Using a pulse oximeter, the investigators have developed an algorithm that assesses central volume status. Pregnant women present some unique opportunities for us to investigate the algorithm under different circumstances. The investigators want to specifically investigate an algorithm with women who undergo regional anesthesia such as epidurals, with women who undergo fetal surgery, and with women in labor and giving birth (and the recovery time following delivery). This will help the investigators understand the central volume status changes that women experience in these unique circumstances. The Investigators also want to put the pulse oximeter on the fetal hand when possible during certain maternal fetal interventions. The Investigators would like to examine the algorithm with data from the fetuses.