The easiest way to explain the dangers of progestins and the vast difference between progestin and bioidentical progesterone is this:

PROGESTINS ARE NEVER GIVEN TO A PREGNANT WOMAN BECAUSE THEY ARE CONSIDERED A DRUG AND CAN CAUSE A PREGNANT WOMAN TO MISCARRY AND ALSO CAUSE GREAT COMPLICATIONS TO THE FETUS AND MOTHER. see here and here

NATURAL BIO-IDENTICAL PROGESTERONE IS GIVEN TO PREGNANT WOMEN TO HELP PREVENT MISCARRIAGE AND TO PREVENT COMPLICATIONS. see here

 

BUT HERE’S MORE:

Natural progesterone is not a drug, nor is it necessary to have a prescription to acquire this natural substance. The state of California and only the state of California does not delineate between the synthetic form of progesterone referred to as progestins which are found in most birth control medications, and the plant based, micronized progesterone which is bio-identical to the progesterone our bodies make and has science based benefits such as; supplementing pregnant women to avoid miscarriage, pre-eclampsia, lessening morning sickness and gestational diabetes and given to people with traumatic brain injury and has anti-cancer, heart, lung and brain protective benefits and management of catamenial seizures. 

Progestins have been implicated in everything from blood clots, fibroids, heart disease, high blood pressure and of all things, triggering catamenial epilepsy. The state of California therefore requires a cancer warning on ALL progesterone products, regardless of the vast scientific difference between the two. 

[Micronized progesterone is a bioidentical hormone with a molecular structure identical to that of endogenous progesterone produced by the ovary. Synthetic progestins have a different chemical structure from progesterone. These compounds mimic some of the effects of progesterone but may have different actions on progesterone receptors []. Synthetic progestins may be structurally related to progesterone (e.g., medroxyprogesterone acetate (MPA), dydrogesterone) or to testosterone (e.g., levonorgestrel, drospirenone) with differing potency and pharmacokinetics. The physiologic effects of a particular progestin depend not only on these properties but also on receptor binding. In addition to binding to progesterone receptors, these compounds may also have an affinity for androgen, glucocorticoid, and mineralocorticoid receptors [].]  SEE FULL STUDY HERE