OBJECTIVE: To evaluate peripheral joint laxity during pregnancy and to correlate changes with serum cortisol, estradiol, progesterone, and relaxin. METHODS: Forty-six women with first-trimester singleton gestations consented to participate in this longitudinal observational study. Bilateral wrist laxity measurements (flexion-extension and medial-lateral deviation) were made using a clinical goniometer, and serum levels of cortisol, estradiol, progesterone, and relaxin were determined during each trimester of pregnancy and postpartum. Patients were also screened for subjective joint complaints. Statistical analysis included Student t test, analysis of variance, and linear regression analysis. RESULTS: Eleven women (24%) were excluded from the study after spontaneous first-trimester pregnancy loss. Fifty-four percent (19 of 35) demonstrated increased laxity (10% or higher) in either wrist from the first to the third trimester. Although serum levels of cortisol, estradiol, progesterone, and relaxin were significantly elevated during pregnancy, no significant differences in these levels were noted between those who became lax during gestation and those who did not. Linear regression analysis of wrist joint laxity and level of serum estradiol, progesterone, and relaxin demonstrated no significant correlation. Wrist flexion-extension laxity, however, did significantly correlate with level of maternal cortisol (r = 0.18, P = .03). Fifty-seven percent of women developed subjective joint pain during pregnancy, which was not associated with increased joint laxity, but was associated with significantly increased levels of estradiol and progesterone. CONCLUSION: Peripheral joint laxity increases during pregnancy; however, these changes do not correlate well with maternal estradiol, progesterone, or relaxin levels.