Risk factors for varicose disease before and during pregnancy have been analyzed by use of data from a survey on venous disease in pregnancy conducted in 611 women (mean age thirty years, range fifteen to forty-seven) who consecutively delivered at the Obstetric-Gynecologic Clinic "L. Mangiagalli" of Milan between January and April, 1989. In total, 137 women (22%) reported varicose disease before the index pregnancy. The relative risk (RR) of varicose disease before the index pregnancy increased with age, being, as compared with women aged twenty-nine years or less, 1.6 in those aged thirty to thirty-four and 4.1 in those aged thirty-five years or more (chi 2(1) trend 25.28, p < 0.001). Compared with nulliparae, women reporting a full-term pregnancy before the index pregnancy had an RR of venous disease of 1.2, and the risk increased to 3.8 in women reporting two or more births (chi 2(1) trend 25.28, p < 0.001). A family history of varicose disease was associated with an RR of venous disease of 6.2 (95% confidence interval, CI, from 4.1 to 9.6). No relationship emerged between varicose disease and overweight. Of the 474 women who did not report venous disease before the index pregnancy, 132 (28%) developed venous disease during the index pregnancy. The risk of developing venous disease in pregnancy increased with age, being, as compared with women aged twenty-four years or less, 4.0 in those aged thirty-five years or more, and the trend in risk was statistically significant (chi 2(1) trend 16.25, p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)