I’m going to start off with the disclaimer that I don’t believe in superstitions. I DO find them interesting however.

Like, if your baby does the downward dog pose, it means he’s “looking for a sibling” (aka you’ll get pregnant soon). I just thought it was cute he was doing a yoga pose. The question is, how many siblings is he looking for??
Another one I heard was that if you have a lot of heartburn, your baby will have a full head of hair. I got asked that a lot since my baby had a full head of hair when he came out – most people’s first comments are “Look at that hair!”. But no, I didn’t have heartburn during pregnancy.
I was also told (before we found the gender) that the more nausea I had, the more likely it was to be a boy. Since I didn’t really get morning sickness (and off topic, why do they call it that?? It doesn’t necessarily happen only in the morning!), my mom thought I’d have a girl. Again, I had a boy. However, my cousin-in-law had HORRIBLE morning sickness and is having a boy.
The last one I recall, though not really a superstition as much as a saying, is “If your baby looks like your husband, then you must love him a lot”. This one cracks me up. For those of you who haven’t walked back what it means if it doesn’t look like your partner, the implication is that the baby isn’t his! At least this one sort of makes sense to me!