An arcuate uterus is a minor variation in the shape of the uterus where the top of the cavity has a small, smooth inward dip rather than a flat or gently convex ceiling. It affects roughly 4% of women in the general population and sits at the mildest end of the spectrum of congenital uterine differences. Whether it should be considered an anomaly at all is genuinely debated among reproductive specialists, and that debate has real consequences for how it is managed during pregnancy and fertility treatment.
How Common It Is and What It Means for Fertility
A large systematic review pooling data across multiple studies found arcuate uterus in about 3.9% of unselected women. That makes it one of the most common uterine shape variations. The same review found something reassuring: the prevalence was not higher in women struggling with infertility (about 1.8%) or in women with a history of miscarriage (about 2.9%) compared with the general population.1PubMed Central. The prevalence of congenital uterine anomalies in unselected and high-risk populations: a systematic review In other words, having an arcuate uterus does not appear to make it harder to get pregnant, and it does not on its own predict recurrent pregnancy loss. This stands in contrast to the septate uterus, which the same review identified as the most common anomaly specifically in high-risk populations.
Because arcuate uterus is so common and doesn’t seem to cluster in women with fertility problems, many clinicians treat it as a normal variant rather than a true malformation. That framing matters: a diagnosis of “uterine anomaly” can cause significant anxiety, and for most women with this shape variant, that anxiety may be unwarranted.
The Classification Fight That Decides Whether It Exists
One of the most confusing things about an arcuate uterus is that whether you receive the diagnosis at all depends on which classification system your doctor uses. The two main systems used worldwide disagree on whether the arcuate uterus is even a real category.
The older American system (from the ASRM) lists arcuate uterus as its own class of uterine anomaly. In this framework, a small smooth fundal indentation gets labeled “arcuate,” and a deeper or more angular indentation gets called “septate.” The newer European system (ESHRE-ESGE) eliminated the arcuate category entirely. Under that system, what would have been called arcuate is either reclassified as a mild septate uterus or considered normal, depending on measurements of the uterine wall.2Fertility and Sterility. Reliability of the European Society of Human Reproduction and Embryology/European Society for Gynaecological Endoscopy and American Society for Reproductive Medicine classification systems for congenital uterine anomalies detected using three-dimensional ultrasonography
This is not just an academic turf war. A comparison study found that the European system diagnosed septate uterus at a significantly higher rate than the American system because it absorbed many former arcuate cases into the septate category. Among cases that the European system labeled septate, the internal fundal indentation was less than one centimeter in a substantial number, cases that the American system would have classified as normal.3Human Reproduction. Comparison of the ESHRE–ESGE and ASRM classifications of Müllerian duct anomalies in everyday practice In practical terms, a woman seen at one clinic might be told her uterus is normal or arcuate, while the same woman at another clinic might be told she has a septate uterus. The treatment implications of those two diagnoses are very different.
Reliability studies have also found that the arcuate uterus category is where observers disagree the most. When different clinicians looked at the same imaging, their biggest inconsistencies under the American system involved identifying arcuate uterus.4Fertility and Sterility. Reliability of the European Society of Human Reproduction and Embryology/European Society for Gynaecological Endoscopy and American Society for Reproductive Medicine classification systems for congenital uterine anomalies detected using three-dimensional ultrasonography The shape sits in a gray zone between clearly normal and clearly abnormal, which makes consistent diagnosis difficult regardless of which system is used.
How an Arcuate Uterus Gets Detected
Most women with an arcuate uterus discover it incidentally, during imaging for something else. A standard two-dimensional ultrasound can sometimes suggest an unusual uterine contour, but three-dimensional ultrasound is far more reliable for pinning down the specific shape.
One study found that 3D ultrasound achieved perfect diagnostic accuracy and sensitivity for detecting uterine anomalies in general, including arcuate, septate, and bicornuate types, when compared against the gold-standard combination of laparoscopy and hysteroscopy.5The Egyptian Journal of Radiology and Nuclear Medicine. Role of three-dimensional ultrasound in the diagnosis of double uterine cavity anomalies and concordance with laparoscopic and hysteroscopic diagnosis However, classifying the specific type of anomaly is trickier. Another study reported that 3D ultrasound accuracy for correctly classifying anomalies was about 76%, but when arcuate uteri and short septa were removed from the analysis, accuracy jumped to 95%.6PubMed. Accuracy of 3-dimensional sonography for diagnosis and classification of congenital uterine anomalies The arcuate shape is the one most likely to be miscategorized, which circles back to the classification problem: the boundary between arcuate and normal, or between arcuate and mildly septate, is inherently fuzzy.
MRI can also visualize the uterine shape in detail and is sometimes used when ultrasound is inconclusive or when other anomalies are suspected. But for most women, 3D ultrasound is the first and often only test needed.
Pregnancy Risks That Do Show Up
Even though an arcuate uterus does not appear to impair fertility, it is not entirely benign during pregnancy. The evidence consistently points to a few specific complications that occur at higher rates.
A systematic review and meta-analysis found that arcuate uterus was associated with a roughly two-and-a-half-fold increase in second-trimester miscarriage and a similar increase in fetal malpresentation at delivery.7PubMed. Reproductive outcomes in women with congenital uterine anomalies: a systematic review The malpresentation finding makes anatomical sense: even a mild indentation at the top of the uterine cavity can influence how a growing fetus settles in the available space, making breech or transverse positions more likely.
A large population-based cohort study of over 3.8 million women found additional risks. Women with an arcuate uterus had roughly two to three times the odds of preterm premature rupture of membranes (PPROM), nearly three times the odds of preterm delivery, and about twice the odds of placental abruption compared to matched controls.8PubMed Central. Pregnancy and neonatal outcomes in women with arcuate uterus: a population-based cohort study of over 3.8 million women These are relative risks, meaning they describe the increase compared to the baseline rate. The absolute risk of any individual pregnancy ending in one of these complications remains relatively low, because the baseline rates for preterm delivery and placental abruption are already low in the general population.
A study focused specifically on breech presentation in congenitally malformed uteri found that arcuate uterus was associated with worsened fetal and placental characteristics when breech deliveries were compared with matched controls. This finding was present across other types of uterine malformation too, but arcuate uterus showed a notable signal even though it is the mildest variant.9PubMed Central. Corrected evaluation of the breech presentation outcome based on etiology of this presentation in congenitally malformed uterus
The takeaway for someone with a known arcuate uterus who becomes pregnant: your pregnancy is not automatically high-risk, but your provider may want to pay closer attention to fetal positioning in the third trimester and monitor for signs of preterm labor. First-trimester miscarriage rates, which are the most common type of pregnancy loss overall, do not appear to be elevated.
What Happens with IVF
If you’re undergoing fertility treatment and learn you have an arcuate uterus, the evidence on whether it matters for IVF outcomes is genuinely split, and the disagreement seems to come down to how the embryos were selected.
A study that looked specifically at IVF cycles where embryos had been screened for chromosomal normality before transfer found no difference in outcomes between women with an arcuate uterus and those with a normal uterine cavity. Implantation rates (about 64% versus 65%), live birth rates (about 69% versus 68%), and miscarriage rates (about 5% versus 4%) were essentially the same. The authors concluded that arcuate uterus should be considered an incidental finding with no indication for surgical correction before IVF.10PubMed. Arcuate uterus: is there an impact on in vitro fertilization outcomes after euploid embryo transfer?
On the other hand, an earlier study that did not pre-screen embryos for chromosomal status found dramatically lower pregnancy and live birth rates in women with arcuate uterus compared to controls. When at least one top-quality embryo was transferred, pregnancy rates were about 21% in the arcuate group versus 36% in controls, and live birth rates dropped to just 3% versus 30%.11PubMed. Septate, subseptate and arcuate uterus decrease pregnancy and live birth rates in IVF/ICSI
How to reconcile these contradictory results? The most plausible explanation is that when embryos are chromosomally normal and implant successfully, the mild shape variation of an arcuate uterus does not prevent a healthy pregnancy. But when a mix of chromosomally normal and abnormal embryos are transferred, the slight anatomical difference may compound the already-lower odds of implantation for abnormal embryos, dragging down the overall success rates. The practical implication is that if you have an arcuate uterus and are pursuing IVF, genetic screening of embryos before transfer may effectively neutralize any impact the uterine shape has on your outcomes.
Surgery and Whether It Helps
Hysteroscopic metroplasty, a minimally invasive procedure where a small camera and instrument are inserted through the cervix to remove or reshape tissue at the top of the uterine cavity, is well-established for treating septate uterus. For arcuate uterus, the picture is much less clear.
Some clinicians have performed metroplasty on arcuate uteri, especially in women with recurrent pregnancy loss. One study found that after hysteroscopic metroplasty in women with recurrent miscarriage, the term delivery rate for those with an arcuate uterus was about 56%, compared with about 63% for those with a septum and 67% for those with a T-shaped uterus. The differences between groups were not statistically significant.12Gynecologic and Obstetric Investigation. Term Delivery Rate after Hysteroscopic Metroplasty in Patients with Recurrent Spontaneous Abortion and T-Shaped, Arcuate and Septate Uterus Another study found that women who conceived after metroplasty had lower miscarriage rates and higher delivery rates compared to their own previous pregnancies.13PubMed. Uterine anomalies and pregnancy outcome following resectoscope metroplasty
The problem with this evidence is that none of it comes from randomized controlled trials. Women who had surgery are being compared to their own prior outcomes, and pregnancy loss is common enough in the general population that subsequent pregnancies often succeed regardless of intervention. Without a proper comparison group of women with arcuate uterus who did not have surgery, it is impossible to say whether the improved outcomes reflect the surgery or just the natural probability of a better result next time.
A study looking at outcomes after hysteroscopic division of arcuate and incomplete septate anomalies in women with primary infertility found that clinical pregnancy rates (about 75%) and delivery rates (about 63–68%) were similar between the two groups after treatment.14PubMed Central. Reproductive outcome after IVF following hysteroscopic division of incomplete uterine septum/arcuate uterine anomaly in women with primary infertility These are encouraging numbers, but again, without a no-surgery control arm, it’s hard to know how much credit the procedure deserves.
Given the mild nature of the arcuate shape and the lack of strong evidence that surgery improves outcomes, most reproductive medicine guidelines do not recommend routine metroplasty for arcuate uterus. Surgery is generally reserved for cases where there is recurrent pregnancy loss and no other identifiable cause, or where the indentation is deep enough that the distinction from a true septum becomes academic.
Kidney and Other Associated Anomalies
Because the uterus and kidneys develop from neighboring tissue during fetal life, more severe uterine anomalies (like a unicornuate or didelphys uterus) are frequently accompanied by kidney abnormalities such as a missing kidney or a misplaced one. Naturally, women diagnosed with any uterine anomaly sometimes worry about whether they should be checked for kidney problems too.
For arcuate uterus, the concern is largely unfounded. A study that specifically examined renal tract malformations found that common minor uterine variants, including arcuate uterus, partial bicornuate, and partial septate, were rarely associated with kidney anomalies. Only about 3.8% of women with these minor variants had any renal tract abnormality at all.15Clin Obstet Gynecol Reprod Med. Renal tract malformations associated with Müllerian duct anomalies That rate is only marginally higher than what you’d expect in the general population. More severe uterine anomalies carry substantially higher rates of kidney involvement, but the arcuate uterus does not warrant routine kidney imaging on its own.
When You’re Told You Have One
If imaging reveals an arcuate uterus and you are not currently trying to become pregnant and have no symptoms, the finding typically requires no treatment, no follow-up testing, and no change in your healthcare. Many radiologists will mention it on an ultrasound report as a descriptive finding, the same way they might note a small ovarian cyst that will resolve on its own.
If you’re planning pregnancy or currently pregnant, the finding is worth mentioning to your OB-GYN but should not be a source of alarm. The associations with second-trimester loss, preterm delivery, and malpresentation are real but modest in absolute terms. Most women with an arcuate uterus carry pregnancies to term without complications. What the diagnosis does justify is attentive prenatal care, particularly monitoring fetal position in the third trimester and being aware that breech presentation may be more likely. A conversation with your provider about delivery planning is reasonable, but surgical correction before pregnancy is not standard practice.
The classification confusion can make this harder to navigate. If your report says “arcuate uterus” and a second opinion calls it a “mild septate uterus,” you are probably looking at the same anatomy described through different lenses rather than a genuine disagreement about what your uterus looks like. Asking your provider which classification system they used and what the actual measurements showed can help clarify the situation. The depth and angle of the indentation matter more than the label.
Why This Anomaly Resists a Clean Answer
Arcuate uterus occupies an awkward position in reproductive medicine. It is common enough that some experts argue it is simply a normal shape variant. The fact that one of the two major classification systems has abolished the category entirely supports this view. Yet the pregnancy outcome data, particularly on second-trimester loss and preterm delivery, suggests that even a mild fundal indentation can have clinical consequences in some pregnancies.
The underlying challenge is measurement. The transition from a flat uterine fundus to a shallow dip to a true septum is continuous, not stepped. Drawing a line and saying “above this threshold it’s normal, below it it’s an anomaly” will always be somewhat arbitrary. Different classification systems draw that line in different places, and individual observers don’t always agree even within the same system. Until there is consensus on where normal ends and arcuate begins, and ideally until randomized trials test whether surgery changes outcomes, the evidence will remain patchwork. For individual patients, the most honest clinical approach is to acknowledge the anatomy, monitor pregnancy closely, and resist the impulse to intervene surgically unless there is a compelling reason beyond the shape on the scan.