**3. Risk factors for VTE in pregnancy and puerperium**

Some groups of women have a higher risk of developing VTE. The most important individual risk factor for VTE in pregnancy is a personal history of thrombosis without a trigger factor and/or following use of estrogen-based hormonal therapy. For women who have had a previous thrombosis in pregnancy, the risk of VTE increases considerably in subsequent pregnancies if antenatal thromboprophylaxis is not used, with an estimated increased risk of recurrence of three- to four-fold [1–4].

Another important individual risk factor for VTE in pregnancy is the presence of an inherited or acquired thrombophilia (a condition that predisposes individuals to developing thromboses) [2–4].

The risk of a thromboembolic event occurring during pregnancy has been shown to differ according to the nature of the thrombophilia, with estimates of risk varying from 5–33% (Homozygotic mutations or multiple thrombophilias) [3, 7, 8].

Other pregnancy-related factors shown to increase the risk of VTE include multiple gestation, pregnancy induced hypertension, prolonged active fase of labour and cesarean section (mainly in the emergency and or after labor). In a case– control study the overall risk of VTE was 0.09%, with a higher risk of events in the postnatal period following cesarean birth; and the authors verified that the risk in the antenatal period was estimated as 0.18% following cesarean section compared with 0.03% without cesarean section [2, 6, 7].

#### *VTE Prophylaxis in Cesarean Section DOI: http://dx.doi.org/10.5772/intechopen.98974*

Obesity, smoking, advanced maternal age, severe heart disease, sickle cell disease, inflammatory bowel disease, active cancer, family history of VTE, and prolonged immobilization are other commonly reported risk factors [2].

VTE risk factors vary in their association with but appear to be common. In a recently published cross-sectional study of prospectively collected data from 21 019 sequential postpartum VTE risk assessments in a hospital setting the most prevalent VTE risk factors related to maternal and delivery characteristics included overweight and obesity (36%), age ≥ 35 (35%) and cesarean section (32%). Over three-quarters of women had at least 1 VTE risk factor (78%), and over 40% had multiple (2 or more) VTE risk factors. An important finding is the fact that in 19% of women all VTE risk developed during delivery or in the post-partum period (and were not present prior to the peripartum period) highlighting the critical importance of performing continuos VTE risk assessment even after delivery [8, 9].

COVID-19 is new disease with potentially impact in pregnancy and pueperium. The evidence addressing the issues of coagulopathy and thrombosis in pregnancy in association with COVID-19 is sparse and so far, there is no available high-quality studies at this moment. However, given the possible association between the hypercoagulability characteristic of pregnancy and the risk increase in COVID-19-related VTE, the International Society of Thrombosis and Haemostasys (ISTH), as well as the Ministry of Health in Brazil, suggest that all pregnant and postpartum women admit had at the hospital for COVID-19 (i.e., severe and moderate cases) receiving pharmacological prophylaxis [10, 11].
