Research Letter
Declaring a gestation nonviable: when 99% certainty is not enough

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Objective

The modern paradigm for diagnosing early pregnancy loss, including ectopic pregnancy, is to compare 2 human chorionic gonadotropin (hCG) values with those expected for a growing intrauterine pregnancy (IUP).1 Surveillance of women at risk has led to earlier diagnosis, successful medical management, and decreased morbidity and mortality.2 Confirmation of nonviability is imperative because the intervention for the diagnosis or treatment with uterine evacuation or methotrexate will terminate a

Study Design

The definition of a persistent pregnancy of unknown location included no definitive ultrasound evidence of intrauterine or extrauterine gestation and a plateau in hCG, defined as <30%, <50%, <75%, or <100% in 2, 3, 4, or 7 days, respectively.3 Here, 2 clinicians confirmed eligibility into the trial. Serial hCG levels from the participant were compared with levels used to assess the viability of a pregnancy.

Results

A participant was enrolled, randomized to expectant management, and later noted to have a viable gestation. A 33-year-old, G2 P1001, who conceived with use of clomiphene citrate and intrauterine insemination presented with abnormal serial hCG values of 7% in 2 days and 24% over 4 days: 86 at 4 0/7 weeks’ gestation, 92 at 4 2/7 weeks’ gestation, and 107 at 4 5/7 weeks’ gestation. All assays were performed in the same laboratory using the Roche E170 analyzer. A transvaginal ultrasound performed

Conclusion

Estimates of expected rise in hCG were generated from a normative sample of women at risk of pregnancy loss.4 Current clinical standards assessing viability of an early gestation are based on increases above the first percentile of hCG slopes for a growing IUP: >23% in 1 day and > 49% over 2 days (for values <1500 mIU/mL).4 Conversely, 99% of normal gestations will have at least this rise in hCG. Frequently, this is incorrectly interpreted as a threshold for viability.

The criteria used in this

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Cited by (6)

The authors report no conflict of interest.

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