my mental reach, taunting me. All I can catch is something about "you are so bright..." OK here it is: http://www.stud.ntnu.no/~bakkevol/isb/tam.html

You get brighter every day -- and every time I see you.
Scatter brightness in your way -- and you taught me how to love you.
(etc.)

There are a lot of wonderful children's songs, too. If you're smart enough to think about singing during childbirth, you'll have a massive number of songs to choose from. How about, "Hello, I love you, won't you tell me your name?"