Physiological Changes in Pregnancy

Physiological changes occur in pregnancy to nurture the developing fetus and prepare the mother for labor and delivery. Some of these changes influence normal biochemical values while others may mimic symptoms of medical disease. It is important to differentiate between normal physiological changes and disease pathology.

What are Physiological changes?

Pregnancy causes physiologic changes in all maternal organ systems; most return to normal after delivery. These changes happen in response to many factors; hormonal changes, increase in the total blood volume, weight gain, and increase in fetus size as the pregnancy progresses. All these factors have a physiological impact on the pregnant woman: the musculoskeletal, endocrine, reproductive, cardiovascular, respiratory, nervous, urinary, gastrointestinal, and immune systems are affected, along with changes to the skin and breasts. The full gestation period is 39-40 weeks, and pre-term birth is classed as delivery before 37 weeks gestation, although there is variation internationally and it is thought that the length of human pregnancies also varies naturally.

The primary function of pregnancy is to allow for the growth and development of the fetus. All changes that occur within the mother’s body are intended to allow for this growth, as well as for the development of the placenta to nourish the fetus and sustain the pregnancy. 

A pregnant woman will also become hypercoagulable, leading to an increased risk of developing blood clots and embolisms, such as deep vein thrombosis and pulmonary embolism. Women are 4-5 times more likely to develop a clot during pregnancy and in the postpartum period than when they are not pregnant. Hypercoagulability in pregnancy likely evolved to protect women from hemorrhage at the time of miscarriage or childbirth. In third-world countries, the leading cause of maternal death is still hemorrhage. In the United States 2011-2013, hemorrhage made up 11.4% and pulmonary embolisms made up 9.2% of all pregnancy-related deaths.

The increased risk of clots can be attributed to several things. Plasma levels of pro-coagulation factors increased markedly in pregnancy, including von Willebrand Factor, fibrinogen, factor VII, factor VIII, and factor X. Both the production of prostacyclin (an inhibitor of platelet aggregation) and thromboxane (an inducer of platelet aggregation and a vasoconstrictor) are increased, but overall there is an increase in platelet reactivity which can lead to a predisposition to clots. There is also increased blood stasis due to the compression of the vena cava by the enlargening uterus. Many factors have been shown to increase the risk of clots in pregnancy, including baseline thrombophilia, cesarean section, preeclampsia, etc. Clots usually develop in the left leg or the left iliac/ femoral venous system. Recently, there have been several case reports of May-Thurner Syndrome in pregnancy, where the right common iliac artery compresses the below left common iliac vein.

In general, the changes are more dramatic in multifetal than in single pregnancies. These physiologic changes allow the parturient to support the growing uterus and fetus and to withstand labor and the postpartum course. Because the gravida may require surgery while pregnant, it is important to have an appreciation of these physiologic changes. 

Disclaimer

The information, including but not limited to, text, graphics, images and other material contained on this website are for informational purposes only. The purpose of this website is to promote broad consumer understanding and knowledge of various health topics. It is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or another qualified healthcare provider with any questions you may have regarding a medical condition or treatment before undertaking a new health care regimen, and never disregard professional medical advice or delay in seeking it because of something you have read on this website.

Importance of Pulse Oximeter During COVID-19

The whole world is greatly affected by the current COVID-19 pandemic caused due to emerging novel Coronavirus (SARS-CoV-2) which specifically attacks the respiratory system and reduces the oxygen-carrying capacity to develop hypoxia.

Many people with COVID-19 have low levels of oxygen in their blood, even when they feel well. Low oxygen levels can be an early warning sign that medical care is needed. The severely affected COVID-19 patients require ventilators to survive and to fulfill the need for oxygen. However, the number of ventilators is much less than that of the actual number of COVID-19 patients. 

What is a pulse oximeter and what does it measure?

A pulse oximeter is a small non-invasive device that is used to determine hypoxia in patients. The main function of the pulse oximeter is to determine the amount of oxygen saturation (SpO2), which indicates the amount of oxygen in the blood. This can give you valuable information about your health.

Can a pulse oximeter tell if someone has COVID-19?

You may be wondering if an oximeter can help detect COVID-19 early? 

Pulse oximeters are not recommended as a way to tell if someone has COVID-19.  Not everyone who tests positive for COVID-19 will develop low oxygen levels. There are people who may have a very uncomfortable fever, muscle aches, and GI upset at home, but never demonstrate low oxygen levels. Get tested if you have signs of COVID-19 or if you have been in close contact with someone who has it. The pulse oximeter can be used in primary clinical care to determine oxygen saturation. Furthermore, pulse oximeters have become a game-changer in the COVID-19 pandemic to detect the oxygen requirement in patients. However, there are several factors affecting the sensitivity of pulse oximeters that need to be understood to get an accurate reading. 

Can a pulse oximeter be a helpful tool for monitoring COVID-19 at home?

An oximeter can be a helpful tool for monitoring oxygen levels so that low oxygen levels can be detected early if a person has a mild case of COVID-19 and is self-treating at home. If you have tested positive for COVID-19 and are concerned about any developing symptoms, check immediately with your healthcare provider. If you are experiencing severe chest pain, uncontrollable coughing, or dusky lips or fingers, it’s time to go to the ER.

The pulse oximeter gives only primary judgment about oxygen saturation and it is not at all a substitute for the ABG analysis. Moreover, the pulse oximeter cannot be relied on as a sole monitor to check the various events such as cardiac complications/arrests, respiratory tract-related problems, oesophageal intubation, or failure of oxygen supply.

Disclaimer

The information, including but not limited to, text, graphics, images and other material contained on this website are for informational purposes only. The purpose of this website is to promote broad consumer understanding and knowledge of various health topics. It is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or another qualified healthcare provider with any questions you may have regarding a medical condition or treatment and before undertaking a new health care regimen, and never disregard professional medical advice or delay in seeking it because of something you have read on this website.

References:

https://www.tandfonline.com/doi/full/10.1080/00194506.2020.1845988

https://www.houstonmethodist.org/blog/articles/2020/aug/can-an-oximeter-help-detect-covid-19-at-home/

https://www.health.state.mn.us/diseases/coronavirus/pulseoximeter.html