A mother who is pregnant undergoes multiple physiological and anatomical changes that are vital in nurturing and accommodation of fetus (Soma-Pillay et al., 2016). These changes start immediately after conception and impact all the vitals organ system in the body of a woman. For multiple women who have normal pregnancy, these changes resolve after pregnancy with no residual impacts (Soma-Pillay et al., 2016). Comprehending the physiological changes that occur in pregnancy is vital in differentiating abnormal adaptations.
Increase of Plasma Volume
One of the most important physiological changes that occurs during pregnancy is the progressive increase of plasma volume. Vricella (2017) explains that plasma volume expansion is a well-researched aspect of pregnancy physiology that is imperative in successful outcomes of pregnancy. Plasma volume increase is important in the expansion of total blood volume in pregnant women. It starts as early as the 6th week of gestation and peaks around the 32nd week and plateaus until a mother delivers. The expansion of plasma volume is achieved by an increase in water reabsorption and sodium at the kidney level (Vricella, 2017). Also, the increase of cardiac output, the systemic blood pressure, and decreased systemic vascular resistance also facilitates plasma volume expansion. The plasma volume expansion is important because it supports normal growth. Besides, it is important for the proper development of the fetus and prevents hemorrhage during delivery time. Vricella (2017) explains that some diseases such as lupus nephritis, pre-eclampsia, and advanced diabetes can result to insufficient expansion of plasma volume.
Cardiac alterations are another significant physiological change that happens during pregnancy. The alterations in the cardiovascular system are significant and begin early in pregnancy, with cardiac output increasing by 20% by the eighth week of pregnancy (Soma-Pillay et al., 2016). Peripheral vasodilation is the most significant heart alteration that occurs during pregnancy. Endothelium-facets regulate peripheral vasodilation, including nitric oxide generation, which is stimulated by two main hormones, oestradiol and vasodilatory prostaglandins (PG12). Systemic vascular resistance falls by around 27% as a result of peripheral vasodilation, while cardiac output increases by about 40% to compensate for this during pregnancy (Soma-Pillay et al., 2016). The increase in cardiac output is mostly done by increasing stroke volume, and to a lesser extent by increasing heart rate. The fetus has to be fed, hence changes in cardiac output are vital.
Alteration of the Alimentary Canal
Another significant physiological change that happens during pregnancy is the alteration of the alimentary tract. Approximately 50-90 percent of women experience nausea and vomiting during pregnancy (Soma-Pillay et al., 2016). This could be a pregnancy-related adaptation mechanism aimed at avoiding a pregnant woman from consuming possibly teratogenic items like veggies and strong-tasting foods (Soma-Pillay et al., 2016). Although the actual process causing the shift in the alimentary canal is unknown, several study materials have shown that pregnancy-related hormones such as progesterone, estrogen, and human chorionic gonadotropin (hCG) may be involved. Thyroid hormones play a role in the development of nausea symptoms. Thyroid stimulating hormones and human chorionic gonadotropin have similar biomolecular structures, resulting in cross-reaction. The thyroid gland is stimulated by the cross reaction, resulting in nausea. The nausea feeling usually disappears by the 20th week in most pregnancies, however about 10% of pregnant women suffer nausea symptoms beyond the 20th week and until the end of the gestation period (Soma-Pillay et al., 2016).
The physiological changes that occur in pregnancy are vital in ensuring the pregnancy is successful. Various physiological changes such as changes in cardiac output, plasma volume, and alimentary tract occur. Understanding these changes ensure is vital in identifying abnormal pregnancies.
Soma-Pillay, P., Nelson-Piercy, C., Tolppanen, H., & Mebazaa, A. (2016). Physiological changes in pregnancy. Cardiovascular Journal of Africa, 27(2), 89–94. https://doi.org/10.5830/cvja-2016-021
Vricella, L. K. (2017). Emerging understanding and measurement of plasma volume expansion in pregnancy. The American Journal of Clinical Nutrition, 106(Supplement 6), 1620S1625S. https://doi.org/10.3945/ajcn.117.155903