Wednesday, April 25, 2012

Obsetry and Gynecology : Maternal Physiology

 

Maternal physiology undergoes many changes during pregnancy. These changes, which are largely secondary to the effects of progesterone and estrogen, begin as early as 4 week gestation and are progressive. In the First 12 weeks of pregnancy progesterone and estrogen are produced predominantly by the ovary and thereafter by placenta. These change both enable the fetus and placenta to grow and prepare the mother and baby for childbirth. These condition will makes a physiologic adaptations in the mother body system, such as hematology system, cardiovascular system, respiratory system, endocrine system and the others.

CARIOVASCULAR SYSTEM

Estrogen and progesterone mediated relaxation of vascular smooth muscle in pregnancy cause vasodilatation reducing the peripheral vascular resistance by 20%. consequently systolic and diastolic blood fall (figure1.1). A reflex increase in heart rate by 25% together with a 25% cardiac output (figure 1.2). Activating of renin-angiotensin system result in increased circulating angiotensin II which encourages sodium and water retention (leading to a 40% increase in blood volume) and directly constricts the peripheral