A 2018 systematic review reported that breast density with an estrogen plus oral progesterone was significantly increased in three studies and unchanged in two studies. Changes in breast density with progesterone appear to be less than with the compared progestins.In large short-term observational studies, estrogen alone and the combination of estrogen and oral progesterone have generally not been associated with an increased risk of breast cancer. Conversely, the combination of estrogen and almost any progestin, such as medroxyprogesterone acetate or norethisterone acetate, has been associated with an increased risk of breast cancer. The only exception among progestins is dydrogesterone, which has shown similar risk to that of oral progesterone. Breast cancer risk with estrogen and progestin therapy is duration-dependent, with the risk being significantly greater with more than 5 years of exposure relative to less than 5 years. In contrast to shorter-term studies, the longer-term observations (>5 years) of the French E3N study showed significant associations of both estrogen plus oral progesterone and estrogen plus dydrogesterone with higher breast cancer risk, similarly to estrogen plus other progestogens. Oral progesterone has very low bioavailability and has relatively weak progestogenic effects. The delayed onset of breast cancer risk with estrogen plus oral progesterone is potentially consistent with a weak proliferative effect of oral progesterone on the breasts. As such, a longer duration of exposure may be necessary for a detectable increase in breast cancer risk to occur. In any case, the risk remains lower than that with most progestins.
Fractures such as a symphyseal or bilateral parasymphyseal may lead to mobility of the central portion of the mandible where genioglossus attaches, and allow the tongue to fall backwards and block the airway. In larger fractures, or those from high velocity injuries, soft tissue swelling can block the airway.In addition to the potential for airway compromise, the force delivered to break the jaw can be great enough to either fracture the cervical spine or cause intra-cranial injury (head injury). It is common for both to be assessed with facial fractures.Finally, vascular injury can result (with particular attention to the internal carotid and jugular) from high velocity injuries or severely displaced mandible fractures. Loss of consciousness combined with aspiration of tooth fragments, blood and possibly dentures mean that the airway may be threatened. Reduction
Reduction refers to approximating the ends of the bones edges that are broken. This is done with either an open technique,  where an incision is made, the fracture is found and is physically manipulated into place, or closed technique where no incision is made.The mouth is unique, in that the teeth are well secured to the bone ends but come through epithelium (mucosa). A leg or wrist, for instance, has no such structure to help with a closed reduction.