The vast majority of triple X women are never diagnosed, unless they undergo tests for other medical reasons later in life. Triple X can be diagnosed by a blood test which is able to look at a person’s chromosomes (karyotype). Abnormalities on the electroencephalography may be present.

Triple X syndrome can be diagnosed prenatally through amniocentesis or chorionic villus sampling. In Denmark, between 1970 and 1984, 76% of the prenatally diagnosed fetuses with triple-X were aborted. Between 1985-1987, this figure dropped to 56%. With improved information, the number of abortions diminished. In the Netherlands, between 1991 and 2000, 33% (18/54) of the couples that were confronted with a prenatal diagnosis of 47, XXX elected to abort. If balanced information is provided to prospective parents, prenatally, the incidence of voluntary termination (abortion) is reduced.

About 92% of pregnancies in Europe with a diagnosis of Down syndrome are terminated. In the United States, termination rates are around 67%, but this rate varied from 61% to 93% among different populations evaluated. When nonpregnant people are asked if they would have a termination if their fetus tested positive, 23–33% said yes, when high-risk pregnant women were asked, 46–86% said yes, and when women who screened positive are asked, 89–97% say yes.

When screening tests predict a high risk of Down syndrome, a more invasive diagnostic test (amniocentesis or chorionic villus sampling) is needed to confirm the diagnosis. If Down syndrome occurs in one in 500 pregnancies and the test used has a 5% false-positive rate, this means, of 26 women who test positive on screening, only one will have Down syndrome confirmed. If the screening test has a 2% false-positive rate, this means one of eleven who test positive on screening have a fetus with DS. Amniocentesis and chorionic villus sampling are more reliable tests, but they increase the risk of miscarriage between 0.5 and 1%. The risk of limb problems is increased in the offspring due to the procedure. The risk from the procedure is greater the earlier it is performed, thus amniocentesis is not recommended before 15 weeks gestational age and chorionic villus sampling before 10 weeks gestational age.

Diagnosis of 48, XXXY is usually done by a standard karyotype. A karyotype is a chromosomal analysis in which a full set of chromosomes can be seen for an individual. The presence of the additional 2 X chromosomes on the karyotype are indicative of XXXY syndrome.

Another way to diagnosis 48, XXXY is by chromosomal microarray showing the presence of extra X chromosomes. Chromosomal microarray (CMA) is used to detect extra or missing chromosomal segments or whole chromosomes. CMA uses microchip-based testing to analyze many pieces of DNA. Males with 48, XXXY are diagnosed anywhere from before birth to adulthood as a result of the range in the severity of symptoms. The age range at diagnosis is likely due to the fact that XXXY is a rare syndrome, and does not cause as extreme phenotypes as other variants of Klinefelter syndrome (such as XXXXY).

Diagnostic testing could also be done via blood samples. Elevated levels of follicle stimulating hormone, luteinizing hormone, and low levels of testosterone can be indicative of this syndrome.

About 10% of Klinefelter cases are found by prenatal diagnosis. The first clinical features may appear in early childhood or, more frequently, during puberty, such as lack of secondary sexual characteristics and aspermatogenesis. Despite the presence of small testes, only a quarter of the affected males are recognized as having Klinefelter syndrome at puberty. Another quarter receive their diagnosis in late adulthood. About 64% of affected individuals are never recognized. Often the diagnosis is made incidentally as a result of examinations and medical visits for reasons not linked to the condition.

The standard diagnostic method is the analysis of the chromosomes' karyotype on lymphocytes. In the past, the observation of the Barr body was common practice as well. To confirm mosaicism, it is also possible to analyze the karyotype using dermal fibroblasts or testicular tissue.

Other methods may be: research of high serum levels of gonadotropins (follicle-stimulating hormone and luteinizing hormone), presence of azoospermia, determination of the sex chromatin, and prenatally via chorionic villus sampling or amniocentesis. A 2002 literature review of elective abortion rates found that approximately 58% of pregnancies in the United States with a diagnosis of Klinefelter syndrome were terminated.

The symptoms of Klinefelter syndrome are often variable; therefore, a karyotype analysis should be ordered when small testes, infertility, gynecomastia, long legs/arms, developmental delay, speech/language deficits, learning disabilities/academic issues and/or behavioral issues are present in an individual. The differential diagnosis for the Klinefelter syndrome can include the following conditions: fragile X syndrome, Kallmann syndrome and Marfan syndrome. The cause of hypogonadism can be attributed to many other different medical conditions.

There have been some reports of individuals with Klinefelter syndrome who also have other chromosome abnormalities, such as Down syndrome.

47,XYY syndrome is not usually diagnosed until learning issues are present. The syndrome is diagnosed in an increasing number of children prenatally by amniocentesis and chorionic villus sampling in order to obtain a chromosome karyotype, where the abnormality can be observed.

It is estimated that only 15–20% of children with 47,XYY syndrome are diagnosed within their lifetime. Of these, approximately 30% are diagnosed prenatally. For the rest of those diagnosed after childbirth, around half are diagnosed during childhood or adolescence due to developmental delays or learning difficulties. The rest are diagnosed for a variety of reasons including a small percentage due to fertility problems (5%).

Patients have an essentially normal life expectancy but require regular medical follow-up.

Pre-implantation genetic diagnosis (PGD or PIGD) is a technique used to identify genetically normal embryos and is useful for couples who have a family history of genetic disorders. This is an option for people choosing to procreate through IVF. PGD is considered difficult due to it being both time consuming and having success rates only comparable to routine IVF.

Exposure of spermatozoa to lifestyle, environmental and/or occupational hazards may increase the risk of aneuploidy. Cigarette smoke is a known aneugen (aneuploidy inducing agent). It is associated with increases in aneuploidy ranging from 1.5 to 3.0-fold. Other studies indicate factors such as alcohol consumption, occupational exposure to benzene, and exposure to the insecticides fenvalerate and carbaryl also increase aneuploidy.

A karyotype is done to diagnose XXYY syndrome. Treatment consists of medications, behavioral therapies and intensive community support.

Around 1 in 1,000 boys are born with a 47,XYY karyotype. The incidence of 47,XYY is not known to be affected by the parents' ages.

In general, idic(15) occurs de novo but the parents must be karyotyped to make sure it is not inherited, mostly because this will affect the course of genetic counseling given to the family. If the abnormality is found prenatally and one of the parents harbour the marker, the child has a chance of not carrying the mutation. Further tests should however be done to prove the marker has not been rearranged while being inherited. This information is also necessary for counseling of future pregnancies. Each family is unique and should therefore be handled individually.

As the syndrome is due to a chromosomal non-disjunction event, the recurrence risk is not high compared to the general population. There has been no evidence found that indicates non-disjunction occurs more often in a particular family.

Triple X syndrome occurs in around 1 in 1,000 girls. On average, five to ten girls with triple X syndrome are born in the United States each day.

The extra chromosome in people with idic(15) can be easily detected through chromosome analysis (karyotyping). Additional tests are usually required. FISH (Fluorescent in situ hybridization) is used to confirm the diagnosis by distinguishing idic(15) from other supernumerary marker chromosomes. Array CGH can be used to determine the gene content and magnitude of copy number variation so that the clinical picture can be foreseen.

Interstitial duplications of chromosome 15 can be more difficult to detect on a routine chromosome analysis but are clearly identifiable using a 15q FISH study. Families should always discuss the results of chromosome and FISH studies with a genetic counselor or other genetics professionals to ensure accurate interpretation.

Edwards syndrome occurs in about one in 5,000 live births, but more conceptions are affected by the syndrome because the majority of those diagnosed with the condition prenatally will not survive to birth. Although women in their 20s and early 30s may conceive babies with Edwards syndrome, the risk of conceiving a child with it increases with a woman's age. The average maternal age for conceiving a child with this disorder is 32½.

In 2008/2009, 495 diagnoses of Edwards syndrome (trisomy 18) were made in England and Wales, 92% of which were made prenatally, resulting in 339 abortions, 49 stillbirths/miscarriages/fetal deaths, 72 unknown outcomes, and 35 live births. Because about 3% of cases with unknown outcomes are likely to result in a live birth, the total number of live births is estimated to be 37 (2008/09 data are provisional). Major causes of death include apnea and heart abnormalities. It is impossible to predict an exact prognosis during pregnancy or the neonatal period. Half of the infants with this condition do not survive beyond the first week of life. The median lifespan is five to 15 days. About 8-12% of infants survive longer than 1 year. One percent of children live to age 10, though a retrospective Canadian study of 254 children with trisomy 18 demonstrated ten year survival of 9.8%.

Treatment of Aicardi syndrome primarily involves management of seizures and early/continuing intervention programs for developmental delays.

Additional comorbidities and complications sometimes seen with Aicardi syndrome include porencephalic cysts and hydrocephalus, and gastro-intestinal problems. Treatment for porencephalic cysts and/or hydrocephalus is often via a shunt or endoscopic of the cysts, though some require no treatment. Placement of a feeding tube, fundoplication, and surgeries to correct hernias or other gastrointestinal structural problems are sometimes used to treat gastro-intestinal issues.

Aicardi syndrome is typically characterized by the following triad of features - however, one of the "classic" features being missing does not preclude a diagnosis of Aicardi Syndrome, if other supporting features are present.

1. Partial or complete absence of the corpus callosum in the brain (agenesis of the corpus callosum);

2. Eye abnormalities known as "lacunae" of the retina that are quite specific to this disorder; [optic nerve coloboma]]; and

3. The development in infancy of seizures that are called infantile spasms.

Other types of defects of the brain such as microcephaly, polymicrogyria, porencephalic cysts and enlarged cerebral ventricles due to hydrocephalus are also common in Aicardi syndrome.

As its name indicates, a person with the syndrome has one Y chromosome and four X chromosomes on the 23rd pair, thus having 49 chromosomes rather than the normal 46. As with most categories of aneuploidy disorders, 49,XXXXY syndrome is often accompanied by intellectual disability. It can be considered a form of 47, XXY Klinefelter syndrome, or a variant of it.

It is genetic but not hereditary. This means that while the genes of the parents cause the syndrome, there is a small chance of more than one child having the syndrome. The probability of inheriting the disease is about 1%.

The individuals with this syndrome are males, but 49, XXXXX also exists with similar characteristics.

XLI can be suspected based on clinical findings, although symptoms can take varying amounts of time to become evident, from a few hours after birth, up to a year in milder cases. The diagnosis is usually made by a dermatologist, who also typically formulates the treatment plan (see below). STS enzyme deficiency is confirmed using a clinically available biochemical assay. Carrier detection can be performed in mothers of affected sons using this test (see Genetics, below). Molecular testing for DNA deletions or mutations is also offered, and can be particularly useful in the evaluation of individuals with associated medical conditions (see below). Prenatal diagnosis is possible using either biochemical or molecular tests. However, the use of prenatal diagnosis for genetic conditions that are considered to be generally benign raises serious ethical considerations and requires detailed genetic counseling.

49,XXXXY syndrome is an extremely rare aneuploidic sex chromosomal abnormality. It occurs in approximately 1 out of 85,000 to 100,000 males.

Due to the wide range of genetic disorders that are presently known, diagnosis of a genetic disorder is widely varied and dependent of the disorder. Most genetic disorders are diagnosed at birth or during early childhood, however some, such as Huntington's disease, can escape detection until the patient is well into adulthood.

The basic aspects of a genetic disorder rests on the inheritance of genetic material. With an in depth family history, it is possible to anticipate possible disorders in children which direct medical professionals to specific tests depending on the disorder and allow parents the chance to prepare for potential lifestyle changes, anticipate the possibility of stillbirth, or contemplate termination. Prenatal diagnosis can detect the presence of characteristic abnormalities in fetal development through ultrasound, or detect the presence of characteristic substances via invasive procedures which involve inserting probes or needles into the uterus such as in amniocentesis.

Not all genetic disorders directly result in death, however there are no known cures for genetic disorders. Many genetic disorders affect stages of development such as Down syndrome. While others result in purely physical symptoms such as muscular dystrophy. Other disorders, such as Huntington's disease show no signs until adulthood. During the active time of a genetic disorder, patients mostly rely on maintaining or slowing the degradation of quality of life and maintain patient autonomy. This includes physical therapy, pain management, and may include a selection of alternative medicine programs.