Liu Ning, Vigod Simone N, Farrugia M Michèle, Urquia Marcelo L, Ray Joel G
Institute of Health Policy Management and Evaluation, University of Toronto, Toronto, ON, Canada; Institute for Clinical Evaluative Sciences, Toronto, ON, Canada.
Institute of Health Policy Management and Evaluation, University of Toronto, Toronto, ON, Canada; Department of Psychiatry, University of Toronto, Toronto, ON, Canada; Institute for Clinical Evaluative Sciences, Toronto, ON, Canada; Women's College Hospital, Toronto, ON, Canada.
Lancet Haematol. 2018 Jul;5(7):e279-e288. doi: 10.1016/S2352-3026(18)30069-3. Epub 2018 Jun 18.
A woman's risk of venous thromboembolism during pregnancy is estimated to be two-to-six times higher than her risk when she is not pregnant. Such risk estimates are largely based on pregnancies that result in delivery of a newborn baby; no estimates exist for the risk of venous thromboembolism after induced abortion, another common pregnancy outcome. To fill this knowledge gap, we aimed to assess the risk of venous thromboembolism in women whose first pregnancy ended with induced abortion.
We did this propensity score-matched cohort study using data from the universal health-care system of Ontario, Canada. We included primigravid women who had an induced abortion between Jan 1, 2003, and Dec 31, 2015, and used a propensity score to match them to primigravid women who had a livebirth (1:1) or nulligravid women who were not pregnant on the procedure date of their matched counterpart and who did not conceive within 1 year afterwards (5:1). We excluded from our analysis women younger than 15 years or older than 49 years and individuals who had missing or invalid information about their sex, area of residence, residential income, or world region of origin. The primary outcome was risk of any venous thromboembolism within 42 days of the index date (defined as the date of an induced abortion, delivery date for livebirth, or for non-pregnant women the induced abortion date of their matched counterpart). We compared the rate of venous thromboembolism in primigravid women who had an induced abortion with the rate of venous thromboembolism in propensity-score-matched non-pregnant women and propensity-score-matched primigravid women whose pregnancy ended with a livebirth. We generated hazard ratios (HRs) of 42-day risk of venous thromboembolism after induced abortion using Cox proportional hazard models.
We identified 194 086 eligible women whose first pregnancy ended with induced abortion, of whom 176 001 (90·7%) could be matched with women whose first pregnancy ended in delivery of a newborn. These 176 001 women were also matched to 880 005 non-pregnant women. The rate of venous thromboembolism within 42 days of an induced abortion was 30·1 (95% CI 22·0-38·2) per 100 000 women compared with 13·5 (11·1-16·0) per 100 000 women in the non-pregnant group (HR 2·23, 95% CI 1·61-3·08). The HR was 0·16 (95% CI 0·12-0·22) when compared with the women in the livebirth cohort, whose venous thromboembolism rate within 42 days postpartum was 184·7 (95% CI 164·6-204·7) per 100 000 women.
The 42-day risk of venous thromboembolism after an induced abortion is double that of a matched non-pregnant woman, and is significantly lower than after a livebirth. This novel information can inform estimates of peri-procedural risk of venous thromboembolism after induced abortion. Clinicians could consider a lower threshold for ordering a diagnostic test to rule out venous thromboembolism after induced abortion than they would in a non-pregnant woman.
Institute for Clinical Evaluative Sciences.
据估计，女性在怀孕期间发生静脉血栓栓塞的风险比非孕期高两到六倍。此类风险估计主要基于那些最终分娩出新生儿的妊娠情况；对于人工流产这一另一种常见的妊娠结局后发生静脉血栓栓塞的风险，尚无相关估计。为填补这一知识空白，我们旨在评估首次妊娠以人工流产告终的女性发生静脉血栓栓塞的风险。
我们利用加拿大安大略省全民医疗保健系统的数据开展了这项倾向评分匹配队列研究。我们纳入了在2003年1月1日至2015年12月31日期间进行人工流产的初孕妇，并使用倾向评分将她们与分娩活产儿的初孕妇（1:1）或在其匹配对象的手术日期时未怀孕且在之后1年内未受孕的未孕妇（5:1）进行匹配。我们在分析中排除了年龄小于15岁或大于49岁的女性，以及那些在性别、居住地区、居住收入或原籍世界地区方面有缺失或无效信息的个体。主要结局是在索引日期（定义为人工流产日期、分娩活产儿的日期，或对于未孕妇而言其匹配对象的人工流产日期）后的42天内发生任何静脉血栓栓塞的风险。我们比较了进行人工流产的初孕妇中静脉血栓栓塞的发生率与倾向评分匹配的未孕妇以及倾向评分匹配的妊娠以分娩活产儿告终的初孕妇中静脉血栓栓塞的发生率。我们使用Cox比例风险模型生成人工流产后42天静脉血栓栓塞风险的风险比（HRs）。
我们识别出194086名首次妊娠以人工流产告终的符合条件的女性，其中176001名（90.7%）能够与首次妊娠以分娩新生儿告终的女性相匹配。这176001名女性也与880005名未孕妇相匹配。人工流产后42天内静脉血栓栓塞的发生率为每100000名女性中有30.1例（95%CI 22.0 - 38.2），而未孕组中每100000名女性中有13.5例（11.1 - 16.0）（HR 2.23，95%CI 1.61 - 3.08）。与分娩活产儿队列中的女性相比，HR为0.16（95%CI 0.12 - 0.22），分娩活产儿队列中产后42天内静脉血栓栓塞的发生率为每100000名女性中有184.7例（95%CI 164.6 - 204.7）。
人工流产后42天发生静脉血栓栓塞的风险是匹配的未孕妇的两倍，且显著低于分娩活产后的风险。这一全新信息可为人工流产后静脉血栓栓塞围手术期风险的估计提供参考。临床医生在人工流产后进行诊断性检查以排除静脉血栓栓塞时，可考虑采用比未孕妇更低的阈值。
临床评估科学研究所。
