Complex sentence: He is principally known for his work in the field of donor oocyte and embryo transfer and achieved the world's first donor egg pregnancies in older menopausal women while serving as an Associate Professor at the University of Southern California in Los Angeles.
Split into simpler sentences: He is principally known for his work in the field of donor oocyte and embryo transfer. Sauer achieved the world's first donor egg pregnancies in older menopausal women while serving as an Associate Professor at the University of Southern California in Los Angeles.