The Heart Pounding Affects of Pregnancy

I was raised an only child by a single mother, this ofcourse means my mother and I are incredibly close. With that being said, the thought of losing her is understandably difficult to imagine and so her story regarding her "brush with death" post my birth always invokes significant fear in me. 

Two days after I was born my mother felt as though she'd been "hit by a truck", so my grandmother drove her to the hospital. She had two different nurses come in and take her blood pressure, both could not believe the readings they were receiving and left my mother for another opinion. On the third trip, her OBGYN came in and took the reading himself. He immediately made her lie down on her left side and said he felt as though he was speaking to a ghost, for her blood pressure was so high he genuinely couldn't believe she was still alive, nonetheless able to walk around and function normally. The reality of this situation is pregnancy-induced hypertension (PIH) affects 7-10% of all pregnancies in the United States (Granger et al, 2001). At a day and age where the question of abortion with regards to the mother's health is still highly controversial, I believe this to be a highly concerning topic. The study specifically looks at the mechanisms for which hypertension occurs in pregnant women and how these abnormal physiological changes occur in contrast to those that occur naturally during pregnancy. As expected, there are numerous physiological changes that occur in women during pregnancy to adapt to and support the embryo being developed. Some of these include: maternal cardiac output and blood volume increases by approximately 40% to 50% (Lindheimer, 1995) and elevations occur in renal plasma flow and glomerular filtration by a rate of approximately 30% to 40% (Hytten, 1974). In women who develop PIH however, these changes do not occur, or they occur at highly abnormal rates. This article mentions the challenges associated with performing mechanistic studies in pregnant women that could provide further answers regarding cause and treatment of PIH, however some potential mechanisms have been suggested in it. A new approach to reducing uteroplacental perfusion conducted on gravid rats after 14 days of gestation suggested arterial pressure could be increased in pregnant hypertensive rats to reflect that of normal pregnancy levels, however this study also indicates that this pregnancy-induced hypertension is associated with proteinuria (elevated protein levels in the urine), reductions in renal plasma flow and glomerular filtration rate, and a hypertensive shift in the pressure natriuresis (excretion of sodium through urine) relationship (Granger et al, 2001). There is also substantial evidence showing NO levels are highly elevated under normal pregnancy conditions, but inhibited in instances of PIH which thus has significant affects on the renal vasodilatation of pregnant women. At this point it appears the mechanism for which PIH occurs in pregnant women remains quite questionable due to the numerous abnormal conditions that appear to occur, however I feel this is very important to understand in the obstetrics field at this point in time. 

Article: Granger JP, Alexander BT, Bennett WA, Khalil RA. Pathophysiology of pregnancy-induced hypertension. In: American Journal of Hypertension [Internet]. Elsevier Inc.; 2001 [cited 2020 Oct 5]. p. 178S-185S.

Available from: https://academic.oup.com/ajh/article/14/S3/178S/205336

References:

Baylis C, Suto T, Conrad K: Importance of nitric oxide in control of systemic and renal hemodynamics during normal pregnancy: studies in the rat and implications for preeclampsia. Hypertens Pregnancy 1996;15:147–169.

Granger JP, Alexander BT, Bennett WA, Khalil RA. Pathophysiology of pregnancy-induced hypertension. In: American Journal of Hypertension [Internet]. Elsevier Inc.; 2001 [cited 2020 Oct 5]. p. 178S-185S.

Khalil RA, Crews JK, Novak J, Kassab S, Granger JP: Enhanced vascular reactivity during inhibition of nitric oxide synthesis in pregnant rats. Hypertension 1998;31:1065–1069.

Lindheimer MD, Katz AI: Renal physiology and disease in pregnancy, in Seldin D.W. and Giebisch G. (Eds). The Kidney: Physiology and Pathophysiology. 2nd ed. Raven Press: New York, 1992. 3371–3431.

Molnar M, Suto T, Toth T, Hertelendy F: Prolonged blockade of nitric oxide synthesis in gravid rats produces sustained hypertension, proteinuria, thrombocytopenia, and intrauterine growth retardation. Am J Obstet Gynecol 1994;170:1458–1466.