Complex sentence: Lesbian women who were at the estrogen peak of their fertile cycle reported increased motivation for sexual contact with women, whereas bisexual women reported only a slight increase in same-sex motivated sexual contact during peak estrogen levels.
Split into simpler sentences: Lesbian women who were at the peak of their fertile cycle (associated with heightened levels of estrogen) reported increased motivation for sexual contact with women. Bisexual women reported only a slight increase in same-sex motivated sexual contact during peak estrogen levels.