Chapter 007. Medical Disorders during Pregnancy (Part 1)

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Harrison's Internal Medicine Part 1. Introduction to Clinical Medicine Chapter 7. Medical Disorders during Pregnancy Medical Disorders during Pregnancy: Introduction Approximately 4 million births occur in the United States each year. A significant proportion of these are complicated by one or more medical disorders. Three decades ago, many medical disorders were contraindications to pregnancy. Advances in obstetrics, neonatology, obstetric anesthesiology, and medicine have increased the expectation that pregnancy will result in an excellent outcome for both mother and fetus despite most of these conditions. Successful pregnancy requires important physiologic adaptations, such as a marked increase in cardiac output. ...

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Chapter 007. Medical Disorders during Pregnancy (Part 1) Harrison's Internal Medicine > Part 1. Introduction to Clinical Medicine > Chapter 7. Medical Disorders during Pregnancy Medical Disorders during Pregnancy: Introduction Approximately 4 million births occur in the United States each year. A significant proportion of these are complicated by one or more medical disorders. Three decades ago, many medical disorders were contraindications to pregnancy. Advances in obstetrics, neonatology, obstetric anesthesiology, and medicine have increased the expectation that pregnancy will result in an excellent outcome for both mother and fetus despite most of these conditions.
Successful pregnancy requires important physiologic adaptations, such as a marked increase in cardiac output. Medical problems that interfere with the physiologic adaptations of pregnancy increase the risk for poor pregnancy outcome; conversely, in some instances pregnancy may adversely impact an underlying medical disorder. Hypertension (See also Chap. 241) In pregnancy, cardiac output increases by 40%, most of which is due to an increase in stroke volume. Heart rate increases by ~10 beats/min during the third trimester. In the second trimester of pregnancy, systemic vascular resistance decreases and this is associated with a fall in blood pressure. During pregnancy, a blood pressure of 140/90 mmHg is considered to be abnormally elevated and is associated with an increase in perinatal morbidity and mortality. In all pregnant women, the measurement of blood pressure should be performed in the sitting position, because for many the lateral recumbent position is associated with a blood pressure lower than that recorded in the sitting position.
The diagnosis of hypertension requires the measurement of two elevated blood pressures, at least 6 h apart. Hypertension during pregnancy is usually caused by preeclampsia, chronic hypertension, gestational hypertension, or renal disease. Preeclampsia Approximately 5–7% of all pregnant women develop preeclampsia , the new onset of hypertension (blood pressure >140/90 mmHg) and proteinuria (>300 mg/24 h) after 20 weeks of gestation. Although the precise placental factors that cause preeclampsia are unknown, the end result is vasospasm and endothelial injury in multiple organs. Excessive placental secretion of a soluble fms-like tyrosine kinase 1, a naturally occurring vascular endothelial growth factor antagonist, and decreased secretion of placental growth factor may contribute to the endothelial dysfunction, hypertension, and proteinuria observed in preeclampsia. Glomerular endothelial cells demonstrate swelling and encroach on the vascular lumen. Preeclampsia is associated with abnormalities of cerebral
circulatory autoregulation, which increase the risk of stroke at near-normal blood pressures. Risk factors for the development of preeclampsia include nulliparity, diabetes mellitus, a history of renal disease or chronic hypertension, a prior history of preeclampsia, extremes of maternal age (>35 years or 160/110 mmHg), severe proteinuria (>5 g/24 h), oliguria or renal failure, pulmonary edema, hepatocellular injury (ALT > 2 x the upper limits of normal), thrombocytopenia (platelet count < 100,000/L), or disseminated intravascular coagulation. Women with mild preeclampsia are those with the diagnosis of new-onset hypertension, proteinuria, and edema without evidence of severe preeclampsia. The HELLP (hemolysis, elevated liver enzymes, low platelets) syndrome is a special subgroup of severe preeclampsia and is a major cause of morbidity and mortality in this disease. The presence of platelet dysfunction and coagulation disorders further increases the risk of stroke.