Metabolic Acidosis


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.

p>What is metabolic acidosis during pregnancy?

Metabolic acidosis is a situation in which the pH of your body fluids and other tissues is less than 7.35, due to the body either losing too much of an electrolyte called bicarbonate (HCO3-) or producing excessive acid on account of abnormalities of metabolism. To discuss metabolic acidosis, we need to touch upon two math-oriented concepts. One concept is pH, which normally ranges from 7.35 to 7.45 when measured in blood samples, but urine pH has a much wider normal range. The other concept is called the anion gap (AG). Also measured in samples of blood and urine, the AG is the difference between the sum of the concentrations of the positive electrolytes, also known as cations, and the negative electrolytes, also known as anions. Normally, cations slightly outnumber anions – thats why its called an anion gap, but if the AG is very big, this is called a high AG. Its the basis for categorizing metabolic acidosis into two broad categories: high anion gap metabolic acidosis (HAGMA) and normal anion gap metabolic acidosis (NAGMA).

Terminology can be very confusing. Sometimes you will hear the terms hyperchloremic metabolic acidosis and non-anion gap metabolic acidosis used interchangeably with NAGMA, as there is overlap in the meaning of the terms, but the overlap is not perfect. Hyperchloremia abnormally high levels of chloride (Cl-), sometimes can occur with HAGMA. At the same time, the term non-anion gap technically means that the value of the AG is zero, meaning that it is too low.

Causes of HAGMA include ketoacidosis (which can occur as a complication of type 1 diabetes, starvation, and alcohol abuse), lactic acidosis (which can occur with liver disease, certain kidney conditions, certain medications, alcohol abuse, excessive exercise, ingestion of certain toxins, and also as a diabetic complication), and certain types of kidney failure. NAGMA results from the excessive loss of bicarbonate from the body due to diarrhea and certain kidney conditions.

Metabolic acidosis also can develop as a complication of certain electrolyte disturbances (such as abnormally high potassium hyperkalemia), iron overload, deficiencies of vitamins involved in the breakdown of sugar to produce energy, and from certain cancers that produce large amounts of cells that produce lactic acid.

 How common is metabolic acidosis during pregnancy?

Although metabolic acidosis is common in patients who suffer from acute illness, it is rare during pregnancy. Reported cases of HAGMA during pregnancy have resulted from uncontrolled diabetes and starvation. In contrast, NAGMA has been reported in pregnancy as a result of renal tubular acidosis (RTA), a kidney condition that can worsen during pregnancy. As noted earlier, NAGMA also can result from a severe case of diarrhea, which can happen during pregnancy, just as it can happen in the non-pregnant population.

How is metabolic acidosis during pregnancy diagnosed?

Metabolic acidosis is very much a laboratory diagnosis. Still, doctors can get initial clues from factors in the history of your condition, such as that you have been suffering from severe diarrhea, and findings on the physical examination, such as rapid breathing. Known as Kussmaul breathing, the rapid breathing results from your body compensating for metabolic acidosis by accelerating the elimination of carbon dioxide (CO2) through the lungs, which decreases the amount of acid in the body. The classic reason for Kussmaul breathing is ketosis, the presence of certain chemical compounds in the blood. Known classically as ketone bodies, the compounds include acids, notably beta-hydroxybutyric acid, which is not a ketone, but it contributes greatly to acidosis. Ketone bodies also include acetone, which is not an acid, but it is a ketone and has a very obvious fruity smell. Thus, acetone breath functions as an indicator for the accumulation of beta-hydroxybutyric acid and other acids, suggesting either starvation or uncontrolled diabetes.

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). Distinguishing between HAGMA and NAGMA requires the calculation of the AG. Your doctor may do the calculation, but typically it is performed by the lab, overseen by a laboratory medicine physician. As noted above, AG is the difference between cations and anions in the blood. Typically, just the sodium concentration [Na+], with or without the potassium concentration [K+] added, is used to represent the cations, while the sum of the Cl- + HCO3- concentrations is used for the anions.

Thus, in equation form, AG = (Na+ + K+) (Cl- + HCO3-). However, there are various other electrolytes as well as charged proteins in the blood that require adjustments to the AG calculation in certain situations. Furthermore, there are some major differences between electrolyte analyzers used in different labs. For all these reasons, there are variations on what the normal range is for AG. A good rule of thumb is that an AG coming out higher than 20 mmol/L is a high AG, meaning that the metabolic acidosis is HAGMA. On the other hand, if the AG comes out lower than 20, then the details regarding the analyzer machines and how the AG was calculated become important for determining whether your metabolic acidosis is NAGMA or HAGMA.

Does metabolic acidosis cause problems during pregnancy?

Metabolic acidosis can cause a range of problems including hyperkalemia (elevated potassium levels, which is both a cause and result of metabolic acidosis), which can have life-threatening effects on the heartbeat, loss of muscle mass, worsening of chronic kidney disease, and, over the long term, osteoporosis (decrease in bone mass, which can lead to fractures).

Does metabolic acidosis cause problems for the baby?

If your respiratory system is in good shape, then your body will partially compensate for metabolic acidosis by increasing the breathing rate, which will bring your pH in the direction back toward normal. This is called compensated metabolic acidosis, and it means that much of the excess acidity, due either to increased acid production or the elimination of bicarbonate is getting buffered fairly well. To be sure, there is concern that severe maternal acidosis, especially, when it is ketoacidosis (the type of metabolic acidosis resulting from starvation and uncontrolled diabetes) may cause acidosis in the fetus and also reduce the amount of oxygen reaching the fetus. However, very few cases of maternal acidosis have been documented, and typically when it occurs, efforts are made to deliver the baby early and avoid harmful effects in the baby.

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 acidosis
  • 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 acidosis during pregnancy?

The treatment
for metabolic acidosis is to infuse a base, sodium bicarbonate intravenously. This must be done gradually and very carefully, with frequent monitoring of your acid-base status. It does not affect the fetus, because sodium and bicarbonate are normal components of your blood, and the base entering your blood is absorbed into pH buffer systems. These buffer systems are repositories of chemicals that participate in chemical reactions that continuously move back and forth in two directions in a way that prevents abrupt changes in pH when acids or bases enter the body.  

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

Treatment for metabolic acidosis involves the administration of sodium bicarbonate. This is done intravenously, with particular timing, and in concert with management of other electrolytes and fluids, so it is not something that you can or should stop on your own.

What should I know about choosing a medication for my metabolic acidosis 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 acidosis when I am breastfeeding?

Lactation places a strong metabolic demand on your body that can exacerbate metabolic acidosis, particularly if it is related to starvation ketosis. Consequently, a woman who develops metabolic acidosis during late pregnancy or just after delivering would likely be advised not to nurse the baby.

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

You can decrease the risk of developing both ketoacidosis and lactic acidosis by drinking enough water and other fluids to keep hydrated, avoiding alcohol (which should be avoided for various other reasons during pregnancy), and managing your diabetes well.

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

Follow the instructions of your physician. Cooperate with your health care providers as they work through diagnostic tests to determine the underlying cause of your acidosis.

Resources for metabolic acidosis in pregnancy:

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

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Last Updated: 31-12-2019
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.