Increasingly, genomic analysis is being utilized to diagnose children with developmental delay or dysmorphic facial features suggestive of a congenital disorder. Genetic testing has rapidly evolved, and the genome-wide tests that we use today are significantly different from the more targeted single-gene tests of the last decade. Chromosomal microarray analysis (CMA) is now a first line test for children with multiple birth defects, children with intellectual impairment (including autism), and children with an unusual constellation of symptoms that do not fit with a known disease.1 There are three types of CMA that are currently clinically available. CMA by oligonucleotide array-based comparative genomic hybridization (aCGH) compares the hybridization signal from the patient’s DNA to that of a reference DNA sample for each oligonucleotide on the array. Depending on the specific array, this can range from tens of thousands to hundreds of thousands of oligonucleotides. A relative loss of signal from the patient’s DNA is interpreted as a deletion, whereas a relative gain is interpreted as a duplication (or, in rare cases, a triplication or quadruplication). aCGH can detect very small losses or gains of DNA and typically uncovers genetic abnormalities in about 10–20% of cases.2 CMA by single nucleotide polymorphism (SNP) analysis uses a completely different technology to genotype the individual at hundreds of thousands to millions of single nucleotides that are commonly polymorphic in the genome. Gains and losses of DNA are detected by relative increases or decreases of the signal at each SNP relative to the other SNPs on the array, as well as by the specific genotypes seen at SNPs that are located in tandem in the genome.3 Like aCGH, SNP analysis will detect losses or gains of DNA, but it will sometimes miss very small changes that aCGH can detect. However, SNP analysis, unlike aCGH, can also detect areas where chromosome pairs or parts of the chromosome pairs are identical to one another. Most recently, hybrid arrays have been developed that combine both technologies into a single test. Since one copy of each pair of chromosomes is inherited from the mother and the other pair of each chromosome is inherited from the father, when parts of chromosome pairs are identical (i.e., there is an absence of heterozygosity (AOH)), there are two possibilities. If only one chromosome is involved, then the cause could either be uniparental isodisomy (meaning the child inherited two identical copies of a chromosome from one parent and no copy of the same chromosome from the other parent), or distant consanguinity (meaning the parents are distant blood relatives).4 If multiple chromosomes are involved, then the parents must be blood relatives of one another. The closeness of the relationship between the parents can be estimated based on the number and size of the chromosome blocks that are identical. Analysis of parental samples is not required to make this determination, but it can confirm the finding and can conclusively identify the father of the child. In February 2011, our colleagues at Baylor College of Medicine (BCM) reported several children with intellectual or developmental disability or with multiple congenital abnormalities who were referred for genetic testing and in whom SNP analysis revealed large regions of AOH on multiple chromosomes.5 Since that publication, clinicians at BCM have seen a total of seven children in whom SNP-analysis revealed large regions with AOH accounting for between 19–25% of the genome, which is consistent with a finding that the child was conceived by first-degree relatives (i.e., parent-child or full siblings) (Table 1). The children ranged in age from newborn to 11 years old. None of the mothers were themselves under the age of 18 at the time of testing, but at least four were minors when the child was conceived. In only 2 of the 7 cases was consanguinity suspected prior to testing. As is common practice in many states, testing was performed without the requirement for specific informed consent, so the possibility of identifying AOH was typically not addressed prior to receiving the results, unless consanguinity was already suspected. In all of these cases, questions were raised about whether the physicians had an obligation to report the findings to Child Protective Services (CPS) or whether doing so would be an unethical breach of patient confidentiality. Table 1 Cases of First-Degree Consanguinity Identified through SNP Analysis Informed Consent for Genetic Testing The U.S. does not have a uniform federal policy requiring specific informed consent for clinical genetic testing. Requirements for obtaining legally adequate informed consent are generally determined by state law. The majority (n=37) of states, including Texas, do not require specific informed consent to order a genetic test6 because it is considered a routine diagnostic test that is authorized under the general consent to treat that patients sign upon admission to a hospital or clinic. Out of the thirteen states that do require specific informed consent for genetic testing, inconsistencies exist as to what information should be disclosed.7 Six states only require that the patient sign a written informed consent document prior to testing. The remaining seven states expressly list what information the informed consent document must include.8 These states typically require that, at a minimum, the consent form explain the purpose of the test, the intended use of the genetic information derived, and a description of what conditions will be tested for.9 Not surprisingly, no state specifically addresses the possibility of identifying cases of AOH or that it could lead to suspicion of child abuse if the mother is a minor, triggering state mandated reporting requirements. With the emergence of new genetic technologies, like CMA, it is increasingly common for genetic tests to reveal clinically relevant incidental findings, as well as unanticipated variants of uncertain significance not directly related to the patient’s phenotype. In some cases, parents may choose not to receive this information, especially if it is not immediately clinically actionable. There is much debate about how much authority parents should have to make these decisions on behalf of their minor children.10 In all cases, however, parents have the right to refuse genetic testing for their child, unless doing so would result in serious harm or imminent death. In order to make this decision, it is important that parents are adequately informed of the risks and benefits of genetic testing, including the potential to identify unanticipated findings (like AOH) and variants of uncertain significance. However, it does not necessarily follow that the possibility of discovering information that could lead to a suspicion of child abuse should also be disclosed. For most patients, this information will be irrelevant but could cause unnecessary anxiety and could even lead to the refusal of an important diagnostic test. Further, there are many clinical tests that are performed that have the potential to reveal findings that could lead to suspicion of abuse. Consider, for example, chest X-rays performed on children who present to the emergency department with respiratory issues. Parents are not typically informed that the results of the x-ray may lead to suspicion of abuse (if, for example, unexpected rib fractures are discovered), which would trigger mandatory reporting. Rather, the issue is dealt with only when there is a suspicion of abuse and usually in consultation with relevant experts. This approach, which avoids unnecessary harm and protects children who are potential victims of abuse, should also be adopted in the context of genetic testing.