Alternate methods of first-trimester diagnosis.

Fetal medicine is a new discipline that emerged out of the expansion of modern technology. Evaluation of the fetus heretofore was not possible except by indirect methods. Pregnancy management focused primarily on the care of the mother with the expectation that the fetus would be an indirect beneficiary. Our present-day approach to pregnancy and prenatal evaluation has been altered by the introduction of new techniques such as ultrasound, amniocentesis, and CVS, which have made the fetus and its intrauterine environment accessible. Improvements in ultrasonographic equipment have allowed for better visualization of the fetus, earlier detection of structural anomalies, and facilitation of the performance of invasive procedures. The recent introduction of CVS represents a major step toward achieving the goal of early diagnosis. Prevailing experience has demonstrated that it is a relatively safe and reliable procedure with a low complication rate. Early amniocentesis may be considered as an alternative to CVS when the latter is not advisable, although future studies are needed to accurately estimate the procedure-related risks (Table 5). Transcervical endoscopy allows a more detailed appreciation of fetal anatomy, although its role in clinical practice remains to be defined. Biochemical markers such as alpha fetoprotein, unconjugated estriol, and hCG, alone and in combination, have been studied regarding their potential to predict chromosomal abnormalities. Today there is a changing trend in prenatal diagnosis with women requesting more information about their unborn child and expecting such information earlier in gestation. The goal of prenatal diagnosis has been directed toward earlier detection to reduce the anxiety of waiting and permit the safer option of first-trimester termination of pregnancy.