What is a fertility doctor called? Comparing REIs, OB-GYNs, and PCPs

Temeka Zore, MD, FACOG - Contributor Avatar

Reviewed by Temeka Zore, MD, FACOG, 

Written by Rachel Sanoff 

Temeka Zore, MD, FACOG - Contributor Avatar

Reviewed by Temeka Zore, MD, FACOG, 

Written by Rachel Sanoff 

last updated: May 11, 2021

9 min read

Navigating the healthcare system while seeking out fertility treatment isn’t easy. When you do a simple Google search to get some advice, it's like there's a new language with jumbles of letters you might not recognize. What's the difference between an OB-GYN, REI, and a PCP? And who do you go to for fertility issues and potential treatments? Acronyms can be pretty central to conversations about pregnancy and fertility, so it’s helpful to have a glossary in mind while searching for the right doctor to support you.

Modern Fertility is here with the answers you need as you take charge of your reproductive health, wherever you are on your fertility journey:

  • What’s a PCP, and when should you see one? A primary care physician (PCP) is your go-to for non-emergency healthcare.

  • What does an OB-GYN do, and when should you see one? An obstetrician-gynecologist (OB-GYN) covers your reproductive lifespan (from first period through menopause) and provides care for patients through pregnancy.

  • What does an REI do, and when should you see one? A reproductive endocrinologist who specializes in infertility (REI) diagnoses and treats infertility and recurrent miscarriage.

Read on to get more in-depth answers, learn the differences between the doctor types, and pick up a handy list of questions to ask yourself so you know who to turn to and when.

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What’s a PCP?

"PCP" can be used interchangeably to refer to either your primary care physician or primary care provider — aka the healthcare practitioner you visit for common, non-emergency needs and annual checkups. PCPs are typically practitioners who are dedicated to general healthcare (an internist, family physician, nurse practitioner, or a physician's assistant), but other specialists (like an OB-GYN, which we'll discuss in the next section) may also cover your primary care.

Here's the training and education you need to become a board-certified PCP:

  • A PCP needs a bachelor’s degree and four years of medical school to receive an MD or DO.

  • They must complete three or more years in a postgraduate residency program with a specific area of focus, such as family medicine, internal medicine, or pediatrics.

  • To become board-certified, the doctor must pass exams from their governing medical body after graduation from an accredited residency program.

When's it time to see a PCP?

Anytime you need non-emergency, general healthcare and for your annual checkups. If your needs are outside your PCP's expertise, they'll refer you to a specialist — though some family physicians also work with pregnant patients and deliver infants. If you have an OB-GYN who's taking care of your general healthcare needs (which many do) and you don't have any chronic issues that fall under a different specialty, you don't necessarily need a PCP.

What’s an OB-GYN?

An OB-GYN is a doctor who specializes in female reproductive health, or obstetrics and gynecology (OB-GYN stands for obstetrician-gynecologist). Your OB-GYN provides healthcare for you from the time you enter puberty until menopause, otherwise known as your entire reproductive lifespan — as well as during pregnancy and through birth.

While OB-GYN refers to one specialty, doctors may exclusively practice obstetrics or gynecology. Obstetrics refers to preconception pregnancy care, as well as birth and delivery. Gynecology is a broader field encompassing all of women's health. Not all gynecologists are also obstetricians (meaning not all gynecologists will deliver infants).

Here's the training and education you need to become a board-certified OB-GYN:

  • An OB-GYN needs a bachelor’s degree, followed by four years of medical school where they’ll receive an MD or DO.

  • They must complete a minimum of four years in an accredited OB-GYN residency program where they’ll do rotations on obstetrics, gynecology, gynecological oncology, high-risk obstetrics, urogynecology, ultrasounds, and reproductive endocrinology (we’ll dive deeper into this last subject in the next section).

  • To become board-certified, the doctor must pass exams through the American Board of Obstetrics and Gynecology after graduation from an accredited residency program.

When's it time to see an OB-GYN?

You should visit an OB-GYN when you’re seeking healthcare that specifically relates to your reproductive organs, whether or not you’re trying to get pregnant:

1. All throughout your reproductive years: The first recommended time to see an OB-GYN is after your first period, which is typically between ages 13 and 15. Throughout your life as a menstruating person, you can visit an OB-GYN for treatment and guidance regarding:

2. If you need general reproductive and/or sexual healthcare: General reproductive healthcare and sexual healthcare include:

3. If you need certain surgeries and procedures: OB-GYNs also perform surgeries and procedures affecting the female reproductive organs, including:

  • Hysterectomy (removal of the uterus)

  • Colposcopy (cervical biopsy)

  • Tubal ligation

  • Myomectomy (removal of uterine fibroids)

  • Dilation and curettage (removal of excess tissue from the uterus, also known as D&C)

  • Endometrial and uterine biopsies

  • Intrauterine insemination (IUI), which can also be performed by REIs (more on REIs later)

4. If you need preventative care: In addition to any appointments with your OB-GYN for specific gynecological or obstetric care, you’ll see them for your annual visit (sometimes called a wellness exam). During a general or annual appointment, you’ll receive (based on age-recommended guidelines):

  • General health screening

  • Cervical cancer screenings (your Pap smear)

  • Breast cancer screenings

  • STI testing

5. If you need preconception care: An OB-GYN is often considered your “first stop” on a fertility journey because they provide preliminary care. You’ll first see an OB-GYN for a preconception appointment where you’ll discuss your goal of conceiving and how best to make that happen. And while your OB-GYN can detect out-of-range hormone levels (aka hormonal "imbalance") through blood work, they'll refer you to a fertility specialist for more complex fertility issues. We’ll talk about fertility specialists in a bit.

6. During pregnancy and delivery: If your gynecologist isn't also an obstetrician, they can recommend you to someone who is so you'll have support throughout pregnancy and birth:

  • Once you’re pregnant (or think you may be pregnant), an OB-GYN can test for pregnancy via blood work and an ultrasound.

  • During pregnancy, your OB-GYN will provide prenatal care and manage any issues for you and/or your fetus.

  • If your OB-GYN has admitting privileges at the hospital you want to deliver at, they'll deliver your infant.

  • Your OB-GYN will also provide care to you after birth.

Midwives can also provide much of the above services and often consult with OB-GYNs or other healthcare professionals if more medical support is needed.

The differences between PCPs and OB-GYNs

There's sometimes overlap in what PCPs and OB-GYNs cover care-wise:

  • Your OB-GYN may provide gynecological care and primary care (like blood pressure checks and cholesterol screenings).

  • Your PCP may also provide gynecological exams and work solely with patients who have vaginas or are pregnant.

  • If your OB-GYN provides primary care but you regularly have healthcare needs that are beyond the scope of an OB-GYN, you may need the additional support of a PCP or other specialist.

What’s an REI?

REI stands for reproductive endocrinology and infertility, which is the same acronym used for doctors who practice this specialty: reproductive endocrinologists. There's no difference between a reproductive endocrinologist and a fertility specialist. REIs specialize in providing assisted reproductive technologies (ART), managing complex reproductive endocrine (read: hormonal) conditions, and treating issues related to female fertility. (While REIs also work with opposite-sex couples dealing with "male factor" infertility, reproductive urologists specialize in the area.)

Here's the training and education you need to become a board-certified REI:

  • An REI initially receives the same education as an OB-GYN: a bachelor’s degree, four years of medical school, and a minimum of four years in an accredited OB-GYN residency program with rotations in different specialty areas.

  • Since reproductive endocrinology and infertility is a boarded subspecialty of obstetrics and gynecology, aspiring REIs must also complete a three-year fellowship in addition to their four-year residency program. In these fellowships, they’ll study complexities of the human reproductive system and specific treatments and procedures.

  • To become board-certified, the doctor must pass exams in both obstetrics and gynecology and reproductive endocrinology and infertility through the American Board of Obstetrics and Gynecology.

When's it time to see an REI?

An OB-GYN or PCP will usually refer you to an REI if you’ve encountered fertility problems while trying to conceive (TTC). Typically, this will happen after six months of TTC without getting pregnant if you’re older than 35 and 12 months of TTC if you’re younger than 35. But you might talk to an REI about treatment options on your own if you already know you’ll need access to the healthcare they provide (before waiting 6-12 months):

1. If you're interested in fertility treatments and ART: Before developing a treatment plan, your REI will likely ask you to undergo blood panels and ultrasounds so they can understand any underlying causes of infertility (like an undiagnosed health condition, out-of-range hormone levels, structural issues in the uterus or fallopian tubes). Based on the results of this fertility testing, your REI may recommend various fertility treatments (like oral or injectable ovulation-inducing medications) or go straight to ART (procedures like in-vitro fertilization, intracytoplasmic sperm injection, and IUI).

2. If you're curious about fertility preservation: Your REI may also talk to you about fertility preservation by way of egg freezing. This procedure helps extend your potential reproductive timeline by retrieving your younger, healthier eggs, flash-freezing them, and storing them in a laboratory for later use. Your REI might recommend egg freezing if fertility tests reveal you have a diminished ovarian reserve, if you will soon undergo cancer treatment that will impact your ovaries, or if you plan on trying to conceive in the far-off future.

3. If you're having trouble getting pregnant: In addition to being able to diagnose and treat you for a specific fertility issue, an REI can help you navigate unexplained infertility or consider next steps after three or more ovulation-induction treatment cycles without success. REIs also work with patients (in conjunction with reproductive urologists) to help treat male infertility. REIs provide semen analysis (aka sperm tests) to help them measure the health of a patient’s sperm and whether it can successfully make the journey to fertilize an egg. Based on their findings, an REI may recommend one of the previously mentioned ART methods or suggest using a sperm donor.

4. If you've experienced recurrent pregnancy loss: If you’ve experienced two or more miscarriages on your fertility journey, known as recurrent miscarriage, a fertility specialist can help figure out the cause of pregnancy loss and work with you to potentially conceive through ART.

The difference between OB-GYNs and REIs

What are the most important differences between OB-GYNs and REIs, and what doctor do you see for fertility?:

  • An OB-GYN provides care throughout your entire reproductive lifespan, while an REI provides care when you’re trying to conceive. But once you’ve conceived, you’re back at an OB-GYN’s office for help managing a healthy pregnancy and to eventually deliver your newborn.

  • An OB-GYN will diagnose and treat specific issues that relate to reproductive health, including PCOS, endometriosis, fibroids, and thyroid conditions. But once you’re TTC and those same conditions may complicate the process, an REI will work with you to manage your symptoms, treat infertility, and help you get pregnant.

Ultimately, fertility specialists and OB-GYNs are separated by different training, education backgrounds, services provided, and in the case of REIs, expertise in both male and female reproductive systems.

Summing it all up: How do all of these doctors compare?

Now that we've talked about each of these types of providers individually and compared certain practices, let's drive home the main points about all three:




Their training:

- Bachelor’s degrees

and medical degrees.

- Three or more years


an accreditedpostgraduate residencyprogram

 with a specific

area of focus.

- Board-certified by

completing exams through

their governing medical

body (family medicine,

internal medicine).

What they do:

- Provide healthcare for

common, non-emergency

medical needs.

Their training:

- Bachelor’s degrees

and medical degrees.

- At least four years


an accredited OB-GYNresidency program


- Board-certified by

passing exams through

the American Board of

Obstetrics and Gynecology.

What they do:

- Cover the reproductive

lifespan (from first

period through menopause)

and care for patients

through pregnancy.

Their training:

- Bachelor’s degrees

and medical degrees.

- At least four years


an accredited OB-GYNresidency program


A three-year fellowship


- Board-certified by

passing exams through

the American Board of

Obstetrics and Gynecology.

What they do:

- Specialize in

reproductive endocrinology,

infertility, and

miscarriage diagnosis and


How do you know if you need to go to a fertility specialist instead of an OB-GYN?

You can figure out which direction to go on your fertility journey by asking yourself these questions:

  • Have you tried to conceive for six months and you’re older than 35? You’re ready to visit an REI at a fertility clinic.

  • Have you tried to conceive for one year and you’re younger than 35? You’re ready to visit an REI.

  • Regardless of how long you’ve tried to conceive, do you already know that you have a health condition that affects your hormones or reproductive organs? You can visit an REI now (or whenever you’re comfortable).

  • Does your partner with sperm already know about a health condition that affects their hormones or reproductive organs? Same answer! No need to wait — head over to an REI when you’re comfortable.

  • Is there a chance that you may want to conceive in the future, but definitely not yet? Talk to an REI about proactively planning for your family now with fertility preservation.

If you do decide to go to an REI, Dr. Temeka Zore, MD, FACOG, a Modern Fertility medical advisor and an REI, explains that you can expect the following:

  • A detailed review of you and your partner's full medical and reproductive history

  • A basic infertility workup

  • A transvaginal ultrasound to look at your uterus, ovaries, and follicle count

In addition, Dr. Zore says your REI will provide an overview of the causes of infertility and may also cover fertility treatment options and their success rates.

Modern Fertility is here to help you figure out the right path for you

We know that finding the right doctor for such important and personal healthcare may feel like a daunting task. Our goal is to make reproductive health as easy to understand as possible.

Whether it’s through articles, virtual events, at-home tests, or our free Modern Community, we want you to have the care, support, and fact-based info you deserve.

This article was reviewed by Dr. Temeka Zore, a Modern Fertility medical advisor and reproductive endocrinologist at Spring Fertility in San Francisco.


If you have any medical questions or concerns, please talk to your healthcare provider. The articles on Health Guide are underpinned by peer-reviewed research and information drawn from medical societies and governmental agencies. However, they are not a substitute for professional medical advice, diagnosis, or treatment.

How we reviewed this article

Every article on Health Guide goes through rigorous fact-checking by our team of medical reviewers. Our reviewers are trained medical professionals who ensure each article contains the most up-to-date information, and that medical details have been correctly interpreted by the writer.

Current version

May 11, 2021

Written by

Rachel Sanoff

Fact checked by

Temeka Zore, MD, FACOG

About the medical reviewer