CHANGES DURING PREGNANCY

Updated: Jan 26

During pregnancy, the maternal organism changes, not only externally, but also in the anatomy and function of certain tissues, organs and systems, in order to ensure the well-being of the mother and her baby; during this period the mother must house the baby and nourish it during its development. Physiological changes may be reflected in the levels of certain laboratory parameters and others may even mimic symptoms of a disease (1).

Pregnancy involves changes in the anatomy and function of the maternal organism in order to meet the needs of both.

The complex interaction between anatomical changes and changes in the function of the maternal organism can be observed by the effect of the volume of the fetus during its growth; as the placenta develops and the uterus enlarges, they will receive a greater proportion of blood flow; then organs such as the kidneys will receive more blood to filter the wastes of both the fetus and the mother, all of these changes are propitiated by the endocrine system (2).

The main changes include the following systems and apparatuses:

Endocrine: There is a hormonal readjustment in the maternal organism in order to coordinate the adjustments that it must carry out.

Cardiovascular: Increases the amount of blood pumped by the heart to ensure proper distribution of molecules and nutrients carried in the blood.

Respiratory: Given the increased function of multiple organs, oxygen consumption and metabolism also increase, therefore ventilation must be increased.

Blood: Increases the amount of blood in the mother's body, to ensure an adequate supply for both the baby and the mother, in addition to preparing her for childbirth.

Renal: Certain filtration parameters change in order to correspond to the new demands of the organism, for example, due to an increase in circulating volume.

Gastrointestinal: There is a rearrangement of the organs in the abdomen due to the growth of the uterus.

Some discomforts of pregnancy, such as nausea and vomiting, are common and are due to maternal changes.

Physiological changes can frequently cause gastrointestinal discomfort, such as heartburn, nausea and vomiting or constipation; most of these are mild to moderate and are mostly a consequence of hormonal changes: progesterone contributes to delay gastric emptying and gastrin increases gastric acidity (3).

Nausea and vomiting are the most common medical conditions during pregnancy and affect most pregnant women from the 4th to the 6th week, peaking between the 8th and 12th week and often ceasing by the 20th week. The exact mechanism is not fully understood, but it is believed to be due to endocrine and psychological factors (1). Most women do not require medication and can be treated with alternative options and dietary modifications (split meals, avoidance of fatty foods and fresh vegetables which may delay gastric emptying) (3).

Constipation usually occurs in the first and second trimester. The mechanism seems to be mostly related to endocrine changes (progesterone causes intestinal hypomotility), in addition, pregnant women have a greater absorption of water in the colon (due to higher levels of aldosterone). Adequate water intake and a diet rich in fiber are recommended; split meals may be an alternative (3).

References

Soma-Pillay P, Nelson-Piercy C, Tolppanen H, Mebazaa A. Physiological changes in pregnancy. Cardiovasc J Afr. 2016;27(2):89-94. doi:10.5830/CVJA-2016-021

Kepley JM, Bates K, Mohiuddin SS. Physiology, Maternal Changes. [Updated 2020 Mar 30]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available from: https://www.ncbi.nlm.nih.gov/

Gomes CF, Sousa M, Lourenço I, Martins D, Torres J. Gastrointestinal diseases during pregnancy: what does the gastroenterologist need to know?. Ann Gastroenterol. 2018;31(4):385-394. doi:10.20524/aog.2018.0264

CHANGES DURING PREGNANCY

References

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