Do babies go into sleep mode before labor?

Hard to say: Babies "mode" during labor would be hard to study. Sleep states are generally documented by eeg study, which is impossible in labor.Labor itself can vary in length from a few hours to a day or more and i doubt baby would be aleart or asleep for it all. Moms note fetal movements between contractions at various stages of labor, but movement can occur in sleep. Just list this as an unknown.