By the Incinta Editorial Team · Medically reviewed by the Incinta Review Team
Losing one pregnancy is sadly common; losing two or more in a row can make every next step feel heavy with fear. If that is where you are, two things deserve to be said at the start: recurrent pregnancy loss is almost never your fault—it is not caused by anything you did, stressed over, or forgot to do—and it is one of the most actively investigated, genuinely treatable areas of fertility medicine. Many people who lose two or more pregnancies go on to deliver healthy babies, often without a single cause ever being found, and a structured evaluation uncovers treatable reasons in a meaningful share of cases. This guide explains what recurrent pregnancy loss is, how common it really is, the five major cause categories, what testing actually involves, which treatments have solid evidence (and which do not), and how to move forward—for patients here in Torrance and the South Bay.
1. What Is Recurrent Pregnancy Loss—and When Does It Warrant a Workup?
A miscarriage is the unexpected loss of a pregnancy before 20 weeks, per the National Library of Medicine (MedlinePlus); the National Institute of Child Health and Human Development (NICHD) also uses the broader term pregnancy loss. Recurrent pregnancy loss (RPL) is generally defined as two or more clinical pregnancy losses—pregnancies documented by ultrasound or by tissue examination—a definition used in guidance from the American Society for Reproductive Medicine (ASRM) and in patient guidance from the American College of Obstetricians and Gynecologists (ACOG).
Two clarifications keep the definition honest. First, clinicians distinguish clinical losses from biochemical losses—a positive test that fades before anything is visible on ultrasound; the latter are common and are usually counted separately, though a pattern of them is still worth mentioning to your physician. Second, the old teaching was to wait until three losses before investigating; practice has shifted, and most fertility physicians now start a workup after two losses—particularly when the female partner is 35 or older, when a loss was in the second trimester, or when the pattern feels like more than chance. Waiting for a third loss to “qualify” for testing is a rule whose time has passed.
2. How Common Is It—and the Number That Matters Most
Start with the baseline: per ACOG, roughly 10–20% of known pregnancies end in miscarriage, and most happen very early—frequently before a person even knows they are pregnant. Recurrent loss is far less common: figures commonly cited in ASRM and European (ESHRE) guidelines place it at about 1% of couples trying to conceive when defined as two or more consecutive clinical losses. So if you are living this, know that it is genuinely uncommon territory—and yet, paradoxically, the outlook is far better than most people assume.
Here is the single most important statistic in this entire guide. Even when no cause is found at all, commonly cited published figures put the chance of the next pregnancy succeeding at roughly 65–75% after two losses, and at about half or more after three losses—without any treatment beyond supportive care (figures of this magnitude appear in ACOG and ASRM materials drawn from large follow-up studies). The biology behind this is simple: most losses happen by chance—bad luck in the chromosome lottery of egg division—and chance does not compound the way fear tells you it does. These are population-level ranges, not a prediction for any individual, and they shift with age and with how many losses have occurred. But the direction of the truth is unmistakable: recurrent miscarriage is a grim-feeling diagnosis with a genuinely hopeful prognosis.
3. Cause One: Embryo Chromosomes—The Most Common Reason
When tissue from an early miscarriage is examined, commonly cited estimates attribute roughly half of first-trimester losses to chromosome errors in the embryo—an extra or missing chromosome (called aneuploidy) that stops development shortly after it starts. This is overwhelmingly a random event: it happens in the division of a single egg or sperm cell, it is not inherited in the usual sense, and it is not caused by lifting something, working hard, or having coffee.
The rate is strongly tied to the age of the egg. Published population estimates suggest a modest share of embryos is aneuploid in the mid-twenties, rising steeply through the thirties and to a large majority by the mid-forties—which is exactly why miscarriage risk climbs with age (Section 9). One useful pattern: first-trimester losses are usually chromosomal, while second-trimester losses more often point to anatomy, infection, or other causes—which is why the timing of a loss steers the workup. Two practical notes follow from this section. First, one miscarriage—even a second—usually reflects chance, not a broken system. Second, because embryo chromosome errors dominate, tools that inspect embryo chromosomes—such as the preimplantation genetic testing (PGT) used in IVF—enter the RPL conversation naturally, with honest caveats covered in Section 12. Where your ovarian reserve stands shapes which tools make sense for you, which is why it belongs in the evaluation.
4. Cause Two: A Parent’s Chromosome Rearrangement
In roughly 2–5% of couples with recurrent loss (a range commonly cited in the published literature), one partner carries a balanced structural chromosome rearrangement—most often a translocation, where two chromosome pieces have swapped places. The carrier is completely healthy: nothing is missing or extra, just rearranged. The problem appears at conception, when eggs or sperm can end up with an unbalanced amount of chromosome material—enough to stop development and cause a loss, often repeatedly.
This is why a karyotype—a simple blood test that maps both partners’ chromosomes—is a standard part of the RPL workup (Section 11). If a rearrangement is found, the news lands hard but comes with real options: genetic counseling to explain the specific pattern; IVF with PGT-SR, which identifies which embryos inherited a balanced or normal chromosome set so those are prioritized for transfer; or simply trying again, because many carriers produce some normal or balanced embryos and do conceive on their own—the odds per attempt are simply lower. ACOG’s patient FAQ on repeated miscarriages covers this exact scenario in plain language. The point worth holding onto: among all RPL causes, this is one where testing changes the plan immediately and concretely.
5. Cause Three: The Shape of the Uterus
The uterus is the embryo’s first home, and structural problems inside it are found in a meaningful share of RPL evaluations—commonly cited figures put a major uterine anomaly in roughly 10–15% of women with recurrent loss. The lineup:
- Septate uterus—the most common congenital anomaly associated with loss. A band of tissue (a septum) divides the uterine cavity down the middle; it has a poor blood supply, and embryos that implant on it often fail. It is present from birth, invisible from outside, and found only by imaging.
- Fibroids—muscle growths of the uterine wall. Only certain types matter here: those that bulge into or significantly distort the cavity (submucosal) are associated with implantation failure and loss.
- Polyps—overgrowths of the lining that can act like an IUD, interfering with implantation.
- Intrauterine adhesions (Asherman syndrome)—scar bands, most often after a D&C procedure, that can shrink the cavity.
- Cervical insufficiency—painless opening of the cervix, typically producing second-trimester losses; treated in a subsequent pregnancy with a stitch (cerclage).
Testing is straightforward imaging: a saline-infusion ultrasound (fluid outlines the cavity), an HSG X-ray study—our tubal-factor guide explains what that test involves—and, when findings need clarification, hysteroscopy, which both confirms and treats in one procedure (septum resection, polyp removal, adhesion release). An honest note on evidence: resecting a septum or removing a cavity-distorting fibroid is standard, widely practiced care, but much of the supporting evidence is observational rather than trial-based—a fair point to discuss with your physician when weighing surgery.
6. Cause Four: Hormonal and Medical Conditions
Several common medical conditions raise miscarriage risk or complicate early pregnancy—and all are manageable:
- Thyroid disease: an overtly underactive thyroid is clearly associated with miscarriage, and treating it is standard. Whether borderline thyroid function or thyroid antibodies alone increase risk is genuinely debated in the literature—a physician treats what is clearly abnormal and monitors what is not.
- Uncontrolled diabetes: poorly controlled blood sugar around conception sharply raises loss and birth-defect risk; well-controlled diabetes does not behave this way. Control before pregnancy is the intervention.
- Elevated prolactin: a pituitary hormone that, when too high, disrupts ovulation and the corpus luteum; it responds well to medication.
- PCOS: polycystic ovary syndrome brings anovulation and metabolic features, and published studies show somewhat higher early-loss rates—partly through embryo factors, partly through the metabolic environment. Our PCOS and fertility guide covers the condition in depth, including why the outlook with treatment is encouraging.
- Endometriosis: the inflammatory environment it creates is associated with both infertility and somewhat elevated loss rates in published research—our endometriosis guide explains the mechanisms and the treatment ladder.
The theme across this list: these conditions matter for the health of the next pregnancy regardless of whether they are the specific cause of past losses, so finding and treating them is worthwhile on multiple grounds. The evaluation includes simple bloodwork—TSH, prolactin, glucose or A1c—which is why the workup is mostly quick outpatient testing rather than an ordeal.
7. Cause Five: Antiphospholipid Syndrome—the Cause With a Proven Treatment
Every RPL guide should single out antiphospholipid syndrome (APS), because it is the classic example of a cause you can find and treat with demonstrated benefit. APS is an autoimmune condition in which the immune system produces antibodies that promote blood clotting in the small vessels of the placenta, choking off the embryo’s supply—typically causing early losses and sometimes second-trimester losses or growth problems. Depending on the population and criteria used, published figures commonly place APS in roughly 5–20% of women with recurrent loss.
Diagnosis is a blood panel—lupus anticoagulant, anticardiolipin antibodies, and anti-beta2-glycoprotein-I antibodies—that must be positive on two separate occasions at least 12 weeks apart, because antibodies can transiently rise after illness. That waiting requirement frustrates patients, and it exists for good reason: treatment is not trivial, so the diagnosis must be real.
Treatment, however, is remarkably simple: low-dose aspirin plus preventive-dose heparin injections during pregnancy. This combination is supported by randomized trial evidence and ACOG guidance, and it meaningfully improves the chance of a live birth in women with APS and recurrent loss. Heparin does not cross the placenta, so it is considered safe for the baby—one of the long-answered questions patients rightly ask. The broader lesson of this section: the RPL workup is not academic curiosity—it exists to find the subset of causes, like APS, where doing something specific changes the outcome.
8. The Honest Gray Zone: What Testing Cannot Prove Yet
A trustworthy guide has to name the places where evidence runs out, because recurrent loss attracts more unproven treatment than almost any other fertility topic. The main gray zones:
- Inherited clotting tendencies (thrombophilias) such as Factor V Leiden: associated with some late losses in published studies, but testing and blood-thinner treatment are not routinely recommended for early recurrent loss, because trials have not shown benefit—per ACOG and ASRM guidance.
- Immune-based testing and treatment—natural killer (NK) cell panels, intravenous immunoglobulin (IVIG), lymphocyte immunotherapy, TNF-blocker protocols: these remain investigational for RPL. Professional guidance from ASRM and ESHRE does not recommend them for routine use, because controlled studies have not shown reliable benefit, while the cost and burden are real. Be cautious with any clinic that hands every patient an “immune protocol” without a specific diagnosis.
- Sperm DNA fragmentation: an active research area with some published associations with loss, but no standard, proven treatment—a conversation worth having, framed honestly.
- Progesterone supplementation: intuitive and widely used, but a large UK randomized trial (PROMISE) and a 2020 Cochrane review found no significant overall benefit for unexplained recurrent loss; subgroup analyses have kept the question open, so some physicians use it selectively. It is not harmful in typical use—it is simply not the guaranteed answer it is often assumed to be.
None of this means the gray zone is empty of hope—it means the honest plan is to test for what is known, treat what is found, and lean on the strong natural prognosis for everything else, rather than spending months and money on protocols the evidence does not support. A clinic that says “this part is not proven” is protecting you, not rationing care.
9. Age, Egg Quality, and Ovarian Reserve
Age runs through this entire guide because it powers the most common cause: as eggs age, chromosome-division errors accumulate. Commonly cited population figures show miscarriage risk in the low teens percent range through the twenties and early thirties, rising to roughly one in four pregnancies by the late thirties, and to about half or more by the mid-forties (figures of this pattern appear in ASRM and ACOG materials). These are population averages—individual variation is real—but the trend line is one of the most reliable in medicine.
Two clarifications prevent common misunderstandings. First, ovarian reserve testing is not a miscarriage test. AMH and antral follicle count estimate how many eggs remain and how the ovaries will respond to treatment—our AMH and ovarian reserve guide explains what these numbers do and do not predict—but a strong AMH does not protect against age-related chromosome errors, and a low AMH does not by itself cause miscarriage. Second, age-related risk does not make older patients untreatable; it makes time the resource to manage. If pregnancy is not on the table yet, preserving younger eggs by freezing them is a real strategy worth discussing early—with the honest boundary that frozen eggs are planning, not a guarantee, since future odds depend on age at freezing and the number stored.
10. Lifestyle Factors—and Why Blame Is Almost Always Wrong
Almost every patient who has had a miscarriage privately replays their life looking for the mistake. So the frame matters: the large majority of losses are not preventable, and no activity, meal, workout, or stressful week causes a chromosomally abnormal embryo. That said, several lifestyle factors show genuine published associations with miscarriage risk, and optimizing them improves overall pregnancy health:
- Smoking: consistently associated with higher miscarriage risk in published research; quitting is one of the few true levers, and it matters for both partners.
- Alcohol: ACOG advises no alcohol during pregnancy—there is no established safe amount—and stopping as soon as pregnancy is possible is the practical guidance.
- Caffeine: commonly limited to about 200 mg per day (roughly one 12-oz cup of coffee) during pregnancy, per ACOG patient guidance.
- Body weight: obesity is associated with elevated loss risk in published studies; even modest, sustainable changes improve metabolic and pregnancy health. This is optimization, never punishment.
- Environmental exposures: high-dose radiation and certain industrial chemicals are the real-world concerns; everyday phones, laptops, and air travel are not.
One more honest note: the egg gets most of the attention, but sperm contributes half the embryo, and paternal factors—age, smoking, sperm DNA quality—belong in the picture too. That is one more reason a partner’s semen analysis is part of every complete RPL evaluation, not an optional extra.
11. The RPL Evaluation: What Testing Actually Involves
The workup sounds intimidating and mostly is not. It is a bounded checklist—blood draws, imaging, and one optional procedure—usually completed within a few weeks:
- Karyotype for both partners—the blood test from Section 4 that finds a rearrangement in roughly 2–5% of couples.
- Antiphospholipid antibody panel—the Section 7 tests, repeated 12 weeks apart if positive.
- Uterine imaging—saline-infusion ultrasound, an HSG, or hysteroscopy when needed, to find septums, fibroids, polyps, and adhesions (Section 5).
- Hormone and metabolic labs—TSH, prolactin, glucose or A1c—plus ovarian reserve testing (AMH, antral follicle count) to inform planning.
- Semen analysis for the male partner—quick, inexpensive, and plan-changing, as our male infertility and ICSI guide explains.
When to start: per the definitions in Section 1, after two clinical losses—and earlier if you are 35 or older or had a second-trimester loss. Two outcome notes deserve equal billing with the tests. First, even after everything above, roughly half of RPL cases remain “unexplained”—and as Section 2 showed, unexplained is the category with the best natural prognosis of all. Second, a complete evaluation includes both partners by design, so the search never spends months optimizing the wrong person’s variables. The evaluation’s purpose is not to assign blame—it is to catch the treatable minority and give every couple the clearest possible starting line.
12. Treatment Paths: What Has Evidence, What Is Individualized
Treatment after RPL is genuinely individualized—but the map of what is proven is clear:
- Treat what the workup found: hysteroscopic surgery for a septum, cavity-distorting fibroids, or adhesions; aspirin plus heparin for APS; medication for overt thyroid disease or elevated prolactin; glucose control before conception for diabetes. Each of these follows directly from a specific finding—which is exactly why the evaluation comes first.
- IVF with PGT for chromosome problems: for a parent with a balanced rearrangement, IVF with PGT-SR has a clear rationale—it identifies balanced embryos for transfer. For unexplained RPL, IVF with PGT-A (aneuploidy screening) is more nuanced: it can reduce miscarriage risk by not transferring clearly aneuploid embryos, particularly at older ages, but it does not create better embryos or raise the total chance of live birth from a given batch of embryos, and professional guidance favors individualized counseling rather than routine use. Our PGT guide and complete IVF guide for Torrance cover the mechanics; national expectations by age are published by CDC ART surveillance—population ranges, not predictions.
- Trying again with structured support: for unexplained RPL, simply trying again—with early-pregnancy ultrasounds and attentive follow-up—is an evidence-based plan, not a shrug, because of the strong natural success rates in Section 2. Published cohorts of RPL patients given structured supportive care show success rates comparable to treated groups in several studies.
- What IUI is and is not here: insemination does not treat recurrent loss—the loss mechanism sits in the embryo, the uterus, or the immune/clotting system, not in how sperm arrives. IUI appears in RPL planning only when a separate infertility factor exists; our IUI vs. IVF comparison explains how those decisions are made.
Notice the pattern: the interventions with the strongest evidence are the ones matched to a found cause, and the honest default for everyone else is time plus support—with IVF and PGT added where age, embryo count, or a genetic finding makes them genuinely useful rather than reflexively.
13. The Emotional Weight—and Practical Ways Through
Recurrent loss is a medical topic that is also a grief topic, and pretending otherwise would make this guide useless. The published literature is clear that repeated loss is associated with anxiety, depression, and strain on relationships—and that partners often grieve differently from each other, which adds a second layer of misunderstanding at exactly the moment couples need each other most. None of this is weakness; it is the normal human response to repeated, private loss.
What measurably helps, per the research and per clinical practice: counseling or a support group with people who understand this specific experience; involving your partner in appointments so information does not have to be relayed; and planning the next pregnancy differently—many programs offer early ultrasounds and check-ins in pregnancies after loss, not because risk demands them in every case, but because reassurance has real value for parents who have earned their vigilance. Ask directly what follow-up in a next pregnancy would look like; a good clinic has an answer ready. And when the evaluation or treatment path needs to move forward, the team approach matters—mental health, medical workup, and family-building planning belong in one conversation, not three separate sagas.
14. Taking the Next Step
Recurrent pregnancy loss has a way of making people feel like their body has failed a test they never knew they were taking. The evidence says something different: two losses in a row usually mean chance, not brokenness; the workup is a short, bounded checklist that finds a treatable cause in a meaningful minority of cases; and for everyone else, the prognosis—roughly two-thirds success in the next pregnancy without any intervention—remains one of the best in all of fertility medicine. The sequence is short: evaluation after two losses, both partners included; treat the treatable; add IVF with genetic testing where age or a specific finding justifies it; and move forward with support rather than in the dark. If you are ready for that evaluation, the path starts with a conversation and a handful of outpatient tests—not with another month of anxious waiting.
15. Frequently Asked Questions
How many miscarriages should I have before getting tested?
Current practice starts the workup after two clinical pregnancy losses, per ASRM and ACOG guidance—and sooner if you are 35 or older or had a second-trimester loss. The old “wait for three” rule has largely been retired.
What are my chances of a successful pregnancy after recurrent miscarriage?
Commonly cited published figures put the next pregnancy’s success at roughly 65–75% after two losses and about half or more after three—even without treatment. A found-and-treated cause (such as APS or a uterine septum) can improve on that, and age adjusts it. Population ranges, not predictions for any individual.
What tests are done for recurrent pregnancy loss?
A karyotype for both partners, antiphospholipid antibody testing, uterine evaluation (saline ultrasound, HSG, or hysteroscopy), thyroid/prolactin and metabolic labs, ovarian reserve testing, and a semen analysis. Most is bloodwork plus imaging, completed within a few weeks.
Can IVF with genetic testing prevent miscarriage?
It depends on the cause. For a parent with a balanced chromosome rearrangement, IVF with PGT-SR has a clear role in identifying balanced embryos. For unexplained loss, PGT-A can reduce miscarriage risk by avoiding clearly aneuploid embryos—especially at older ages—but it does not improve the embryos themselves or guarantee a live birth, so guidance favors individualized counseling.
Is progesterone recommended after recurrent miscarriage?
Not routinely for unexplained loss: a large randomized trial (PROMISE) and a 2020 Cochrane review found no significant overall benefit. Some physicians use it selectively in specific situations—it is not harmful in typical use, but it is not the guaranteed answer it is often assumed to be. Whether it fits your case is a physician decision.
Ready to replace uncertainty with a plan? Schedule a consultation with our fertility specialists in Torrance for a complete recurrent-loss evaluation—both partners, all major causes—and a clear, compassionate path to your next pregnancy.
Incinta Fertility Center — Fertility Clinic Torrance & South Bay, California. Patient-first care, bilingual support, and laboratory leadership you can trust.
