The care of the child begins with the care of the fetus. Accurate prenatal diagnosis and optimal perinatal management strongly affect the outcomes of the future infant, not just in childhood but throughout life. Careful planning of perinatal care for high risk pregnancies improves neonatal outcomes. Optimal maternal and fetal care with high-risk pregnancies improves neonatal outcomes and also decreases mortality and morbidity of mothers. Over the last 3 decades, fetal medicine has evolved into a distinct discipline that primarily focuses on the fetus as a patient. Many hospitals now have fetal medicine programs with coordinated and integrated care provided by subspecialists and support staff from maternal-fetal medicine and pediatric subspecialties such as neonatology, surgery, neurosurgery, urology, cardiology, genetics, palliative care, and ethics. This chapter will provide a brief overview of assessment of fetal well-being, prenatal screening and diagnostic tests, common problems that affect the fetus (including disorders of fetal growth, fetal anomalies, prematurity, and multiple pregnancies), and fetal therapy.
FETAL GESTATION AND GROWTH
The accurate assessment of gestational age and fetal growth are essential for care of the fetus. The assignment of gestational age is more accurate in early gestation and decreases with advancing gestation. The standard method to assign fetal gestation uses the last menstrual period (LMP), often with confirmation using ultrasonographic measurement of the crown–rump length in the first trimester or biparietal diameter, head circumference, abdominal circumference, and femur length in the second trimester. Serial biometric measurements can be used in combination to evaluate fetal growth.
Although fetal biometric measurement is the gold standard method of estimating fetal gestational age and assessing fetal growth, there can be some differences when assessing fetal patients with different ethnic backgrounds. According to studies conducted at the National Institutes of Health, current ultrasonographic standards for evaluating fetal growth may result in up to 15% of fetuses to be misclassified as small for gestational age (SGA). Prenatal growth charts were first derived from ultrasound measurements of 139 predominantly middle-class white pregnant women during the 1980s. Currently, many population-based studies are being conducted to develop more accurate ultrasonographic fetal growth standards. Of these, the most prominent one is the Intergrowth-21st project.
Fetal growth assessment detects abnormalities of growth that are associated with fetal and neonatal morbidity and mortality. As in children, fetal growth is assessed by the percentile of the estimated fetal weight (EFW) at a particular gestational age. Fetuses whose weight is on percentile curves below the tenth percentile are considered SGA, and those above the 90th percentile are considered large for gestational age (LGA). The cutoff at the tenth percentile is arbitrary, and some fetuses who are SGA do not have any identifiable disease. They may simply be constitutionally small, with their small size attributable to factors such as maternal ethnicity, parity, and body mass. However, some fetuses may have pathologic conditions leading to attenuation of growth, and are said ...