Case 1: An ultrasound performed at 20 weeks' gestation in your 21-year-old G2 P1 patient indicates an apparently isolated unilateral cleft lip/cleft palate in the fetus (Figure 10-1).
Three-dimensional ultrasound rendering of a fetus with a left cleft lip.
The purpose of this chapter is not to provide an in-depth discussion of particular fetal malformations, nor to cover a comprehensive list of fetal malformations. Rather our purpose is to discuss the genetic implications of common ultrasound-detected fetal malformations, and outline the general principles for evaluating and managing fetal structural abnormalities.
Cleft lip with, or without, cleft palate is one of the most common birth defects in the United States, occurring in approximately 1 in 1000 live births annually.1 Most cases of clefting appear multifactorial; that is, a combination of genetic determinants and environmental factors. Certain medications, such as anticonvulsants, are associated with an increased risk for cleft lip/cleft palate. Likewise, poorly controlled diabetes in pregnancy can increase the risk of fetal clefts. Most importantly, a significant number of clefts, especially cleft palate, are part of a genetic syndrome, and the prognosis for the child will depend on the underlying condition, and not the severity of the cleft.
Initial evaluations should be aimed at determining if the cleft is an isolated finding.2 Amniocentesis should be performed for standard chromosome testing and microarray testing. A fetal echocardiogram should be done to exclude cardiac malformations that would suggest a genetic syndrome. Equally important is a complete family history to determine if other family members are known to have facial clefts, or other birth defects. Counseling of the patient regarding prognosis for her child should be done by a multidisciplinary team with experience in managing infants and children with craniofacial abnormalities.
Case 2: Your 34-year-old infertility patient who conceived by ovulation induction has just had a first-trimester ultrasound indicating “fetal exencephaly.” How do you counsel the patient regarding prognosis, management, and risk of recurrence in future pregnancies?
Neural tube defects (NTD) are common birth defects occurring in 1 to 2 per 1000 live births. Included in the category of NTD are anencephaly, myelomeningocele, and encephalocele. Most are characterized by multifactorial inheritance, with the one known environment factor being maternal folic acid intake. With most pregnancies now being screened by maternal serum alpha-fetoprotein (MSAFP) and/or a second trimester ultrasound, most cases of NTD are being detected in utero. Once the ultrasound diagnosis of a specific NTD is made, an appropriate genetic work-up should be done to provide both prognostic and recurrence risk information to the couple.
Anencephaly is characterized by a complete absence of skull development, and after the second trimester of pregnancy, absence of the cerebral hemispheres. However, on first trimester ultrasounds, fetal brain can be ...