Our primary objective is to verify or refute a 2013 study by Connolly et al. which showed that in early pregnancy, a gestational sac was visualized 99% of the time on transvaginal ultrasound when the HCG level reached 3510 mIU/mL. Our secondary objective was to make clinical correlations by assessing the relationship between human chorionic gonadotropin (HCG) level in early pregnancy when a gestational sac is not seen and pregnancy outcomes of live birth, spontaneous abortion, and ectopic pregnancy. This retrospective study includes 144 pregnancies with an outcome of live birth, 87 pregnancies with an outcome of spontaneous abortion, and 59 ectopic pregnancies. Logistic regression is used to determine the probability of visualizing a gestational sac and/or yolk sac based on the HCG level. A gestational sac is predicted to be visualized 50% of the time at an HCG level of 979 mIU/mL, 90% at 2421 mIU/mL, and 99% of the time at 3994 mIU/mL. A yolk sac was predicted to be visualized 50% of the time at an HCG level of 4626 mIU/mL, 90% at 12,892 mIU/mL, and 99% at 39,454 mIU/mL. A total of 90% of ectopic pregnancies presented with an HCG level below 3994 mIU/mL. These results are in agreement with the study by Connolly et al. Since most early ectopic pregnancies had an HCG value below the discriminatory level for gestational sac visualization, other methods for the evaluation of pregnancy of unknown location such as repeat HCG values are clinically important.

我们的主要目标是验证或反驳 Connolly 等人 2013 年的一项研究。结果表明，在怀孕早期，当 HCG 水平达到 3510 mIU/mL 时，99% 的时间在经阴道超声检查中都能看到孕囊。我们的次要目标是通过评估未看到孕囊的妊娠早期人绒毛膜促性腺激素 (HCG) 水平与活产、自然流产和宫外孕妊娠结局之间的关系来建立临床相关性。这项回顾性研究包括 144 例活产妊娠、87 例自然流产妊娠和 59 例宫外孕。 Logistic 回归用于根据 HCG 水平确定孕囊和/或卵黄囊可视化的概率。当 HCG 水平为 979 mIU/mL 时，预计有 50% 的时间可以看到孕囊；当 HCG 水平为 2421 mIU/mL 时，预计有 90% 的时间可以看到孕囊；当 HCG 水平为 3994 mIU/mL 时，则有 99% 的时间可以看到孕囊。当 HCG 水平为 4626 mIU/mL 时，预计卵黄囊可见率为 50%；HCG 水平为 12,892 mIU/mL 时，卵黄囊可见率为 90%；HCG 水平为 39,454 mIU/mL 时，卵黄囊可见率为 99%。总共 90% 的宫外孕的 HCG 水平低于 3994 mIU/mL。这些结果与 Connolly 等人的研究一致。由于大多数早期异位妊娠的 HCG 值低于孕囊可视化的辨别水平，因此评估未知位置妊娠的其他方法（例如重复 HCG 值）在临床上很重要。