Metabolic Alkalosis


The information provided below is for readers based in the United States of America. Readers outside of the United States of America should seek the information from local sources.

What is metabolic alkalosis during pregnancy?

Metabolic alkalosis is a situation in which the pH of your body fluids and other tissues is more than 7.45. Normally, pH in body fluids ranges from 7.35 to 7.45, but alkalosis can result for a variety of reasons. The kidneys may keep or generate too much of an electrolyte called bicarbonate (HCO3-) in the body, for instance, and/or too much of an electrolyte called chloride (Cl-) may be eliminated through the gastrointestinal (GI) tract, or kidneys. Elimination of acid through the GI tract also causes metabolic alkalosis, as does excretion of too much acid through the kidneys, due to a range of electrolyte and fluid disturbances. Certain medications, rare genetic conditions, excess of certain hormones, and consumption of too much calcium (such as in calcium supplements or milk) also can cause metabolic alkalosis. These and other causes can lead to metabolic alkalosis in pregnant women, but such cases are uncommon, and the main reason for metabolic alkalosis in pregnancy is vomiting. Vomiting, which causes you to lose both acid and Cl-, can occur as part of the common nausea and vomiting of pregnancy (NVP), or more intensely as part of a condition called hyperemesis gravidarum (HG). HG is a complication of pregnancy featuring severe nausea and vomiting, as well as weight loss and electrolyte disturbances, including metabolic alkalosis, typically also with dehydration.

How common is metabolic alkalosis during pregnancy?

Metabolic alkalosis is very rare in pregnancy, but when it does occur in pregnant women, it is usually a complication of vomiting. During pregnancy, vomiting occurs both as a component of NVP, which strikes mostly in the first trimester (usually beginning between 4 and 6 weeks gestation and peaking from week 8 to week 12), and also as part of HG, which tends to strike more in the middle of pregnancy. Of these two conditions, HG is more likely to cause metabolic alkalosis, because it generally involves more intense, more frequent vomiting compared with NVD. However, whereas NVD afflicts 50-90 pregnancies, HG affects only 0.5 to 3 percent of pregnancies, and only a fraction of vomiting cases lead to metabolic alkalosis. If you develop metabolic alkalosis, due to vomiting or another reason, factors that can help maintain the alkalosis include hypokalemia (low potassium), licorice ingestion, dehydration, decreased filtering of blood through kidneys, decreased chloride levels, certain medications (loop diuretics and thiazide diuretics), certain genetic conditions (Bartter syndrome and Gitelman syndrome), and excess aldosterone (a hormone that helps increase blood pressure by keeping water and sodium in the body). These conditions also can be the main cause of metabolic alkalosis.

How is metabolic alkalosis during pregnancy diagnosed?

Metabolic alkalosis is a laboratory diagnosis, but doctors can get initial clues from factors in the history of your condition, such as that you have been vomiting a lot, and nonspecific symptoms, such as muscle twitching, spasms, or tremors, numbing sensations, lightheadedness, and confusion.

Laboratory assessment of your acid-base status requires blood samples, including a standard blood sample taken from a vein and also blood taken from an artery, typically the radial artery in your arm, for a test called arterial blood gases (ABG). The pH of your blood will be tested, along with levels of electrolytes and the partial pressure of carbon dioxide (PaCO2). Doctors will be paying close attention to your HCO3- concentration, which is elevated in metabolic alkalosis (in most clinical labs, this means above 28 mEq/L), and your potassium concentration [K+], which may be too low (hypokalemia) as a result of the alkalosis (hypokalemia also can be a cause of metabolic alkalosis, but usually it is the other way around).

Does metabolic alkalosis cause problems during pregnancy?

Metabolic alkalosis can cause a varying amount of abnormalities in the heart, the nervous system, muscles, and the liver. This may give you symptoms such as muscle twitching, spasms, or tremors, numbing sensations, lightheadedness, and confusion. If your respiratory system is healthy, it will compensate partly for metabolic alkalosis by slowing the breathing rate to make you retain more carbon dioxide (CO2), which is converted to acid in body tissues.

Does metabolic alkalosis cause problems for the baby?

If your respiratory system is healthy, then generally, your lungs will compensate partly for the metabolic alkalosis, making effects on the baby unlikely. However, if the alkalosis is severe and present at the time of delivery, the neonate can be born with alkalosis, causing slowed breathing, decreased muscle tone, and a range of metabolic and organ disruptions that will require careful management in the neonatal intensive care unit.

What to consider about taking medications when you are pregnant or breastfeeding:

  • The risks to yourself and your baby if you do not treat the metabolic alkalosis
  • The risks and benefits of each medication you use when you are pregnant
  • The risks and benefits of each medication you use when you are breastfeeding

What should I know about using medication to treat metabolic alkalosis during pregnancy?

Therapy for metabolic alkalosis consists of countering the factors that are promoting the alkalosis, and, if needed, reversing the chemistry that has been pushing the acid-base balance toward higher than normal pH. Outside of pregnancy, this can be achieved with a type of medication called a carbonic anhydrase inhibitor, the main one being acetazolamide. Some concern surrounds the use of acetazolamide in pregnancy, due to laboratory animal studies showing possible risks to the fetus, but few human data are available, and the medication should be used, if needed to correct your condition. Reversal of alkalosis also can be achieved with intravenous infusion of hydrochloric acid (the same type of acid that comes out of your stomach when you vomit.) The infusion must be done very slowly and carefully to avoid overshooting and causing the opposite condition, acidosis.

Who should NOT stop taking medication for metabolic alkalosis during pregnancy?

Medications for metabolic alkalosis (acetazolamide, acid infusion) must be given in a very careful way with very precise dosing and timing, so you are not able to stop treatment on your own.

What should I know about choosing a medication for my metabolic alkalosis during pregnancy?

It is important to stay in communication with your health care provider as the release of new studies over time can change the outlook on the role of specific medications during pregnancy.

You may find Pregistrys expert reports about the medications to treat this condition here. Additional information can also be found in the sources listed below.

What should I know about taking a medication for my metabolic alkalosis when I am breastfeeding?

Acetazolamide is not thought to be harmful for nursing women.

What alternative therapies besides medications can I use to treat my metabolic alkalosis during pregnancy?

There is a procedure called low bicarbonate dialysis, in which HCO3- is pulled out of your body fluids to lower its concentration in your body.

What can I do for myself and my baby when I have metabolic alkalosis during pregnancy?

Follow th
e instructions of your physician. Cooperate with your health care providers as they work through diagnostic tests and treatments.

Resources for metabolic alkalosis in pregnancy:

For more information about metabolic alkalosis during and after pregnancy, contact (800-994-9662 [TDD: 888-220-5446]) or contact the following organizations:

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Last Updated: 01-01-2020
General information

It is very common for women to worry about having a miscarriage or giving birth to a child with a birth defect while they are pregnant. Many decisions that women make about their health during pregnancy are made with these concerns in mind.

For many women these concerns are very real. As many as 1 in 5 pregnancies end in a miscarriage, and 1 in 33 babies are born with a birth defect. These rates are considered the background population risk, which means they do not take into consideration anything about the health of the mom, the medications she is taking, or the family history of the mom or the baby’s dad. A number of different things can increase these risks, including taking certain medications during pregnancy.

It is known that most medications, including over-the-counter medications, taken during pregnancy do get passed on to the baby. Fortunately, most medicines are not harmful to the baby and can be safely taken during pregnancy. But there are some that are known to be harmful to a baby’s normal development and growth, especially when they are taken during certain times of the pregnancy. Because of this, it is important to talk with your doctor or midwife about any medications you are taking, ideally before you even try to get pregnant.

If a doctor other than the one caring for your pregnancy recommends that you start a new medicine while you are pregnant, it is important that you let them know you are pregnant.

If you do need to take a new medication while pregnant, it is important to discuss the possible risks the medicine may pose on your pregnancy with your doctor or midwife. They can help you understand the benefits and the risks of taking the medicine.

Ultimately, the decision to start, stop, or change medications during pregnancy is up to you to make, along with input from your doctor or midwife. If you do take medications during pregnancy, be sure to keep track of all the medications you are taking.