Gestation is the period of development during the carrying of an embryo, and later fetus, inside viviparous animals (the embryo develops within the parent). It is typical for mammals, but also occurs for some non-mammals. Mammals during pregnancy can have one or more gestations at the same time, for example in a multiple birth.The time interval of a gestation is called the gestation period. In obstetrics, gestational age refers to the time since the onset of the last menses, which on average is fertilization age plus two weeks. Mammals
In mammals, pregnancy begins when a zygote (fertilized ovum) implants in the females uterus and ends once the fetus leaves the uterus during labor or an abortion (whether induced or spontaneous). Humans
In humans, pregnancy can be defined clinically or biochemically. Clinically, pregnancy starts from the mothers last missed period. Biochemically, pregnancy starts when a womans human chorionic gonadotropin (hCG) levels rise above 25 mIU/mL.Human pregnancy can be divided into three trimesters, each approximately three months long: the first, second, and third trimester. The first trimester is from the last menstrual period through the 13th week, the second trimester is 14th–28/29th week, and the third trimester is 29/30th–42nd week. Birth normally occurs at a gestational age of about 40 weeks, though it is common for births to occur from 37 to 42 weeks.
The treatment must be patient specific, taking into consideration all of the previous and current health complications. The doctor that creates the treatment must have intimate knowledge of the patients health and create a treatment plan that covers all of the symptoms focusing on the most chronic areas. The first step for most with the disorder begins with some form of physical therapy in order for the patient to gain more control over the affected areas. The therapy can help patients with their posture and gain control over the areas of their body that they have the most problems with. The second step in the treatment process is medication. The medications focus on the chemicals released by neurotransmitters in the nervous system, which control muscle movement. The medications on the market today are anticholinergics, benzodiazepines, baclofen, dopaminergic agents/dopamine-depleting agents, and tetrabenazine. Each medication is started on a low dosage and gradually increased to higher doses as the disease progresses and the side effects are known for the individual. A more site-specific treatment is the injection of botulinum toxin. It is injected directly into the muscle and works much the same way the oral medications do—by blocking neurotransmitters. The injections are not a treatment for the disease, but are a means to control its symptoms. A fourth option in the treatment for the symptoms of torsion dystonia is surgery. Surgery is performed only if the patient does not respond to the oral medications or the injections.