Women are at increased risk for a venous thromboembolic event (VTE) when using CHCs, including TWIRLA. The risk of VTE may be greater in women with a BMI ≥ 30 kg/m2 compared to women with a lower BMI, and TWIRLA is contraindicated in obese patients [see Contraindications (4)]. In the Phase 3 clinical trial, four TWIRLA-treated women experienced a VTE. All of these women had a BMI > 30 kg/m2 [see Adverse Reactions (6.1)]. 

  * Stop TWIRLA if an arterial or venous thromboembolic event occurs.
  * Stop TWIRLA if there is unexplained loss of vision, proptosis, diplopia, papilledema, or retinal vascular lesions. Evaluate for retinal vein thrombosis immediately. 
  * Discontinue TWIRLA during prolonged immobilization and resume treatment based on clinical judgement. If feasible, stop TWIRLA at least 4 weeks before and through 2 weeks after major surgery or other surgeries known to have an elevated risk of thromboembolism. 
  * Start TWIRLA no earlier than four weeks after delivery in women who are not breast-feeding. The risk of postpartum thromboembolism decreases after the third postpartum week, whereas the likelihood of ovulation increases after the third postpartum week. 
  * Before starting TWIRLA, evaluate any past medical history or family history of thromboembolism or thromboembolic disorders. Consider whether the history suggests an inherited or acquired hypercoagulopathy. TWIRLA is contraindicated in women with a high risk of arterial or venous thromboembolic diseases [see Contraindications (4)]. 



Arterial Events   
CHCs increase the risk of cardiovascular events and cerebrovascular events, such as myocardial infarction and stroke. The risk is greater among older women (> 35 years of age), smokers, and women with hypertension, dyslipidemia, diabetes, or obesity.

TWIRLA is contraindicated in women over 35 years of age who smoke [see Contraindications (4)]. Cigarette smoking increases the risk of serious cardiovascular events from CHC use. This risk increases with age, particularly in women over 35 years of age, and with the number of cigarettes smoked.

Venous Events   
The use of CHCs increases the risk of VTEs, such as deep vein thrombosis and pulmonary embolism. Risk factors for VTEs include smoking, obesity, and family history of VTE, in addition to other factors that contraindicate use of CHCs. While the increased risk of VTE associated with the use of CHCs is well-established, the rates of VTE are even greater during pregnancy, especially during the postpartum period (see Figure 1). The rate of VTE in women using CHCs has been estimated to be 3 to 12 cases per 10,000 woman-years for non-oral CHCs.

The risk of VTE is highest during the first year of use of a combined oral contraceptive (COC) and when restarting hormonal contraception after a break of four weeks or longer. This initial higher risk declines during the first year, but users of CHCs remain at an increased risk of VTE compared to non-users of CHCs. Based on results from a few studies, there is some evidence that this is true for non-oral products as well. The risk of thromboembolic disease due to CHCs gradually disappears after CHC use is discontinued.

Figure 1 shows the risk of developing a VTE for women who are not pregnant and do not use hormonal contraceptives, for women who use hormonal contraceptives with a range of doses and routes of administration, for pregnant women, and for women in the postpartum period. To put the risk of developing a VTE into perspective: If 10,000 women who are not pregnant and do not use hormonal contraceptives are followed for one year, between 1 and 5 of these women will develop a VTE.

Figure 1. Likelihood of Developing a VTE Within One Year Among Pregnant and Non-Pregnant Women

  
*CHC = combination hormonal contraception  
** Pregnancy data based on actual duration of pregnancy in the reference studies. Based on a model assumption that pregnancy duration is 9 months, the rate is 7 to 27 per 10,000 WY.