Demographic Considerations in Diagnosing Interstitial Ectopic Pregnancy

A new retrospective study out of Boston Medical Center has shed light on a persistent diagnostic challenge in reproductive medicine: the misdiagnosis of interstitial ectopic pregnancy (IEP). Though rare, IEPs pose a serious clinical risk due to their propensity for delayed rupture and massive hemorrhage—yet nearly three-quarters of cases in this review were initially misdiagnosed.

Drawing on seven years of patient data, the study examined 53 women who presented between 2012 and 2019 with either suspected or confirmed interstitial ectopic pregnancy. Researchers compared those who received a correct diagnosis at initial presentation with those who did not, in an effort to identify patterns and risk factors behind diagnostic error.

The findings point to age as a key differentiator. Patients who were correctly diagnosed at first presentation were significantly older—averaging just over 35 years—compared to a mean age of 30.4 years in the misdiagnosed group. This age disparity held even when controlling for gravidity, suggesting that younger age itself may contribute to diagnostic oversight.

While factors like gravidity and parity showed some association with diagnostic accuracy in univariate analyses, these did not remain significant after adjusting for age. Other clinical factors—including BMI, smoking status, pelvic surgery history, reproductive tract anomalies, and prior pelvic infections—did not show any strong correlation with misdiagnosis.

The challenge of diagnosing IEP lies in its anatomical subtlety. Nestled in the proximal portion of the fallopian tube where it traverses the muscular uterine wall, an interstitial pregnancy can appear deceptively intrauterine on standard imaging. Delays in diagnosis increase the risk of catastrophic bleeding, often requiring emergency surgical intervention.

So why might younger patients be more vulnerable to missed diagnoses?

The study offers one hypothesis: older patients, particularly those with reproductive experience, may be more tolerant of invasive or uncomfortable imaging procedures—particularly transvaginal ultrasonography, which is critical for detecting the eccentric gestational sac placement characteristic of IEP.

Providers may also be more inclined to pursue thorough imaging in patients perceived as higher-risk, consciously or not. This diagnostic gap raises important questions about provider bias, procedural thresholds, and imaging proficiency.

From a clinical practice perspective, the findings reinforce the importance of maintaining a high index of suspicion for IEP, particularly in younger patients who may not fit the traditional risk profile or who present with ambiguous imaging results. While the rarity of interstitial ectopic pregnancies—estimated to account for only 2-4% of all ectopics—makes them easy to overlook, their potential for life-threatening complications demands vigilance.

The study, while limited by its single-center design and modest sample size, underscores a broader challenge in obstetric care: ensuring that rare but critical conditions are not dismissed due to demographic or experiential assumptions. It also highlights a potential opportunity for improved training in sonographic recognition of IEP, particularly in emergency and primary care settings where initial presentations often occur.

As ectopic pregnancies remain a leading cause of first-trimester maternal mortality, particularly in settings with limited access to early prenatal care, studies like this emphasize the clinical value of pattern recognition—not just in pathology, but in patient presentation and provider behavior.

With further research, including larger multicenter reviews, clinicians may better understand the interplay of age, experience, and imaging thresholds in improving early diagnosis of interstitial ectopic pregnancy. Until then, the takeaway is simple but critical: in reproductive medicine, age should inform suspicion, not lower it.