A reproductive endocrinologist (RE) is a physician who specializes in diagnosing and treating complex reproductive disorders, including infertility, hormonal imbalances, and structural problems affecting the reproductive system. These doctors complete roughly 12 years of training after college: four years of medical school, four years of OB/GYN residency, and an additional three years of fellowship focused specifically on reproductive endocrinology and infertility (REI). That extra training is what separates them from a general OB/GYN and qualifies them to perform advanced procedures like IVF.
What REs Do Beyond Basic Fertility Care
Your OB/GYN can handle initial fertility evaluations, track ovulation, and prescribe basic fertility medications. A reproductive endocrinologist picks up where that generalist care ends. REs are trained to investigate the deeper hormonal, genetic, anatomical, and molecular causes of reproductive problems. They manage conditions that involve the complex interplay between the reproductive system and other body systems, including bone health, cancer-related fertility concerns, and congenital abnormalities of the reproductive tract.
In practical terms, this means an RE is the specialist who performs IVF, manages ovarian stimulation with injectable medications, interprets complex hormone panels, and conducts advanced reproductive surgeries using minimally invasive techniques designed to preserve fertility. They also have extensive training in genetic screening of embryos, carrier testing before pregnancy, and the use of donor eggs, donor sperm, and gestational carriers.
Training and Certification
After completing medical school and a full OB/GYN residency, a reproductive endocrinologist spends three additional years in a fellowship accredited by the Accreditation Council for Graduate Medical Education (ACGME). Some programs offer a four-year track that includes genetics training. During fellowship, they gain deep expertise in reproductive hormone action at the tissue and cellular level, learn advanced surgical techniques, and complete an original research thesis that must be defended before a committee.
Board certification comes through the American Board of Obstetrics and Gynecology (ABOG). Candidates must first pass the general OB/GYN qualifying exam, then complete at least 32 of 36 fellowship months before sitting for the subspecialty exam. They also need an unrestricted medical license by the time they take the certifying portion.
Conditions REs Diagnose and Treat
Infertility is the most common reason people see a reproductive endocrinologist, but these specialists treat a wide range of conditions:
- Polycystic ovary syndrome (PCOS), one of the most common causes of irregular ovulation
- Endometriosis, where tissue similar to the uterine lining grows outside the uterus
- Premature ovarian insufficiency, sometimes called premature menopause
- Recurrent miscarriage, typically defined as two or more pregnancy losses
- Uterine fibroids and structural abnormalities of the reproductive tract
- Menstrual irregularities, including absent periods
- Excess hair growth and other signs of hormonal imbalance
- Puberty disorders
REs also handle male factor infertility, which contributes to roughly half of all infertility cases. They order and interpret semen analyses, check hormone levels like testosterone and FSH, and coordinate with reproductive urologists when a man needs specialized treatment for low sperm production or structural issues.
What Happens at Your First Visit
A fertility workup with an RE typically involves several diagnostic tests. For women, this often includes blood work to check hormone levels related to ovulation and ovarian reserve (how many eggs remain and their likely quality). The blood test is paired with a pelvic ultrasound to count the small follicles visible on each ovary. Together, these give the RE a picture of your remaining fertility window.
To check whether the fallopian tubes are open, your RE may order a hysterosalpingography (HSG), which uses X-ray and a special dye to create an image of the uterus and tubes. A saline sonogram works similarly, using sterile saltwater and ultrasound to look for polyps, fibroids, or other structural issues inside the uterus. For the male partner, at least one semen analysis is standard, and guidelines recommend two samples collected at least a month apart since sperm counts can vary significantly between ejaculations.
Procedures and Treatments
Reproductive endocrinologists are experts in all agents used to stimulate ovulation, from oral medications to injectable hormones. When those approaches are paired with intrauterine insemination (IUI), where prepared sperm is placed directly into the uterus, it represents a less intensive treatment step before IVF.
IVF is the most well-known procedure REs perform. It involves stimulating the ovaries to produce multiple eggs, retrieving those eggs, fertilizing them in a lab, and transferring a resulting embryo to the uterus. Within that process, REs can offer preimplantation genetic testing (PGT) to screen embryos for chromosome abnormalities or specific inherited conditions before transfer. They also perform egg freezing and embryo freezing for people who want to preserve their fertility for the future, whether for medical reasons like cancer treatment or personal timing.
On the surgical side, REs specialize in minimally invasive procedures to remove fibroids, treat endometriosis, or correct structural problems in the uterus and fallopian tubes, all with an emphasis on protecting or improving fertility.
Family Building for All Paths to Parenthood
Reproductive endocrinologists coordinate third-party reproduction services for anyone who needs them. This includes donor sperm, donor eggs, and gestational surrogacy. LGBTQ+ individuals and couples, single parents by choice, and people with medical conditions that prevent them from carrying a pregnancy all use these services. Major academic fertility centers like UCSF specifically offer comprehensive family-building programs that include IUI with donor sperm, IVF with donor eggs, and gestational carrier arrangements.
When to See a Reproductive Endocrinologist
Clinical guidelines define infertility as failure to conceive after 12 months of unprotected intercourse for women under 35, or after 6 months for women 35 and older. For women over 40, more immediate evaluation is recommended. Up to 15% of couples experience infertility by these definitions. You don’t necessarily need a referral from your OB/GYN to book an appointment, though some insurance plans require one.
Age isn’t the only reason to seek earlier evaluation. If you have known risk factors like irregular or absent periods, a history of pelvic surgery, endometriosis, PCOS, or a partner with known fertility concerns, seeing an RE sooner rather than later gives you more options and more time to act on them.