What is hypoxia during pregnancy?
Technically, the term hypoxia either refers to a low supply of oxygen (O2) in the environment which happens when you are on a mountain or flying in an aircraft where the O2 partial pressure is significantly lower than what it is at sea level, or it refers to a low concentration of O2 in a body tissue. In practice, hypoxia in tissues throughout the body is used interchangeably with hypoxemia, meaning a lower-than-normal amount or concentration of O2 in arterial blood, defined based on either the O2 partial pressure in arterial blood (PaO2) or the percentage of hemoglobin (Hb) that is carrying O2 (called oxygen saturation or O2 sat). For a person breathing sea-level air, which has a total pressure of 760 mmHg and an O2 partial pressure of 160 mmHg, PaO2 normally ranges from 75 or 80 mmHg up to 100 or 105 mmHg. This means that you will be considered hypoxic, if your PaO2 is below 75 or 80 mmHg, depending on which lab tests your arterial blood. O2 saturation is normally above 95 percent (usually, its at least 97 percent). People below 90 percent are always called hypoxic, but sometimes values from 90-94 percent are called hypoxic, or mildly hypoxic.
As noted above, the terms hypoxia and hypoxemia are often used interchangeably. This is because hypoxemia makes your body tissues hypoxic and also because the blood is the easiest tissue in which to measure O2 concentration and pressure. Hypoxemia (and thus tissue hypoxia) can result from environmental hypoxia, such as being at high altitude. This includes flying in an aircraft, in which cabins are typically pressurized to the equivalent of being outside at an altitude of 1,8002,400 meters (6,000-8,000 feet), depending on the aircraft type. Lung problems and congenital heart defects (particularly when blood is shunted from the right side of the heart to the left side without going through the lungs) also cause hypoxia in the body. An example of a lung problem that is particularly relevant to pregnancy is pulmonary embolism (PE), a life-threatening condition that can result as a complication of venous thrombosis (clotting in a deep vein), which can happen due to increased clotting tendency and slowed venous blood flow during pregnancy.
Another category of hypoxia is that caused by poisons, such as carbon monoxide (CO), which causes hypoxemia and generalized hypoxia (hypoxia throughout body tissues) and cyanide, which causes intracellular hypoxia (hypoxia within cells). Various medications and other agents can cause a condition called methemoglobinemia in which O2 does not bind well with Hb. Finally, there is anemia, in which you can be hypoxemic and hypoxic, even though the PaO2 will be normal. Rather than being a problem of getting O2 into the body, anemia means that there is an abnormally low capacity for carrying O2 in the blood. Anemia, due to iron deficiency, is common during pregnancy, but usually, it is mild anemia. On the other hand, within the realm of tissue hypoxia is a condition particular to pregnancy called intrauterine hypoxia hypoxia in the womb which can develop from a variety of problems in the mother, the placenta, or the fetus.
How common is hypoxia during pregnancy?
Your body adjusts to the increased need for O2 delivery to tissues, including the placenta and the attached fetus, through substantial increases in the amount of blood. This often causes mild anemia, since the blood volume increases more than the amount of RBCs, but generally, tissues become hypoxic only in those women who suffer from certain medical conditions whose effects are exacerbated by pregnancy, such as congenital heart disease, or a respiratory disease, such as asthma. Factors that substantially elevate your risk of hypoxia include smoking and traveling to high altitude locations, plus factors that increase your risk of venous clotting; these factors include pregnancy itself, but also include smoking. As for intrauterine hypoxia, the risk for this category of conditions is elevated with certain pregnancy complications, particularly preeclampsia, as well as being pregnant for the first time, and smoking.
How is hypoxia during pregnancy diagnosed?
A woman who is suffering from generalized hypoxia may be cyanotic, meaning that her skin and mucous membranes will show a bluish discoloration. Much more specific information can be obtained through pulse oximetry, which is taken with a device that is clipped to your finger that measures your O2 saturation. PaO2 is measured from a sample of your arterial blood if your doctor orders an arterial blood gas (ABG) test. If you are being evaluated for anemia related to pregnancy, testing will include a complete blood count (CBC) and iron studies.
Does hypoxia cause problems during pregnancy?
The nature and severity of problems related to hypoxia depend on the amount of hypoxia and the underlying cause, which, as noted above, are numerous.
Does hypoxia cause problems for the baby?
If intrauterine hypoxia develops, this leads to intrauterine growth restriction (IUGR), meaning that the fetus is underweight and also small-for-gestational-age (SGA). This, in turn, is associated with a variety of problems that include delayed brain development and cognitive problems during childhood.
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 hypoxia
- 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 hypoxia during pregnancy?
Hypoxemia, or generalized by hypoxia, is treated with 100 percent O2 given through a nasal cannula or a mask. This is extremely effective and carries no risk for the fetus; in fact, it helps the fetus by reducing the risks of hypoxia. 100 percent O2 can be administered whether your hypoxia is due to a medical condition or injury or to being at altitude although the treatment is called 100 percent O2, nasal O2 versus masks of different types masks supply different percentages of O2 into your lungs, because of room air (which is only 21 percent O2) entering through your mouth and/or nose, except in the case of certain masks.
Who should NOT stop taking medication for hypoxia during pregnancy?
If your O2 saturation is below 90 percent, you certainly remain on 100 percent O2. When you are above 90 percent, it depends on the discretion of the doctor and a variety of other factors.
What should I know about choosing a medication for my hypoxia 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 hypoxia when I am br
You can be on O2 through a nasal cannula or a mask while you are breastfeeding.
What alternative therapies besides medications can I use to treat my hypoxia during pregnancy?
O2 from a tank, given through a nasal cannula or a mask is sometimes called medication and sometimes not. If you are mildly hypoxic due to environmental conditions that can be easily changed, such as being in a stuffy room with a lot of people, simply going outside for fresh air can help. In other circumstances, such as intrauterine hypoxia as a complication of preeclampsia, the treatment is to deliver the baby as early as possible. This typically entails some medication, namely a corticosteroid, to speed the maturation of the fetal lungs.
What can I do for myself and my baby when I have hypoxia during pregnancy?
Follow the instructions of your physician.
Resources for hypoxia in pregnancy:
For more information about hypoxia during and after pregnancy, contact http://www.womenshealth.gov/ (800-994-9662 [TDD: 888-220-5446]) or contact the following organizations: