Vomiting before labor

I know this sounds crazy but I have a severe phobia of throwing up and I keep reading that in the hours before labor many women throw up a lot. I got lucky and had no puking from my morning sickness or at all during pregnancy. I'm 34 weeks so I'm starting to get nervous about throwing up before labor. Have any moms skipped this labor symptom? And if not how long does the throwing up usually last?