News
Beware of Deep Vein Thrombosis During Pregnancy: Kyoto University Cardiology Group Reveals Two Periods of Increased Risk Through Medical Big Data Research
- December 2, 2025
A research group from the Department of Cardiology at Kyoto University analyzed venous thromboembolism (VTE, commonly known as Deep Vein Thrombosis) in pregnant Japanese women using Japan’s largest medical database held by Medical Data Vision Co., Ltd. (MDV; Chiyoda-ku, Tokyo; President: Hiroyuki Iwasaki). The analysis revealed a bimodal pattern in the timing of VTE onset, with the first peak occurring during the first trimester (up to 13 weeks of gestation) and the second peak during the third trimester (from 28 weeks onward). The study also found that, even with anticoagulant therapy, some patients experienced recurrence, bleeding events, or in-hospital death.
Prof. Yugo Yamashita
from the research group
This study was conducted by a research group led by Yugo Yamashita and Daisuke Baba from the Department of Cardiology at Kyoto University. The research paper has been published in Circulation Journal.
The original paper can be accessed here → https://www.jstage.jst.go.jp/article/circj/advpub/0/advpub_CJ-25-0124/_article
QR code of
the paper
The analyzed data from MDV hospital database included 15,472 pregnant women who may have been hospitalized for VTE between April 2008 and September 2023. After excluding patients who did not receive anticoagulant therapy or did not undergo imaging diagnostic tests, the study focused on 410 pregnant women with a confirmed diagnosis of VTE.
Recurrences of VTE, bleeding events, and in-hospital deaths
The mean age of the patients was 33 years, and the mean body mass index (BMI) was 23.8 kg/m². VTE onset by gestational week showed a bimodal distribution, with 126 cases (30.7%) occurring during the first peak and 236 cases (57.6%) during the second peak. Despite anticoagulant therapy, 17 patients (4.1%) experienced VTE recurrence within a six-month follow-up period. During the same period, there were three cases (0.7%) of bleeding events and four in-hospital deaths (1.0% of the 410 patients).
First peak: first trimester of pregnancy (up to 13 weeks) Second peak: third trimester of pregnancy (from 28 weeks onward, quoted from the paper)
Yugo Yamashita from the research group stated, “Economy class syndrome in pregnant women has generally been thought to occur mainly in the late stages of pregnancy, but this study shows that it can also happen in the early stages. Factors such as dehydration and reduced physical activity may contribute to the development of this condition. We believe the key message of this study is important not only for pregnant women but also for clinicians, including obstetricians and gynecologists, as a cautionary alert.”