Pregnancy and Electrolyte Imbalances

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Electrolytes are ions that are dissolved in your body fluids. Ions are atoms and molecules that carry a net positive or negative electrical charge. Thus, they enable body fluids and tissues to conduct electricity. In clinical medicine, when doctors order an electrolyte panel, or “lytes”, the laboratory gives them values for the concentrations of four electrolytes: sodium (Na+), potassium (K+), chloride (Cl) and bicarbonate (HCO3) in serum (the liquid portion of a blood sample that has clotted). Typically, the four “lytes” are provided as part of a basic metabolic panel (BMP), also known as a “chem-7”, which also includes concentrations of glucose (blood sugar), blood urea nitrogen (BUN), and creatinine. Another electrolyte, calcium (Ca2+), can be added to the BMP (“chem-8”) and is automatically included in a larger panel called a comprehensive panel (CMP) or a “chem-14”. Clinically important electrolytes also include magnesium (Mg2+) and phosphate (PO43−).

The term electrolyte imbalance refers to any condition in which the concentration of one of more electrolytes is too high or too low, in one or more of the body fluid compartments. The main compartments are the intracellular (the fluid inside body cells), interstitial (fluid between body cells), and intravascular (the blood). The concentrations of each electrolyte is normally very different between these three compartments, especially between the intracellular fluid, which makes of 60 percent of the body fluid, and the extracellular fluid (the intravascular plus the interstitial fluid) and much of the function of body cells depends on those differences. Consequently, if electrolyte concentrations get thrown out of whack, there is a major impact on physiology, with certain functions and organs being particularly sensitive changes in the balance of particular electrolytes.

Electrolyte imbalances related to pregnancy are particularly common in cases of hyperemesis gravidarum. This condition features severe nausea and vomiting, with weight loss and liver problems and occurs in 0.3-3 percent of pregnancies, although incidence rises to as high as 10 percent in some populations of Asian and Middle Eastern women. Incidence also is high among young, non-Caucasian women during their first pregnancies. Additionally, there are particular conditions that put you at elevated risk for electrolyte imbalances, whether you are pregnant or not. For instance, if you have had your thyroid gland removed (total thyroidectomy), there is a small chance that small glands called the parathyroid glands were removed, or damaged, in the process of removing the thyroid. This leads to low calcium levels in the blood, called hypocalcemia. Various medications also can cause electrolyte imbalances.

Abnormal concentrations of clinically important electrolytes, such as potassium, sodium, magnesium, or calcium can cause a range of symptoms and signs, such as muscle spasms, cramps, and twitching, fatigue, seizures, numbness and pins and needle sensations, blood pressure changes, urinary frequency and urgency, nausea, vomiting, dry mouth, confusion, irritability, constipation and abnormalities of the heartbeat (which may be felt as palpitations). Some electrolyte disturbances can cause problems particular to pregnancy. An example is hypokalemia (low potassium), which causes numbness and weakness or full paralysis. There is plenty of overlap in effects between imbalances of different electrolytes. If severe enough, such disturbances can lead to coma and death. Certain electrolyte imbalances can put the life of the fetus in danger by putting the mother’s life in danger. An example is hypokalemia at a severe level (serum potassium below 2.5 mmol/L).

The presence of one electrolyte disturbance often is connected with disturbances of another electrolyte. Hypokalemia (low potassium), for instance, often occurs as a result of hypomagnesemia (low magnesium). Low potassium levels also can occur as a cause or result of an acid-base disturbance called metabolic alkalosis, which features elevated bicarbonate and can have abnormalities in the level of chloride. The causes and effects of electrolyte imbalances depend on whether an electrolyte normally has a high concentration inside cells and a low concentration outside cells, or visa versa. In the case of sodium, concentration is high in the blood, so small changes in blood concentration of sodium don’t have major effects. Loss of large amounts of body water (dehydration) is the main cause of elevated levels of elevated sodium levels in the blood (hypernatremia). The opposite, hyponatremia (lower than normal sodium in the blood) occurs when the blood is diluted due to the retention of too much water. In contrast, potassium is highly concentrated inside cells and is at low concentration in the blood. This means that very small changes in blood potassium concentration cause profound changes in how your body works. It also means that the changes in potassium can develop from a variety of processes.

During pregnancy, imbalances of potassium are a particular concern, because potassium levels can change in response to vomiting and diarrhea, which are common during pregnancy. Such chances in potassium concentration affects the rhythm of the heart. Magnesium is also important to understand in relation to pregnancy, because this electrolyte helps to calm muscles and nerves. For this reason, magnesium is given, in the form of magnesium sulfate, to stop and prevent seizures that occur in the setting of a severe pregnancy complication called eclampsia.

Doctors diagnose electrolyte imbalances with blood tests, such as the basic metabolic panel, with or without calcium, or the comprehensive metabolic panel. If doctors also need to look at your acid-base balance, you may need to supply blood from an artery for a test called arterial blood gases (ABG). Testing of the electrical activity of your heart with electrocardiography (ECG) also can be helpful, because ECG can reveal certain features associated with certain electrolyte imbalances, such as hypokalemia (low potassium) and hyperkalemia (high potassium).

Treatment depends greatly on the type of electrolyte imbalance and its underlying cause. When the concentration of a particular electrolyte is only modestly low, the woman can be given supplements of the electrolyte to take orally. These supplements are not harmful either to a fetus, or to a nursing infant. Many mild electrolyte imbalances can be corrected with oral rehydration therapy in which you take fluids with electrolytes by mouth. More severely low levels may require intravenous administrated of the electrolyte. In other cases, the treatment can be to switch a medication, such as replacing a type of diuretic (a drug that helps you eliminate water through the kidneys) with another type of diuretic that enables the kidneys to retain potassium, rather than excrete it. Typically, management of an electrolyte balance goes hand in hand with management of the woman’s fluids by way of intravenous administration of fluids with particular concentrations of sodium and glucose.

David Warmflash
Dr. David Warmflash is a science communicator and physician with a research background in astrobiology and space medicine. He has completed research fellowships at NASA Johnson Space Center, the University of Pennsylvania, and Brandeis University. Since 2002, he has been collaborating with The Planetary Society on experiments helping us to understand the effects of deep space radiation on life forms, and since 2011 has worked nearly full time in medical writing and science journalism. His focus area includes the emergence of new biotechnologies and their impact on biomedicine, public health, and society.

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