I never congratulate people when they tell me that they had a baby. I mean, come on, you got married, had sex, this was bound to happen, right? That's the natural progression of things, not an achievement. Now congratulating someone on getting married, that's sensible. You actually found someone who's actually willing to to marry you! Now that's an achievement.
But congratulating for making a baby? It reminds me of the emails I receive on work anniversaries. "Congratulations on successfully completing 3 years at XYZ". Oh gee, thanks, I totally did it myself. When somebody congrats me on a work anniversary, what I imagine they actually mean is, "Congrats for not getting fired this year", or, "Yet another year and you still couldn't find a better job, SHAME ON YOU!"