What's wrong with your baby?

1. Absolutely nothing. Stop worrying.
2. At night it crawls to the highest point it can find and lies there, crooning softly. It won't stop or sleep until it can get there. If you try to stop it, it'll just keep butting it's head against any barriers until you remove them. On the d4th night, a black shape swoops down and takes it.
3. Its teeth are sharp. It leaves a ring of blood when it breastfeeds. It won't eat or drink anything but meat and blood.
4. It gets sick of hanging around the womb and eats its way out of you.
5. You can't cut the umbilical cord. The baby slowly drains your strength through it. Over a matter of days, you weaken as it becomes bigger, until you swap places and it nurtures you as its stunted child.
6. The baby is perfectly healthy, but its skin is always cold. It never makes a sound, just watches you constantly. If you leave it alone in a room, you come back to find the room has changed in strange, impossible ways.
7. You give birth to a knot of blind snakes and mud, twisted in the shape of a child. Some black magic has swapped them for your true baby.
8. Born with no eyes, just a smooth skull. It sings haunting melodies in the night. Some nights, you hear a refrain singing back from somewhere far away.
9. Sickly and weak, with thin, papery skin. There's a hive of wasps inside its brain. Sometimes they come out, through it's nose and ears, to gather small trinkets and return with them.
10. During the birth, three ragged elves arrive with long knives, planning to kill it. They don't speak your language.
11. During the birth, three richly-dressed elves arrive with gifts: A strange drug, a knife, and a knot of silk in a noose. They don't speak your language.
12. It bonds to you and grows, fungus-like.
13. Your significant other made some bad deals. An old man with two iron stakes stuck in his eyes arrives for the child. If you refuse to let him, he'll remove the stakes, ripping off his old man skin to become a raging wildfire that will swiftly consume everything around it. If your baby is set alight, it will instantly burn to become a perfect sculpture of ash, and the fire will abate.
14. It does nothing but scream constantly as the most wretched fluids of the earth pour from its every orifice, just like every baby.
15. The baby never stops bleeding, but has no wounds. You slowly grow weak from blood loss. 
16. Twins. One is disemboweled, with her organs wrapped around her sibling. Before they can be disentangled, the organs constrict and draw the still-mewling twin inside the open torso of the dead baby. As her chest seals over the living baby, her eyes open. She is bloated, but alive.
17. You are unable to feel anything but blinding, irrational hatred for it. If left alone with it for a long period, you'll need to save to avoid doing something terrible. 
18. Over the course of a night you give birth to 2d20 babies and a few gallons of tar.
19. It can't stop shaking. The shakes intensify until it's as if it's being thrown around the room by an invisible force.
20. Baby? You've never had a baby. What are you talking about?