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Leading Specialists in United States
Reproductive specialists in United States
Guy Ringler MD, FACOG
Reproductive Endocrinologist
Dr. Guy Ringler is a reproductive endocrinologist at Pinnacle Fertility Los Angeles (formerly California Fertility Partners), where he has practiced since moving to the city in 1990 to work with its founding physicians. He is known for surrogacy and third-party reproduction, helping LGBTQ+ individuals build families through egg donation and surrogacy. Patients travel from Europe, Asia, Australia, and Africa for his care.
United States 
Hakan Cakmak, MD
Reproductive Endocrinologist
Hakan Cakmak runs IVF and IUI cycles at UCSF with a research program aimed at two stubborn failures: embryos that do not implant and pregnancies that do not continue. He operates laparoscopically and hysteroscopically on the endometriosis, fibroids and uterine cavity problems behind them, and sees patients in English and Turkish.
United States 
Dr. Ilene Hatch
Reproductive Endocrinology and Infertility Specialist
Dr. Ilene Hatch is a double board-certified reproductive endocrinology and infertility (REI) specialist at Fertility Center of Southern California in Irvine, CA. With over 20 years of clinical experience, she serves as an assistant clinical professor at UC Irvine and brings personal understanding to patient care through her own fertility journey.
United States 
Dr. Heather Cook
Reproductive Endocrinologist
UCLA-trained reproductive endocrinologist at Coastal Fertility Specialists working on embryo assessment, egg donation and recurrent pregnancy loss.
United States 
Heather Huddleston, MD
Reproductive Endocrinologist
Heather Huddleston directs the UCSF PCOS Clinic and its research program — a named leadership role few centers have — and runs studies on recurrent pregnancy loss and uterine factor infertility. Harvard-trained, she diagnoses and treats complex uterine causes of infertility, including Asherman's syndrome, with hysteroscopy.
United States 
Carlos Hernandez-Nieto, MD
Reproductive Endocrinologist
Dr. Hernandez-Nieto is a Reproductive Endocrinology and Infertility specialist and Associate Director of Clinical Research at RMA of New York. Board certified by the Mexican College of Obstetrics and Gynecology, his professional interests include assisted reproduction, fertility preservation, endometriosis, diminished ovarian reserve, preimplantation genetic testing, and reproductive genetics. He is bilingual in English and Spanish.
United States 
Hooman Sadri, MD, PhD
Andrologist, Male Reproductive Medicine
Dr. Hooman Sadri is the andrologist on Carolinas Fertility Institute's roster: an MD, PhD who directs the male fertility research program at Wake Forest, serves as MD director on the American Society of Andrology board, and works in surgical sperm retrieval, vasectomy reversal, electro-ejaculation, Klinefelter syndrome and infertility after spinal cord injury.
United States 
James Smith, MD, MS
Reproductive Urologist
James Smith directs the UCSF Male Reproductive Health Center, the part of the Center for Reproductive Health that treats the male half of a couple's diagnosis. He runs the men's fertility preservation program, performs sperm retrieval, microsurgical vasectomy reversal and varicocele repair, and studies male reproductive biology.
United States 
Dr. Jamie Merkison
Reproductive Endocrinologist
Dr. Jamie Merkison is a reproductive endocrinologist at Reproductive Biology Associates (RBA), joining in September 2025 after completing her REI fellowship at Emory University. She began seeing new patients in October at RBA's Sandy Springs office. She earned her B.S. and M.D. from Howard University through an accelerated six-year program, graduating summa cum laude, and completed her residency at Baylor College of Medicine. Her clinical interests include fertility preservation, PCOS, diminished ovarian reserve and recurrent pregnancy loss.
United States 
Jenna Friedenthal, MD
Reproductive Endocrinologist
Dr. Jenna Friedenthal is a board-certified reproductive endocrinologist at RMA of New York and an assistant clinical professor at the Icahn School of Medicine at Mount Sinai. She specializes in fertility preservation (egg and embryo freezing), IVF with preimplantation genetic testing (PGT), and LGBTQIA+ family building. Her landmark study of early human embryonic mosaicism earned ASRM's highest awards.
United States 
Jennifer Agard, M.D.
Reproductive Endocrinologist
Jennifer Agard, MD is a double board-certified reproductive endocrinologist who serves Pacific Fertility Center's Marin County campus in Greenbrae, the North Bay alternative to driving into San Francisco. She trained at the Jones Institute — where IVF pioneer Howard Jones was her mentor — after UCLA medical school and residency at Saint Barnabas Medical Center, returned to the Bay Area in 2012, and has been named a Castle Connolly Top Doctor from 2020 through 2025.
United States 
Dr. Jennifer Dundee
Reproductive Endocrinologist
Board-certified reproductive endocrinologist, former USC clinical embryologist, and IVF director at the University of Vermont before joining Coastal Fertility.
United States Showing 157-167 of 612
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