Family trait analysis: a case-control study of 43 women with endometriosis and their best friends.

Analyses of lineage patterns show that for 43 women with endometriosis who reported that other family members have the disease, the vast majority of these familial cases involve the maternal lineage (79% to 93%). Of these women 34.9% of their mothers and 21.2% of their sisters were affected. With use of these rates, expected rates for first-degree relatives in a general population of women with endometriosis were determined. These rates were 6.2% and 3.8%, respectively; in combination, these rates yield an overall risk of 4.9% for first-degree relatives. Prior studies estimated this overall risk to be 6.9%; however, z scores determined that these rates do not differ statistically. Rates for second-degree maternal relatives are reported for grandmothers and aunts (0.4% compared to 3.1%, respectively), thus expanding results of former studies. In combination, an overall risk of 1.9% is estimated for second-degree relatives, as measured.