Don’t know why but I get up some mornings humming this song (orig version)…
What other songs are there that’s about Love + Pregnancy other than this one (lounge lizard version)?
All I Want to Do is Make Love to You, by Heart
Papa Don’t Preach, by Madonna
Billie Jean, by Michael Jackson 
Havin’ My Baby, Paul Anka, featuring the immortal lyrics:
It’s a little cheesy, but how about “Danny’s Song (Everything Will Bring a Chain of Love)” Written by Kenny Loggins, though the best known version was by Anne Murray.
Oh, and there’s also “Soliloquy,” from the Rodgers and Hammerstein musical Carousel. It’s about a man who’s found out he’s going to be a father. He starts out by boasting about all the cool, macho things he’ll do with his son… then changes tempo and mood, as he realizes the baby may be a girl and may need VERY different things from him (“You can have fun with a son, but you’ve got to be a FATHER to a girl”).
Perhaps the antithesis of …Havin’ My Baby
Brick
Ladies and Gents
I hereby presents…
BABY, the musical
These may not be exactly what you’re looking for, but…
“A Child is Coming” by Paul Kantner
“One’s On the Way” by Shel Silverstein (here performed by Loretta Lynn)
“Weird and Wonderful” by Colin Meloy is awesome.
Or even better - “She’s on Time!”
The Carpenters, “I Believe You”
Lest you Eat for Two.
Would “Folly” be a good baby name? I can see Natalie doing it.
Not exactly a love song, but some dysfunctional love and pregnancy (and abortion!) feature in Unwritten Law’s “Shoulda Known Better”. So allow me to submit another antithesis to the OP…
In the first verse:
And then the second verse:
I have never seen drunken buffalos make love but I kinda like the song as I’m a sucker for vibrator effect.
See folks, this is why non-descriptive YouTube links suck! 
Lightning Crashes by Live is about having a baby. And “placenter.” Ick.
Title, name of artist, even some cheesy '70s lyrics … how is that non-descriptive?
Don’t forget: This is Paul Anka, the Mozart of Rock and Roll!
Get out your handkerchiefs for this one:
http://grooveshark.com/#/s/Hair+Of+Spun+Gold+original+Worktape+/2qXTm9?src=5
There are also plenty of old standards like “Cider Through a Straw” and “Kisses Sweeter Than Wine” that deal with parenthood as the inevitable outcome of attraction. And when it comes to show tunes–yow!
How about an anti-pregnancy song, Loretta Lynn “The Pill”