Frequently, a fetal genetic abnormality is discovered when the family history leads a fetal medicine specialist to attempt prenatal diagnosis by the identification of particular fetal features or performance of a test requiring an invasive procedure. But the reverse scenario also is possible, in which recognition of disease in the fetus results in the same diagnosis being made in a parent with few or no symptoms, or in relatives who were previously unaware of the problem. An example is the finding of hyperechogenic kidneys in a mid-trimester fetus, which prompts scanning of the parents’ kidneys to detect polycystic kidney disease. The authors report 20 such families, seen in the years 1999–2004, in which recognition of a fetal anomaly led to the diagnosis of an asymptomatic parent.
In each instance, ultrasound studies demonstrated one or more structural fetal abnormalities. Anomalies found in more than one fetus included cleft lip and palate, cardiac anomalies, nuchal anomalies, micromelia, polydactyly, and bilateral club foot associated with polyhydramnios, akinesia, or camptodactyly. The mean gestational age when the fetal anomaly was diagnosed was 21.2 weeks, and at the time of genetic counseling, 23.4 weeks. Genetic counseling helped to diagnose nine maternal diseases, the commonest being myotonic dystrophy. Eleven paternal diseases were found; the only one diagnosed more than once was osteogenesis imperfecta. In no case did the parents know that they might transmit a genetic disease to their children. None of the couples were consanguineous.
In all cases, a family history and clinical examination led to precise diagnosis of the fetal anomaly and disclosed the familial origin of the genetic disease. Twelve individuals had, at the most, minor clinical symptoms. Six had had a defect repaired in infancy and were doing well. Four others had unspecified disease that had not been investigated. Thirteen couples chose to continue the pregnancy; there was one intrauterine fetal death and one preterm birth. The other seven couples wished to terminate the pregnancy because they faced the possibility of the fetus having a more severe form of the disease. Without exception, the diagnosis suspected before birth was confirmed afterward.
Prenatal diagnosis of a fetal anomaly may be the first clue that a familial disorder may be present, and can disclose familial disease that has not previously been recognized in one of the parents. Future pregnancies as well as the current gestation should be considered when the parents are counseled and a decision is made regarding whether to continue or end the pregnancy.