I had observed that many lesbians I knew were physically somewhat masculine - thick waisted, strong featured. These can be symptoms of Polycystic Ovarian Syndrome, and there have been studies that lesbians do have a higher prevalance of this disorder, which causes insulin resistance and increased production of androgens.
Whether the androgens cause lesbian feelings, or whether the often cruel rejection by men of this body type causes a retreat to lesbianism, I don't know.
Mrs VS
As I pointed out in my Comment # 15, stress in pregnancy can cause hormonal changes that can affect a developing baby toward a more feminine or masculine tendency.