American Academy of Pediatrics, American College of Obstetricians and Gynecologists (2007). Antepartum care. In Guidelines for Perinatal Care, 6th ed., pp. 83-137. Elk Grove Village, IL: American Academy of Pediatrics.
Cunningham FG, et al. (2010). Prenatal diagnosis and fetal therapy. In Williams Obstetrics, 23rd ed., pp. 287-311. New York: McGraw-Hill Medical.