Let's be real for a minute — what's cooler than an ultrasound? Nothing. I looked forward to each and every one of mine with the enthusiasm of a kid headed to Disneyland. One day, my OB pointed out a fuzzy shadow, and said my baby had a full head of hair. While I dutifully reported this to my family, it really didn't look like hair to me, and sonography is echolocation — what bats and dolphins use to get around — not the camera of your iPhone 6. So can you actually see hair on the ultrasound, or was my OB just trying to make me feel better about the fuzzy blob on the screen?
Yes, an ultrasound paints your baby's picture in sound waves, but as it turns out, these machines are excellent these days (by week 32, you can see your baby's toenails, and by 39, eyelashes). According to Parents, ultrasounds are so sensitive that they absolutely show baby hair, waving gently in an amniotic bath, often early in the third trimester. One caveat: you're not exactly seeing the hair your baby will be born with, but a sort of pre-hair called lanugo, which keeps your baby warm while they develop some insulating body fat.
Today's Parent reported that babies usually lose their lanugo between weeks 32 and 36, and that premature babies might be born with their protective fur. In premature babies, lanugo eventually falls out and is replaced by vellus, the "peach fuzz" that grows on hairless areas of the body (feel your earlobe and see for yourself). If you do see hair in a late ultrasound, it will probably look like white strands on the scalp, or a fuzzy white halo.
Speaking of hair, you know that old wives' tale about pregnancy heartburn meaning hair? Turns out, it's true. I'm not even joking — Johns Hopkins studied it, and tastefully admitted their own surprise.
Even after your baby's birthday, you should know that you're probably not styling the final product with those pink barrettes. Terminal hair will grow in when your child's 2, and a lot changes from birth 'til then: color, texture, and thickness continue to evolve years after your baby's last in-utero photo shoot.