Other than parity, and infant size, the etiology of the great variability in labor pain us unknown. Previous studies have demonstrated that baseline pain sensitivity is related to postoperative pain and narcotic requirement. We hypothesize that baseline pain sensitivity is related to pain in labor. We will determine baseline sensitivity to heat, cold and pressure as measurement of pain sensitivity. Furthermore, b2 adrenergic genotype has recently been identified as a potential determinant of pain sensitivity. We will determine whether B2 receptor haplotype is an independent predictor of pain experienced in labor.