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A coma is a state of unconsciousness but deeper than sleep and usually lasting longer. Often, coma is caused either by injury, especially traumatic brain injury, or by prolonged disease. However, coma also can also be induced intentionally by doctors to protect the brain in certain situations. Examples of medical conditions that can lead to coma include strokes, ongoing seizures, diabetes (when it is not controlled and blood sugar level gets extremely high, or extremely low), infections, and tumors. Certain toxins and various situations causing a lack of oxygen reaching the brain. These situations include the loss of blood flow through the brain, cardiac arrest (lack of effective pumping of the heart), and drowning.
During pregnancy, coma can develop from any of the same reasons that it develops in non-pregnant people, but it also can result from certain severe complications of pregnancy, such as preeclampsia and eclampsia, HELLP syndrome, gestational hypertension (high blood pressure of pregnancy), and from strokes resulting from changes that pregnancy produces in the body. Additionally, pregnant women are vulnerable to developing blood clots in the spaces where blood from the veins in the brain collects, and such clots can cause coma, as can organ failure resulting from certain pregnancy complications.
The chance of developing coma during pregnancy is elevated compared with the chance in women of your own age because pregnancy entails some risk factors for conditions that can cause coma. Pregnancy carries an elevated risk to form blood clots in deep veins, for instance, which can lead to emboli, clots that travel through the veins. This can lead to pulmonary embolism (a clot in the lungs), but in some women (those who have what doctors call a patent foramen ovale [PFO]), emboli can travel from the right to the left side of the heart and get to the brain, causing an embolic stroke. Strokes occurring in the brain stem as well as strokes involving blood vessels that supply large fractions of the cerebral cortex can cause coma. Preeclampsia, a complication of pregnancy that features high blood pressure and problems with an internal organ (usually the kidneys), quadruples the risk of stroke. Diabetic coma (coma due to diabetes), can occur just as easily in pregnant women with uncontrolled diabetes as with non-pregnant women with the same condition. However, gestational diabetes (diabetes that develops only due to pregnancy) never leads to coma.
Overall, coma is extremely rare during pregnancy. In fact, when it occurs, it typically is the subject of a news report. Such cases have included women who became pregnant while comatose, in which case caretakers have been implicated.
Coma is diagnosed by assessing the person’s level alertness and neurological responsiveness. This is done by assigning various body functions a number rating as criteria that are added together on a rating system. The most common system is called the Glasgow Coma Scale (GCS), which is based on assessment of eye opening, verbal responses, and motor response. On the GCS, a score of 8 or below is considered severe, 9-12 is moderate, and 13-15 is mild. Other rating systems relevant to coma include the cerebral performance category (CPC), which is used to assess patients after cardiac arrest (the heart stops). Electrical activity of the brain is assessed with a procedure called electroencephalography (EEG). Assessment of a comatose patient also typically includes various laboratory tests on samples of blood, cerebrospinal fluid (the fluid around the brain and spinal cord), and urine, and brain imaging, such as magnetic resonance imaging (MRI) or computed tomography (CT) scanning. During pregnancy, MRI is preferred over CT, because CT exposes the woman to ionizing radiation. Doctors also conduct various imaging tests of internal organs.
As for the fetus of a comatose pregnant woman, the prognosis depends on the underlying cause of the coma. Trauma affecting blood supply to the womb and severe organ dysfunction in the mother, for instance, all put the life and health of the fetus at extreme risk. On the other hand, if the mother’s body functions are close to normal with the cause of the coma located in the brain, it is possible for the pregnancy to continue all the way to term, although such cases are very rare.
Once the condition leading to the coma has been treated, a great deal of the management consists of monitoring the woman with equipment and neurological examinations and maintaining fluid support and nutrition. In certain cases of traumatic brain injury, cardiac arrest, and other conditions, coma can be induced to protect against brain injury, sometimes using drugs and sometimes by reducing the body temperature (therapeutic hypothermia). Such comas are easily reversible.