Prometrium Cardiovascular Impact Long-Term: What the Evidence Actually Shows

What the current label says about cardiovascular risk

Prometrium is oral micronized progesterone. The current label has no boxed warning. On 2026-02-12, FDA approved labeling changes for six menopausal hormone therapy products, including Prometrium, that removed cardiovascular disease, breast cancer and probable dementia statements from the boxed warning [5][6]. The cardiovascular content of the label did not disappear.

The Warnings section still states that the safety and efficacy of estrogen plus progestogen for prevention of cardiovascular disorders has not been established, and it summarizes the Women's Health Initiative results for conjugated estrogens 0.625 mg plus medroxyprogesterone acetate 2.5 mg [2]. The label says the relevance of those WHI findings to lower doses, other routes, or other estrogen plus progestogen products is not known [2].

The label also carries its own cardiovascular boundaries. Active DVT or PE, a history of DVT or PE, active arterial thromboembolic disease such as stroke or MI, or a history of these conditions are contraindications [2]. The label says to stop Prometrium immediately if PE, DVT, stroke or MI occurs or is suspected, and if feasible to stop at least 4 to 6 weeks before surgery associated with increased thromboembolism risk or during prolonged immobilization [4]. It warns that progesterone may cause some fluid retention and that women with cardiac or renal dysfunction warrant careful observation [2].

PEPI: the main randomized comparison of progestins

The Postmenopausal Estrogen/Progestin Interventions trial randomized 875 healthy postmenopausal women aged 45 to 64 to five groups for three years: placebo, conjugated equine estrogen 0.625 mg/day alone, CEE plus cyclic medroxyprogesterone acetate 10 mg/day for 12 days a month, CEE plus continuous MPA 2.5 mg/day, or CEE plus cyclic micronized progesterone 200 mg/day for 12 days a month [1]. The placebo group received no hormones [1]. The primary endpoints were HDL cholesterol, systolic blood pressure, serum insulin and fibrinogen [1].

HDL-C changes separated the regimens. Mean HDL-C fell 0.03 mmol/L with placebo, rose 0.14 mmol/L with CEE alone, rose 0.11 mmol/L with CEE plus micronized progesterone, and rose 0.03 to 0.04 mmol/L with the two MPA regimens [1]. The trial report describes the HDL-C changes as three statistically distinct groups [1].

That is a cholesterol result, not a heart-attack result. PEPI was designed to compare risk factors over three years, not to count myocardial infarctions or strokes [1].

WHI: why its heart numbers are not Prometrium numbers

The WHI trial enrolled 16,608 women aged 50 to 79 and compared conjugated estrogens 0.625 mg plus medroxyprogesterone acetate 2.5 mg daily with placebo. The trial publication reported a mean follow-up of 5.2 years [3]; the Prometrium label summarizes the results over an average of 5.6 years [2]. MPA, not micronized progesterone, was the progestin [2][3].

The Prometrium label summarizes the WHI results as relative risks of 1.18 for coronary heart disease (95% CI 0.95 to 1.45), 1.37 for stroke (95% CI 1.07 to 1.76), 1.98 for pulmonary embolism (95% CI 1.36 to 2.87) and 1.87 for deep vein thrombosis (95% CI 1.37 to 2.54) [2]. In the 50-to-59 age subgroup, the label reports a CHD relative risk of 1.34 (95% CI 0.82 to 2.19) and a stroke relative risk of 1.51 (95% CI 0.81 to 2.82) [2].

The label itself says that only daily oral CE 0.625 mg and MPA 2.5 mg were studied in the WHI estrogen-plus-progestin trial, so the relevance of the findings to other doses, routes or products is not known, and it is not possible to definitively exclude or quantify those risks for other products [2].

Venous thromboembolism: the ESTHER case-control data

ESTHER was a French multicenter case-control study of women aged 45 to 70, conducted between 1999 and 2005, with 271 cases of a first idiopathic VTE and 610 matched controls [7]. Compared with nonusers, oral estrogen was associated with an adjusted odds ratio for VTE of 4.2 (95% CI 1.5 to 11.6); transdermal estrogen had an odds ratio of 0.9 (95% CI 0.4 to 2.1) [7].

Micronized progesterone was not significantly associated with VTE (OR 0.7, 95% CI 0.3 to 1.9), while norpregnane derivatives were associated with a fourfold increase (OR 3.9, 95% CI 1.5 to 10.0) [7]. This is observational data and cannot establish cause and effect. The Prometrium label still contraindicates active or prior DVT or PE [2].

Early versus late menopause: KEEPS and ELITE

KEEPS randomized 727 healthy women aged 42 to 58 who were 6 to 36 months past their last menses, had a coronary artery calcium score below 50 and had not used estrogen or lipid-lowering therapy for at least 90 days [8]. They received oral conjugated equine estrogen 0.45 mg/day, transdermal 17-beta-estradiol 50 mcg/day, each with oral progesterone 200 mg for 12 days a month, or placebo for 48 months [8]. Mean carotid intima-media thickness increased 0.007 mm/year and was similar across groups; blood pressure did not change with either active estrogen, and the trial concluded that four years of early hormone therapy did not affect atherosclerosis progression [8]. Oral progesterone was given with both active estrogen arms, so KEEPS cannot separate progesterone's effect from estrogen's [8].

ELITE stratified 643 healthy postmenopausal women by time since menopause: less than 6 years or 10 or more years [9]. They received oral 17-beta-estradiol 1 mg/day, with progesterone vaginal gel 45 mg sequentially for women with a uterus, or placebo, for a median of 5 years [9]. Among women less than 6 years past menopause, CIMT increased 0.0078 mm/year with placebo versus 0.0044 mm/year with estradiol (P=0.008). Among women 10 or more years past menopause, the rates were 0.0088 and 0.0100 mm/year (P=0.29); the interaction P value was 0.007 [9]. The progesterone in ELITE was a vaginal gel, not Prometrium capsules. Both trials used imaging endpoints rather than clinical cardiovascular events [8][9].

What this means for the long-term question

For Prometrium itself, the direct randomized evidence stops at risk factors and imaging. In PEPI, HDL-C rose by 0.11 mmol/L with CEE plus cyclic micronized progesterone, compared with 0.14 mmol/L with CEE alone and 0.03 to 0.04 mmol/L with the MPA regimens [1]. Whether that difference changes heart attack or stroke rates over 10 or more years is not answered by PEPI, KEEPS or ELITE, which did not measure those events as outcomes [1][8][9].

ESTHER found no significant VTE association with micronized progesterone, but it is a case-control study [7]. KEEPS and ELITE address the timing of estrogen therapy [8][9].

The label gives the practical safety boundaries: active or prior DVT, PE, stroke or MI are contraindications, and fluid retention warrants caution in women with cardiac or renal dysfunction [2].