Serum hCG threshold to assess medical abortion success

Abstract

Objectives: The main aim of the study was to establish a threshold for serum human chorionic gonadotropin (hCG) level that ruled out ongoing pregnancy after induced medical abortion (MA). The secondary aim was to discover risk factors for the need for uterine aspiration.

Methods: This prospective study included women who underwent MA with mifepristone–misoprostol at ≤9 weeks of gestation between 2012 and 2014. Serum hCG levels were measured 14–21 days after MA. The main outcome measure, ongoing pregnancy, was defined as the presence of an embryo with cardiac activity on transvaginal ultrasonography after MA. The receiver operating characteristic curve was plotted to determine the optimal serum hCG threshold. Risk factors for the need for uterine aspiration were calculated using multivariate logistic regression and expressed as odds ratios (ORs) with 95% confidence intervals (CIs).

Results: The study included 814 women. Mean gestational age was 46.5 ± 7.4 days for ongoing pregnancies and 44.2 ± 4.8 days for MA success (p = .43). The ongoing pregnancy rate after MA was 0.9%. A serum hCG threshold ≥900 IU/l to diagnose ongoing pregnancy gave 100% sensitivity and 81.5% specificity, compared with 85.7% sensitivity and 83.5% specificity using a threshold ≥1000 IU/l. Independent risk factors for uterine aspiration requirement were: gravidity (OR 3.8; 95% CI 1.1, 13.2; p = .001), gestational age >6 weeks (OR 6.0; 95% CI 1.8, 6.0; p = .006) and previous surgical abortion (OR 2.4; 95% CI 1.1, 5.2; p < .001).

Conclusion: Serum hCG measurement <900 IU/l, 14–21 days after MA, is an efficient strategy for excluding ongoing pregnancy after first trimester MA.

摘要

目的：本研究的主要目的是为了确立药物流产后排除再继续妊娠可能的血清绒毛膜促性腺激素（hCG）的阈值。次要研究目的寻找需要再次吸宫的危险因素。

方法：本前瞻性研究纳入2012年至2014年妊娠≤9周使用米非司酮和米索前列醇药物流产的孕妇。术后14 ∼ 21天测定血清hCG水平。主要的结局指标：继续妊娠（定义为药物流产后经阴道超声检查仍可见胎心搏动）, 利用受试者工作（ROC）曲线来确定最佳血hCG阈值。采用多因素logistic回归分析需要再次吸宫的危险因素, 并以用OR值及)95%置信区间（CIs）表示。

结果：这项研究共纳入了814名女性。药流后继续妊娠组平均妊娠时间46.5 ± 7.4天, 药流成功组平均妊娠时间44.2 ± 4.8天（p= .43）。药流后持续妊娠率是0.9%。血清hCG阈值≥900 IU/L时诊断持续妊娠的敏感性为100%, 特异性为81.5%, 而阈值采用≥1000 IU/L诊断持续妊娠的敏感性为85.7%, 特异性为83.5%。需要吸宫的独立危险因素为：妊娠次数（OR 3.8; 95% CI 1.1, 13.2; p = 0 .001）, 孕周>6周 （OR 6.0; 95% CI 1.8, 6.0; p= 0.006）及既往手术流产史（OR 2.4; 95% CI 1.1, 5.2; p < 0.001）。

结论：药物流产后14-21天时血清hCG< 900IU/ L对于早期妊娠药流术后排除继续妊娠是一种有效的方法。

Keywords:

• First trimester
• hCG
• medical abortion
• pregnancy outcome

Acknowledgements

The authors would like to thank American Journal Experts for their help in drafting the manuscript.

Disclosure statement

The authors declare that there is no conflict of interest associated with this manuscript.