The reproductive endocrinology and infertility subspecialist: definition, training, and scope of practice in the United States
Download a PDF of this document
Reproductive endocrinology and infertility (REI) subspecialists are physicians with extensive and specialized training in the diagnosis and treatment of complex reproductive disorders. This unique expertise allows them to provide the highest level of care for patients requiring advanced services for family building, reproductive surgery, and endocrine disorders affecting the female reproductive system. Expertise in reproductive medicine relies on applied physiology and revolves around a fundamental understanding of endocrine physiology and reproductive hormone action at the tissue, cellular, and molecular levels. In addition, an REI’s understanding of the fundamentals of study design and data analysis is essential to understand medical literature, adapt to the rapidly changing medical literature, and promote better individualization of care. Reproductive endocrinology and infertility subspecialists are trained surgeons of the female reproductive tract who particularly specialize in minimally invasive surgical approaches, with an emphasis on minimal tissue trauma. REI physicians are trained in the diagnosis and treatment of endocrine, genetic, anatomical, structural, and molecular causes of reproductive disorders, including infertility and advanced fertility options, such as assisted reproductive technologies. This document discusses the training and role of the reproductive endocrinology infertility subspecialist in the United States. (Fertil Steril ® 2025;124:1201–9. ©2025 by American Society for Reproductive Medicine.)
In the United States, reproductive endocrinology and infertility (REI) subspecialists must complete medical school, an Accreditation Council for Graduate Medical Education (ACGME) accredited 4-year Obstetrics and Gynecology residency, and an ACGME-accredited REI fellowship program (1,2). Reproductive endocrinology and infertility fellowship programs are 3 years in length, during which the fellow receives specialized training in the diagnosis and treatment of reproductive disorders. Fellowship training consists of at least 18 months of clinical rotations, 12 months of research to ormulate and complete an adequate thesis, and 6 months of elective rotations (3). Training includes requirements for performing specialized surgical and procedural cases, including hysteroscopy, laparoscopy, transvaginal ultrasounds, oocyte retrieval, and embryo transfer. As of 2024, there are 52 active REI fellowship programs training, which can graduate 68 REI physicians annually, with programs participating in the Electronic Residency Application Service match (4). All REI fellowship programs in the United States are accredited by the ACGME (5). The board certification process for REI subspecialists is most commonly under the American Board of Obstetrics and Gynecology and less commonly under the American Osteopathic Board of Obstetrics and Gynecology. Board-certified REIs have completed rigorous training in reproductive and gynecologic medicine and surgery and meet the highest certification for treating the depth and breadth of reproductive medicine.
The practice of ART is regulated by several governing bodies, including the US Food and Drug Administration, Clinical Laboratory Improvement Amendments, College of American Pathologists, Joint Commission, and Centers for Disease Control & Prevention. Per guidance from the Society for Assisted Reproductive Technology (SART) and the American Society for Reproductive Medicine, only an American Board of Obstetrics and Gynecology or American Osteopathic Board of Obstetrics and Gynecology board-certified (or an active candidate for board certification) REI physician can serve as the Medical Director of each ART program. Reproductive endocrinology and infertility physicians with appropriate training and skills can also be certified as High Complexity Laboratory Directors and run the ART laboratory itself. As Medical Director of an ART program, the REI physician leads the multidisciplinary team, including embryologists, nurses, andrologists, urologists, anesthesiologists, geneticists, mental health providers, and others. The REI physician as Medical Director is ultimately responsible for running the ART program and remaining current with updated data entry reporting requirements to report their program’s complete and accurate data to SART and the Centers for Disease Control & Prevention. Reproductive endocrinology and infertility physicians have the training necessary to oversee the multidisciplinary ART program, ranging from third-party reproduction, US Food and Drug Administration requirements, legal issues, and potential risks to offspring, and to maintain a structured program for monitoring quality assurance and improvement. In addition to approving annual program SART data, the SART Medical Director's responsibilities include creating, reviewing, and updating facility policies and procedures, ensuring appropriate modality education and selection for all patients, providing supervision of medical personnel, and ensuring safe and effective patient care. SART Medical Directors must practice ART at the SART member clinic.
COMPLEX REPRODUCTIVE ENDOCRINOLOGY
Reproductive endocrinology and infertility subspecialists are experts in the physiology, pathology, diagnosis, and treatment of complex endocrine disorders related to the reproductive system. This includes knowledge of hypothalamic, pituitary, adrenal, and gonadal hormone action. Extensive knowledge and clinical skills are needed to treat diseases ranging from primary and secondary amenorrhea to endometriosis and uterine fibroids. Reproductive endocrinology and infertility subspecialists are trained to manage complex diseases that extend beyond treating infertility associated with endocrine disease and include the complex interplay of the reproductive system with bone, cancer, anatomical, and other disease processes. These treatments often include the management of hypoestrogenism and menstrual suppression.TRANSVAGINAL ULTRASONOGRAPHY
Reproductive endocrinology and infertility subspecialists have extensive training in performing and interpreting transvaginal ultrasounds, typically logging hundreds to thousands of transvaginal ultrasound procedures during fellowship. Reproductive endocrinology and infertility physicians are fully trained in performing, supervising, and interpreting transvaginal ultrasound for gynecology and early obstetrics, and no further certification is required (6).DIAGNOSTICS AND THERAPEUTICS
Reproductive endocrinology and infertility physicians are experts in the selection and interpretation of diagnostic tests for reproductive disorders, including infertility, endometriosis, and polycystic ovary syndrome (Table 1). The REI subspecialist understands the pathophysiology of reproductive diseases, molecular biology techniques, clinical research methodology, and critical evaluation of literature. Therefore, the REI subspecialist is the most appropriate physician for selecting, interpreting, and managing diagnostics and therapeutics in reproductive endocrinology and infertility. Given their expertise, REI subspecialists are integral to advancing the field of REI through research.ADVANCED OVULATION INDUCTION AND OVARIAN STIMULATION
Reproductive endocrinology and infertility physicians are experts in the management of all agents utilized to induce ovulation or conduct ovarian stimulation. Adverse outcomes associated with ovarian stimulation include multiple gestation, ovarian hyperstimulation syndrome (OHSS), and other rare but serious complications, such as cyst rupture and ovarian torsion. Reproductive endocrinology and infertility physicians mitigate the risks of adverse events associated with ovulation induction and ovarian stimulation utilizing transvaginal ultrasound, hormone assay assessment, and other information. Reproductive endocrinology and infertility physicians monitor for ovulation timing via transvaginal ultrasound and hormonal assays. Reproductive endocrinology and infertility physicians receive training to safely and effectively manage ovarian stimulation with gonadotropins, which are the most likely medications to cause adverse events related to multiple gestation and OHSS. Although obstetricians and gynecologists and other clinicians may receive some training in performing intrauterine inseminations, REI is the only specialty dedicated to hands-on training in cases of difficult entry into the uterus, such as challenging intrauterine insemination, saline sonogram, and embryo transfer procedures. Reproductive endocrinology and infertility physicians have an overarching understanding of the relevant medical literature, not only the clinical components but also the laboratory components of fertility treatments and their role in developing an appropriate treatment strategy for a particular patient.ADVANCED REPRODUCTIVE SURGERY
Reproductive endocrinology and infertility physicians are experts in performing advanced reproductive and gynecologic surgery in patients who wish to optimize their fertility. Reproductive endocrinology and infertility physicians are specifically trained to focus on minimizing tissue trauma and enhancing the function of reproductive structures, particularly the endometrium, ovary, fallopian tubes, and uterus. Surgical outcome data consistently demonstrate that surgical volume is key to good surgical outcomes (7). Advanced reproductive surgery, such as for severe endometriosis, complex ovarian cystectomy, reconstructive procedures, tubal surgeries, myomectomy, rare M€ ulleriananomalies, hysteroscopic treatment of uterine synechia, and uterine transplantation, should be managed or comanaged by an REI or, if not available, specialists or subspecialist surgeons who have acquired additional training, experience, and skills to perform such surgeries in a fashion that optimizes reproductive outcomes. Fertility-preserving surgeries, such as ovarian and uterine transposition, ovarian tissue harvest, cryopreservation, and reimplantation, typically involve REI physicians who have the expertise and tools to offer a wide range of fertility preservation options.Reproductive genetics
Reproductive endocrinology and infertility physicians have extensive training in prepregnancy genetic carrier screening and the use of genetic testing of embryos for aneuploidy, monogenic disease, and translocations. Reproductive endocrinology and infertility physicians must understand the mechanisms, benefits, and limitations of genetic testing platforms, such as next-generation sequencing, polymerase chain reaction, and single-nucleotide polymorphism, and be able to counsel patients on the clinical utility of these tests. Reproductive endocrinology and infertility subspecialists are trained in the diagnosis of female reproductive genetics and disease and their reproductive management. Reproductive endocrinology and infertility subspecialists are trained in the diagnosis and management of genetic diseases that have reproductive phenotypes, such as genetic causes of primary ovarian insufficiency, abnormal puberty, and disorders of sexual development. Management of reproductive genetic pathology often involves a complex team of medical professionals, with the interface of that management being the REI physician.ASSISTED REPRODUCTIVE TECHNOLOGIES
Assisted reproductive technology (ART) involves various procedures used to help patients achieve pregnancy via the removal of sperm and oocytes from the body to create embryos. Reproductive endocrinology and infertility physicians have a comprehensive understanding of the medical and laboratory components of the ART procedures and extensive experience developing treatment plans to maximize success and mitigate risk in ART. Reproductive endocrinology and infertility subspecialists are the only physicians formally trained to perform oocyte retrievals and embryo transfers. As with all surgeries and procedures, adequate surgeon procedural volume is necessary to optimize patient outcomes. Reproductive endocrinology and infertility fellows receive extensive training in ART procedures to become proficient in their utilization. In addition to the procedures themselves, REI physicians use ovarian stimulation to maximize oocyte yield and minimize OHSS. Reproductive endocrinology and infertility physicians are trained experts in the complexities of third-party reproduction, including oversight over the medical, legal, and social aspects of counseling and developing the best treatment strategy.The practice of ART is regulated by several governing bodies, including the US Food and Drug Administration, Clinical Laboratory Improvement Amendments, College of American Pathologists, Joint Commission, and Centers for Disease Control & Prevention. Per guidance from the Society for Assisted Reproductive Technology (SART) and the American Society for Reproductive Medicine, only an American Board of Obstetrics and Gynecology or American Osteopathic Board of Obstetrics and Gynecology board-certified (or an active candidate for board certification) REI physician can serve as the Medical Director of each ART program. Reproductive endocrinology and infertility physicians with appropriate training and skills can also be certified as High Complexity Laboratory Directors and run the ART laboratory itself. As Medical Director of an ART program, the REI physician leads the multidisciplinary team, including embryologists, nurses, andrologists, urologists, anesthesiologists, geneticists, mental health providers, and others. The REI physician as Medical Director is ultimately responsible for running the ART program and remaining current with updated data entry reporting requirements to report their program’s complete and accurate data to SART and the Centers for Disease Control & Prevention. Reproductive endocrinology and infertility physicians have the training necessary to oversee the multidisciplinary ART program, ranging from third-party reproduction, US Food and Drug Administration requirements, legal issues, and potential risks to offspring, and to maintain a structured program for monitoring quality assurance and improvement. In addition to approving annual program SART data, the SART Medical Director's responsibilities include creating, reviewing, and updating facility policies and procedures, ensuring appropriate modality education and selection for all patients, providing supervision of medical personnel, and ensuring safe and effective patient care. SART Medical Directors must practice ART at the SART member clinic.
Table 1: Summary of the training standards and skillset of REI physicians (derived from published ACGME milestones and ABOG bulletin for subspecialty certification) (2,6)
| Topic area | Topic subheadings | Examples (not definitive lists) |
| Basic science, physiology, and pathophysiology |
|
|
| Diagnostic techniques and interpretation for the management of reproductive disorders |
|
|
| Evaluation, diagnosis, and management of reproductive endocrine function and disease |
|
|
| Female fertility, female infertility, and PCOS |
|
|
| Male infertility |
|
|
| Recurrent pregnancy loss |
|
(e.g., contribution of endocrine factors, immunologic factors, anatomic factors, and genetic factors, and relative incidence of each) and counsel patients regarding prognosis and causes of RPL |
| Fertility preservation |
|
|
| Assisted reproductive technology (ART) techniques |
|
Embryo grading systems (e.g., ASRM/SART and Gardner), normal and abnormal embryo development, laboratory conditions (e.g., media, buffers for pH stability and temperature), understanding laboratory key performance indicators (KPIs), and how to troubleshoot laboratory problems |
| Evaluation, diagnosis, and management of complex reproductive disorders |
|
|
| Complex reproductive and surgical procedures |
|
|
| Genetics |
|
|
| ABOG = American Board of Obstetrics and Gynecology; ACGME = Accreditation Council for Graduate Medical Education; ACTH = adrenocorticotropic hormone; ASRM = American Society for Reproductive Medicine; CAP = College of American Pathologists; CDC = Centers for Disease Control & Prevention; CLIA = Clinical Laboratory Improvement Amendments; FDA = US Food and Drug Administration; GnRH = gonadotropin-releasing hormone; HSG = hysterosalpingography; MRI = magnetic resonance imaging; NGS = next-generation sequencing; PCR = polymerase chain reaction; SART = Society for Assisted Reproductive Technology; SIS = saline infusion sonohysterography; SNP = single-nucleotide polymorphism. Practice Committee of the Society for Reproductive Endocrinology and Infertility and Practice Committee of the American Society for Reproductive Medicine. The reproductive endocrinology and infertility subspecialist. Fertil Steril 2025. | ||
Research and evidence-based medicine
Reproductive endocrinology and infertility physicians complete 12 months of required training in medical research, with an optional 6 additional elective months of research. Reproductive endocrinology and infertility physicians are examined on research methods, including statistical analysis, and are required to submit a research thesis as part of their board certification. Training in and performing research are vital to the continued advancement of the areas of REI medicine, including but not limited to the rapid evolution of the field of ART. The REI’s practice of evidence-based medicine is enhanced by the robust research training received during the fellowship. Even for REI physicians no longer actively involved in research, the extensive research training allows REI physicians to critically appraise the literature on rapidly changing innovation that occurs in reproductive medicine.Fertility preservation
Reproductive endocrinology and infertility physicians are experts in the complexities of managing fertility preservation for both medical indications and future family planning. Medical indications include gonadotoxic therapies for diseases, such as cancer treatment with chemotherapy, pelvic abdominal radiation, or diseases requiring gonadotoxic treatment. Reproductive endocrinology and infertility physicians are trained to counsel patients with BRCA mutations regarding family planning and genetic testing of embryos. Reproductive endocrinology and infertility physicians provide counseling and treatment for fertility preservation for transgender patients undergoing gonadal suppression or gonadectomy. Some diseases are associated with primary ovarian insufficiency, such as mosaic Turner Syndrome, and require expert counseling and management on the optimal timing, as well as limitations of fertility preservation options in this group. Reproductive endocrinology and infertility physicians are trained in counseling for family planning and fertility preservation for the age-related decline in fertility. Although these are just some examples of fertility preservation counseling and treatment that REIs perform, REIs are trained to provide the complex counseling needed for each unique patient scenario.CONCLUSION
Reproductive endocrinology and infertility subspecialist physicians are experts on the diagnosis and management of complex reproductive and gynecologic disorders. To assure both continued access to high-quality care for reproductive disorders and advancement in the field, REI fellows should continue to receive extensive training across the breadth and depth of the subspecialty, including reproductive physiology, endocrine disorders, minimally invasive surgery, critical evaluation of the literature to interrogate emerging technologies and therapeutics, and training in the counseling and management of infertile patients, as well as those seeking fertility treatment for other indications. Reproductive care, especially when requiring advanced therapeutics and surgery, complex endocrinology, and reproductive genetics, should require management with or the direct oversight of an REI subspecialist.Acknowledgments
This report was developed under the direction of the Practice Committees of the American Society for Reproductive Medicine (ASRM) and the Society for Reproductive Endocrinology and Infertility (SREI) as a service to its members and other practicing clinicians. Although this document reflects appropriate management of a problem encountered in the practice of reproductive medicine, it is not intended to be the only approved standard of practice or to dictate an exclusive course of treatment. Other plans of management may be appropriate, taking into account the needs of the individual patient, available resources, and institutional or clinical practice limitations. The Practice Committee and the Board of Directors of the American Society for Reproductive Medicine have approved this report.This document was reviewed by ASRM members, and their input was considered in the preparation of the final document. The following members of the ASRM Practice Committee participated in the development of this document: Clarisa Gracia, M.D., M.S.C.E.; Paula Amato, M.D.; Jacob Anderson; Rebecca Flyckt, M.D.; Karl Hansen, M.D., Ph.D.; Micah Hill, D.O.; Tarun Jain, M.D.; Sangita Jindal, Ph.D.; Suleena Kalra, M.D., M.S.C.E.; Bruce Pier, M.D.; Denny Sakkas, Ph.D.; Anne Steiner, M.D., M.P.H.; Cigdem Tanrikut, M.D.; Belinda Yauger, M.D.; Robert Brannigan, M.D.; Elizabeth Ginsburg, M.D.; Jared Robins, M.D.; Chevis N Shannon, Dr.Ph., M.B.A., M.P.H.; and Madeline Brooks, M.B.A., M.P.H. The Practice Committee acknowledges the special contributions of Jennifer Eaton, M.D., Chantel Cross, M.D., and Seif Sadek, M.D., in the preparation of this document. All Committee members disclosed commercial and financial relationships with manufacturers or distributors of goods or services used to treat patients. Members of the Committee who were found to have conflicts of interest on the basis of the relationships disclosed did not participate in the discussion or development of the document.
References
- Reproductive endocrinology and infertility qualifying exam. Available at: https://www.abog.org/subspecialty-certification/reproductive-endocrinologyand-infertility/qualifying-exam. Accessed May 5, 2023.
- Reproductive endocrinology and infertility certifying exam. Available at: https://www.abog.org/subspecialty-certification/reproductive-endocrinology-and-infertility/certifying-exam. Accessed May 5, 2023.
- Subspecialty case list thesis, case list, and abbreviations. Available at: https:// www.abog.org/subspecialty-certification/thesis-guidelines#Content_C011_ Col00. Accessed May 5, 2023.
- ERAS 2023 participating specialties & programs. Available at: https://systems. aamc.org/eras/erasstats/par/display.cfm?NAV_ROW=PAR&SPEC_CD=235. Accessed May 5, 2023.
- Committee R. Case log Instructions: reproductive endocrinology and infertility. Available at: https://www.acgme.org/globalassets/pfassets/programresources/ rei_case_log_instructions.pdf. Accessed May 5, 2023.
- Practice Committee of the American Society for Reproductive Medicine. American Society for Reproductive Medicine position statement on qualifications for providing ultrasound procedures in reproductive medicine. Fertil Steril 2022;118:668–70.
- Morche J, Mathes T, Pieper D. Relationship between surgeon volume and outcomes: a systematic review of systematic reviews. Syst Rev 2016;5: 204.
Practice Documents
ASRM Practice Documents have been developed to assist physicians with clinical decisions regarding the care of their patients.
Fertility preservation in patients with medical indications: a committee opinion (2026)
Expert guidelines on fertility preservation options—oocyte, embryo, ovarian and testicular tissue cryopreservation and counseling before gonadotoxic treatment.
The reproductive endocrinology and infertility subspecialist: definition, training, and scope of practice in the United States (2025)
Reproductive endocrinology and infertility (REI) subspecialists are physicians with extensive and specialized training in the diagnosis and treatment of complex reproductive disorders.
Improving access to care and delivery to marginalized and vulnerable populations: a committee opinion (2025)
ASRM committee opinion on reducing infertility care disparities, outlining barriers and actionable strategies to improve equitable access.
Gamete and embryo donation guidance (2024)
Explore the latest guidelines for evaluating sperm, oocyte, and embryo donors and recipients. Includes FDA, CDC, and ASRM standards for optimal safety and outcomes.Topic Resources
View more on the topic of infertility