Abstract Background A possible increasing incidence of VTE in pregnant women has been observed.(1, 2) This trend is concerning given the serious nature of VTE and its potentially severe impact on mothers, fetuses, and families. A rise in risk factors, such as advanced maternal age, higher BMI, preeclampsia and increased use of fertility treatments and cesarean sections, may be driving this trend.(3) However, their exact influence on VTE incidence remains unclear, highlighting the need for further research to evaluate prevention strategies and inform clinical practice. Purpose To investigate time-trends in the incidence of VTE among first-time pregnant women and examine trends in the prevalence of risk factors. Methods Through the Danish nationwide registries, we identified all first-time pregnant women between 1st of January 2004 and 31st of December 2023. The women were followed from beginning of pregnancy until 90 days post-partum, VTE, death, or end of study period, whichever came first. Baseline characteristics are summarized and stratified according to VTE status. The incidence of VTE (Deep vein thrombosis (DVT) and pulmonary embolism (PE)) was estimated as the number of VTE/10.000 pregnancies and stratified by calendar year. Results A total of 691,711 first-time pregnant women were identified of whom 1221 experienced a VTE (no. of PE: 380 and no. of DVT 907). Women with VTE had a higher mean age than those without (29.1 vs. 28.5, p0.001), were more frequently smokers (15.1%, vs. 13.8%, p0.001), had a higher prevalence of preeclampsia (8.8%, vs. 4.2%, p0.001), were more often obese (17.9% vs. 11.6%, p0.001), more often received a cesarean section (20.1% vs. 30.1%), and were more frequently users of fertility treatment (11.7%, vs. 7.8% p0.001). VTE incidence increased significantly from 2004 to 2023 (p for increasing trend 0.001) (Figure 1 panel A), though PE incidence had a downward trend from 2020 to 2023 (p for decreasing trend 0.001). The prevalence of risk factors (Figure 1 panel B), including age over 35 (12.7% in 2004 vs. 16.4% in 2023, p 0.001), fertility treatment (3.2% in 2004 vs. 7.3% in 2023, p0.001), preeclampsia (2.5% in 2004 vs. 4.0% in 2023, p0.001) and obesity (11.1% in 2004 vs. 15.7% in 2023, p0.001), ) increased significantly from 2004 to 2023, while the prevalence of smoking (22.0% in 2004 vs. 7.7% in 2023, p0.001) decreased significantly during the same period. The rate of cesarean sections remained stable between 2004 and 2023 (22.0% in 2004 vs. 22.7% in 2023). Conclusion We show an increased incidence of VTE among first-time pregnant women, likely linked to increased prevalence of risk factors such as advanced maternal age, higher BMI, fertility treatment, and preeclampsia. Notably, we observed a decrease in the incidence of PE after 2020, which likely reflects increased clinical vigilance and earlier diagnosis of VTE, leading to timely intervention that prevents the DVT from progressing to PE.
Sindet‐Pedersen et al. (Sat,) studied this question.