About one million persons in the United States have congenital cardiovascular disease, and each year an estimated 32,000 babies, about 8 per 1000 live births, are born with this disease.2,43 Of the new cases, 8 to 13 percent have atrial sepal defects, 6 to 11 percent have patent ductus arteriosus, and 20 to 25 percent have ventricular sepal defects. The prevalence of congenital heart disease at birth as determined during the infant's brief stay in the hospital is likely to be underestimated, and recognition of specific lesions may be inaccurate.44 Most data are deficient for a diagnosis after the first week of life. Prevalence data based on autopsy findings are unreliable because they reflect a fraction of the deaths and relate only to fatal lesions. Most information comes from retrospective studies based extensively on referral practices.
Structural abnormalities of the heart or intrathoracic great vessels seem to affect 8 to 10 of every 1000 infants born alive in the United States. If bicuspid aortic valves and mitral valve prolapse manifested later in life are included, the rate may well exceed 1 percent of live births. About 1 newborn per 1000 live births has a cardiac birth defect that cannot be managed medically or surgically. Most infants who previously would have died now survive to adult life because of improved treatment, but 5 to 6 of these infants per 1000 live births require frequent medical or surgical attention shortly after birth or later in childhood.
Except for the recent unexplained twofold increase in ventricular sepal defects and the threefold increase in patent ductus arteriosus, the incidence of most congenital heart diseases has remained stable. Rubella vaccine has reduced rubella-caused congenital heart disease, and congenital heart defects associated with Down's syndrome are less common because older women are having fewer babies. Pregnancies may be terminated if prenatal screening reveals Down's syndrome. Preventive strategies are impeded by lack of knowledge of the cause of most congenital heart disease, although it is known that alcohol, trimethadione, and lithium can cause cardiac defects. The majority of congenital heart disease may involve complex genetic-environmental interactions that remain to be elucidated (see Chaps. 69 and 70).
About 75 of each 1000 live births in the United States are premature, with the infants weighing less than 2500 g.i2 Almost half of premature infants weighing less than 1750 g will maintain patency of their ductus arteriosus, possibly because their immature lungs do not properly metabolize prostaglandins that cause the ductus to remain open.45 The growing number of teratogens identified appears to account for only 5 percent of all human malformations, and single mutant genes are said to be responsible for only 3 percent of cases.
In 1997, deaths in infancy from congenital cardiovascular disease occurred at the rate of 0.5 per 1000 live births, about one-half the rate that occurred in 1980.8 The 1-year fatality rate among the estimated 32,000 new cases at birth each year was about 6.5 percent in 1997. About 25 percent of infants with congenital heart disease have a malformation incompatible with life beyond the first year; possibly half of these can be treated surgically to improve the quality of life, if not to produce a cure. About 2.5 per 1000 live-born infants require specialized services for diagnosis and treatment of congenital heart disease shortly after birth, and another 2.5 per 1000 will need these resources later in childhood.
With the exception of bicuspid aortic valve in older patients, ventricular septal defect is the most common variety, accounting for 30 percent of congenital heart disease. Some 75 percent of congenital heart disease in infants and children is encompassed by seven defects: ventricular sepal defect, pulmonary stenosis, patent ductus arteriosus, tetralogy of Fallot, aortic stenosis, coarctation of the aorta, and transposition of the great arteries. There is an excess of birth defects in blacks. The rate among siblings is 17 per 1000 compared with 2.6 per 1000 in the general population (see Chap. 70).
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The first trimester is very important for the mother and the baby. For most women it is common to find out about their pregnancy after they have missed their menstrual cycle. Since, not all women note their menstrual cycle and dates of intercourse, it may cause slight confusion about the exact date of conception. That is why most women find out that they are pregnant only after one month of pregnancy.