Medical brain notes 42

  PRECONCEPTION CARE   Preconception care includes the identification of those conditions that could affect a future pregnancy or fetus and that may be amenable to intervention.  Adverse effects on the fetus,including spontaneous abortion or congenital anomalies caused by medications or poorly controlled diabetes melli-tus, can be reduced with proper care prior to pregnancy. Preconception care can be provided at any healthcare en-counter during a woman’s reproductive years. 

  Anemia   The plasma and cellular composition of blood change sig-nificantly during pregnancy, with the expansion of plasma volume proportionally greater than that of the red blood cell mass. On average, there is a 1000-mL increase in plasma volume and a 300-mL increase in red-cell volume (a 3:1 ratio). Because the hematocrit (Hct) reflects the pro-portion of blood made up primarily of red blood cells, Hct demonstrates a “physiologic” decrease during pregnancy; therefore, this decrease is not actually an anemia.   Anemia in pregnancy is generally defined as an Hct less than 30% or a hemoglobin of less than 10 g/dL.   The direct fetal consequences of anemia are minimal, although infants born to mothers with iron deficiency may have diminished iron stores as neonates. The maternal consequences of anemia are those associated with any adult anemia. If anemia is corrected, the woman with an ade-quate red-cell mass enters labor and delivery better able to respond to acute...

  Anemia   The plasma and cellular composition of blood change sig-nificantly during pregnancy, with the expansion of plasma volume proportionally greater than that of the red blood cell mass. On average, there is a 1000-mL increase in plasma volume and a 300-mL increase in red-cell volume (a 3:1 ratio). Because the hematocrit (Hct) reflects the pro-portion of blood made up primarily of red blood cells, Hct demonstrates a “physiologic” decrease during pregnancy; therefore, this decrease is not actually an anemia.   Anemia in pregnancy is generally defined as an Hct less than 30% or a hemoglobin of less than 10 g/dL.   The direct fetal consequences of anemia are minimal, although infants born to mothers with iron deficiency may have diminished iron stores as neonates. The maternal consequences of anemia are those associated with any adult anemia. If anemia is corrected, the woman with an ade-quate red-cell mass enters labor and delivery better able to respond to acute...

  The Hemoglobinopathies   More than 270 million people worldwide are heterozygous carriers of hereditary disorders of hemoglobin, and at least 300,000 affected homozygotes or compound homozygotes are born each year. The hemoglobinopathies include the thalassemias ( α -thalassemia,  β -thalassemia) and the sickle cell spectrum: sickle cell trait (Hb AS), sickle cell disease (Hb SS), and sickle cell disorders (Hb SC and sickle cell  β -thalassemia) (Table 14.1).   Hemoglobin (Hb) consists of four interlocking poly-peptide chains, each of which has an attached heme mol-ecule. The polypeptide chains are called alpha, beta, gamma, delta, epsilon, and zeta. Adult hemoglobins con-sists of two alpha chains and either two beta chains (Hb A), two gamma chains (Hb F), or two delta chains (Hb A 2 ). The beta chains are the oxygen-carrying subunits of the hemoglobin molecule. Hb F is the primary hemoglobin of the fetus from 12 to 24 weeks of gestation. In the third trimeste...

  DIABETES MELLITUS   Approximately 2% of pregnancies are complicated by dia-betes that either develops during pregnancy (gestational diabetes) or was antecedent to pregnancy (pregestational diabetes mellitus).  In either case, diabetes has significant impli-cations for mother and fetus during pregnancy, and, conversely, pregnancy significantly affects diabetes.  Whether diabetes isnewly diagnosed or long-standing, intense management may be stressful, and all those involved with obstetric care should be mindful of the extra emotional attention many of these patients need.   Classification of Diabetes in Pregnancy   The American Diabetes Association (ADA) identifies three forms of glucose intolerance:   Type 1 diabetes mellitus  refers to diabetes diagnosedin childhood. It is thought to be caused by immunologic destruction of cells of the pancreas, resulting in necessary  insulin  replacement.  Diabetic ketoacidosis (DKA)  ismor...

  Physiology of Glucose Metabolism in Pregnancy   Dietary habits frequently change during pregnancy. Food intake may decrease early in pregnancy because of nausea and vomiting, and food preferences may change later in pregnancy. Several pregnancy-associated hormones also have a major effect on glucose metabolism. Most notable of these is  human placental lactogen (hPL),  which is produced in abundance by the enlarging placenta. HPL affects both fatty acid and glucose metabolism. It promotes lipolysis with increased levels of circulating free fatty acids and causes a decrease in glucose uptake. In this manner, hPL can be thought of as an anti-insulin. The increasing production of this hormone as pregnancy advances gener-ally requires ongoing changes in insulin therapy to adjust for this effect.   Other hormones that have demonstrated lesser effects include  estrogen  and  progesterone,  which interfere with the insulin-glucose relation; and...

  Fetal Morbidity and Mortality in Pregestational and Gestational Diabetes   Infants of mothers with diabetes are at a six-fold increased risk of congenital anomalies over the 1% to 2% baseline risk of all patients.  The most commonly encountered anomalies arecardiac and limb deformities.  Sacral agenesis  is a unique but rare anomaly for this group (Fig. 14.2).   The risk of  spontaneous abortion  is similar in patients with well-controlled diabetes and in patients without dia-betes, but the risk is significantly increased for the patients  with diabetes if glucose control is poor.     There is also an in-creased risk of intrauterine fetal demise and stillbirth, especially when diabetic control is inadequate.  Because of this potentiallydevastating outcome, beginning at approximately 30 to 32 weeks of gestation, various antepartum fetal tests may be initiated to monitor fetal health (see “Antepartum Fetal Monitoring” sections ...

  Pregestational Diabetes Approximately 1% of all pregnant patients are diabetic before pregnancy. Type 2 pregestational diabetes mellitus is most common.  Although 90% of diabetes cases encounteredduring pregnancy are GDM, more than one half of these even-tually develop type 2 pregestational diabetes mellitus later in life.   ANTEPARTUM FETAL MONITORING   Women with pregestational diabetes should receive an ultrasound examination early in pregnancy to check for fetal viability and accurately date the gestational age. At 18 to 20 weeks of gestation, an ultrasound examination that focuses on identification of congenital anomalies, es-pecially those of the heart and great vessels, is indicated. Echocardiography may also be done if there are suspected cardiac defects or when the fetal heart and great vessels could not be visualized by ultrasonography.   Antepartum fetal monitoring, including fetal movement counting, the nonstress test, biophysical profile, and cont...