Contraindications
While combined oral contraceptives are generally considered to be a relatively safe medication, they are contraindicated for those with certain medical conditions. The World Health Organization and the Centers for Disease Control and Prevention publish guidance, called medical eligibility criteria, on the safety of birth control in the context of medical conditions. Hypercoagulability
Estrogen in high doses can increase risk of blood clots. All COCP users have a small increase in the risk of venous thromboembolism compared with non-users; this risk is greatest within the first year of COCP use. Individuals with any pre-existing medical condition that also increases their risk for blood clots have a more significant increase in risk of thrombotic events with COCP use. These conditions include but are not limited to high blood pressure, pre-existing cardiovascular disease (such as valvular heart disease or ischemic heart disease), history of thromboembolism or pulmonary embolism, cerebrovascular accident, and a familial tendency to form blood clots (such as familial factor V Leiden). There are conditions that, when associated with COCP use, increase risk of adverse effects other than thrombosis. For example, women with a history of migraine with aura have an increased risk of stroke when using COCPs, and women who smoke over age 35 and use COCPs are at higher risk of myocardial infarction. Pregnancy and postpartum
Women who are known to be pregnant should not take COCPs. Those in the postpartum period who are breastfeeding are also advised not to start COCPs until 4 weeks after birth due to increased risk of blood clots.
Laryngeal paralysis in animals is a condition in which the nerves and muscles that control the movements of one or both arytenoid cartilages of the larynx cease to function, and instead of opening during aspiration and closing during swallowing, the arytenoids remain stationary in a somewhat neutral position. Specifically, the muscle that causes abduction of the arytenoid cartilage, the cricoarytenoideus dorsalis muscle, ceases to function. This leads to inadequate ventilation during exercise and during thermoregulatory panting as well as incomplete protection of the airway during swallowing. One of the most common forms of laryngeal paralysis develops in geriatric medium to large breed dogs, in particular the Labrador retriever, but also some other breeds. This had been traditionally known as idiopathic laryngeal  paralysis ("ILP": idiopathic means "of unknown cause"), and was believed to be a result of a condition affecting the nerves of the larynx (bilateral mononeuropathy of the recurrent laryngeal nerves). However investigations into ILP by two groups in Michigan and Tennessee between 2005 - 2013 showed that the condition was not limited to, or specifically a result of, dysfunction of the laryngeal nerves. Instead it was the most visible symptom of a slowly progressing polyneuropathy of old age, which also affected other nerves in the body. This finding, now generally believed correct following further research, has led to the proposed renaming of this type of laryngeal paralysis from "Idiopathic laryngeal paralysis" ("ILP") to "Geriatric onset laryngeal paralysis polyneuropathy" ("GOLPP").