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.

Mosaic trisomy 16, a rare chromosomal disorder, is compatible with life, therefore a baby can be born alive. This happens when only some of the cells in the body contain the extra copy of chromosome 16. Some of the consequences include slow growth before birth.

Human trisomies compatible with live birth, other than Down syndrome (trisomy 21), are Edwards syndrome (trisomy 18) and Patau syndrome (trisomy 13). Complete trisomies of other chromosomes are usually not viable and represent a relatively frequent cause of miscarriage. Only in rare cases of a mosaicism, the presence of a normal cell line, in addition to the trisomic cell line, may support the development of a viable trisomy of the other chromosomes.

During prenatal diagnosis the levels of trisomy in fetal-placental tissues can be analyzed. These levels can be predictors of outcomes in mosaic trisomy 16 pregnancies. In a study of prenatal diagnosis cases, there were 66% live births with an average 35.7 weeks gestational age. About 45% of them had malformations. The most common malformations were CSD, ASD, and hypospadias. However, trisomy 16 does not always result in anatomical abnormalities.

Assisted reproductive technology (ART) is a general term referring to methods used to achieve pregnancy by artificial or partially artificial means. According to the CDC, in general, ART procedures involve surgically removing eggs from a woman's ovaries, combining them with sperm in the laboratory, and returning them to the woman's body or donating them to another woman. ART has been associated with epigenetic syndromes, specifically BWS and Angelman syndrome. Three groups have shown an increased rate of ART conception in children with BWS. A retrospective case control study from Australia found a 1 in 4000 risk of BWS in their in-vitro population, several times higher than the general population. Another study found that children conceived by in vitro fertilisation (IVF) are three to four times more likely to develop the condition. No specific type of ART has been more closely associated with BWS. The mechanism by which ART produces this effect is still under investigation.

About half of all 'marker' chromosomes are idic(15) but idic(15) in itself is one of the rare chromosome abnormalities. Incidence at birth appears to be 1 in 30,000 with a sex ratio of almost 1:1; however, since dysmorphic features are absent or subtle and major malformations are rare, chromosome analysis may not be thought to be indicated, and some individuals, particularly in the older age groups, probably remain undiagnosed. There are organizations for families with idic(15) children that offer extensive information and support.

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.

Most pregnancies that are diagnosed with confined placental mosaicism continue to term with no complications and the children develop normally.

However, some pregnancies with CPM experience prenatal or perinatal complications. The pregnancy loss rate in pregnancies with confined placental mosaicism, diagnosed by chorionic villus sampling, is higher than among pregnancies without placental mosaicism. It may be that sometimes the presence of significant numbers of abnormal cells in the placenta interferes with proper placental function. An impaired placenta cannot support the pregnancy and this may lead to the loss of a chromosomally normal baby. On the other hand, an apparently normal diploid fetus may experience problems with growth or development due to the effects of uniparental disomy (UPD). Intrauterine growth restriction (IUGR) has been reported in a number of CPM cases. In follow-up studies adequate postnatal catch-up growth has been demonstrated, which may suggest a placental cause of the IUGR.

When predicting the likely effects (if any) of CPM detected in the first trimester, several potentially interactive factors may be playing a role, including:

- "Origin of error:" Somatic errors are associated with lower levels of trisomy in the placenta and are expected usually to involve only one cell line (i.e.: the trophoblast cells or the villus stroma cells). Somatic errors are thus less likely than meiotic errors to be associated with either ultrasound abnormalities, growth problems or detectable levels of trisomy in small samples of prenatal CVS. Currently, there is no evidence that somatic errors, which lead to confined placental trisomy, are of any clinical consequence. Errors of meiotic origin are correlated with higher levels of trisomy in placental tissues and may be associated with adverse pregnancy outcome. The cell type in which the abnormality is seen is also an important factor in determining the risk of fetal involvement. The villus stroma or mesenchymal core is more likely than the cytotrophoblast to be reflective of the fetal genotype.

- "Level of mosaicism:" There is a correlation between a high number of aneuploid cells detected at CVS with poor pregnancy progress. This includes an association between high levels of abnormal cells in placental tissue and concerns with the growth of the baby. However, it is not accurate to use these associations to try to predict pregnancy outcome based on the percent of trisomic cells in a first trimester CVS result.

- "Specific chromosomes:" The influence of CPM on fetal growth is chromosome specific. Certain chromosomes carry imprinted genes involved in growth or placental function, which may contribute to impaired pregnancy progress when CPM is detected. Different chromosomes are observed at different frequencies depending on the type of CPM observed. The pregnancy outcome is strongly chromosome specific. The most frequently seen trisomic cells in confined placental mosaicism involve chromosomes 2, 3, 7, 8 and 16. The next frequently involved are 9, 13, 15, 18, 20 and 22. It has been observed that CPM involving the sex chromosomes usually has no adverse effects on fetal development. The common autosomal trisomies (21, 18, 13) made up a smaller number of cases of mosaicism detected on CVS, but were more often confirmed in fetal tissue (19%). On the other hand, the uncommon autosomal trisomies accounted for a greater number of placental mosaicism cases, but were less often confirmed in fetal tissue (3.2%). When CPM is detected on CVS involving certain chromosomes which are known or suspected to carry imprinted genes, molecular investigations should be performed to exclude fetal UPD. We will explore chromosome specific cases in the chromosome specific section.

- "Type of chromosome abnormality:" The factor that had the highest predictive value as to whether the fetus was affected or not was the type of chromosome abnormality. Marker chromosomes were more often confirmed in the fetus than trisomies. For example, of 28 cases of mosaic polyploidy detected on CVS, fetal mosaicism was confirmed in only one case. This is compared to marker chromosomes detected on CVS, in which mosaicism was confirmed in 1/4 of the fetuses.

More than 80% of children with Patau syndrome die within the first year of life. Children with the mosaic variation are usually affected to a lesser extent. In a retrospective Canadian study of 174 children with trisomy 13, median survival time was 12.5 days. One and ten year survival was 19.8% and 12.9% respectively.

Research on the risk for developing schizophrenia in Ashkenazi Jews and other populations showed that 3q29 microdeletion syndrome leads to a significant higher rate of schizophrenia.

Craniofrontonasal dysplasia is a very rare genetic condition. As such there is little information and no consensus in the published literature regarding the epidemiological statistics.

The incidence values that were reported ranged from 1:100,000 to 1:120,000.

In general, the prognosis is very good. Children with BWS usually do very well and grow up to become the heights expected based on their parents' heights. While children with BWS are at increased risk of childhood cancer, most children with BWS do not develop cancer and the vast majority of children who do develop cancer can be treated successfully.

Children with BWS for the most part had no significant delays when compared to their siblings. However, some children with BWS do have speech problems that could be related to macroglossia or hearing loss.

Advances in treating neonatal complications and premature infants in the last twenty years have significantly improved the true infant mortality rate associated with BWS. In a review of pregnancies that resulted in 304 children with BWS, no neonatal deaths were reported. This is compared to a previously reported mortality rate of 20%. The data from the former study was derived from a BWS registry, a database that may be slightly biased towards involving living children; however, death was not an exclusion criterion to join the registry. This suggests that while infants with BWS are likely to have a higher than normal infant mortality risk, it may not be as high as 20%.

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%.

Chromosomal deletion syndromes result from deletion of parts of chromosomes. Depending on the location, size, and whom the deletion is inherited from, there are a few known different variations of chromosome deletions. Chromosomal deletion syndromes typically involve larger deletions that are visible using karyotyping techniques. Smaller deletions result in Microdeletion syndrome, which are detected using fluorescence in situ hybridization (FISH)

Examples of chromosomal deletion syndromes include 5p-Deletion (cri du chat syndrome), 4p-Deletion (Wolf-Hirschhorn syndrome), Prader–Willi syndrome, and Angelman syndrome.

Wolf–Hirschhorn syndrome (WHS), also known as chromosome deletion Dillan 4p syndrome, Pitt–Rogers–Danks syndrome (PRDS) or Pitt syndrome, was first described in 1961 by Americans Herbert L. Cooper and Kurt Hirschhorn and, thereafter, gained worldwide attention by publications by the German Ulrich Wolf, and Hirschhorn and their co-workers, specifically their articles in the German scientific magazine "Humangenetik". It is a characteristic phenotype resulting from a partial deletion of chromosomal material of the short arm of chromosome 4 (del(4p16.3)).

Wolf–Hirschhorn syndrome is a microdeletion syndrome caused by a deletion within HSA band 4p16.3 of the short arm of chromosome 4, particularly in the region of and . About 87% of cases represent a "de novo" deletion, while about 13% are inherited from a parent with a chromosome translocation. In the cases of familial translocation, there is a 2 to 1 excess of maternal transmission. Of the "de novo" cases, 80% are paternally derived. Severity of symptoms and expressed phenotype differ based on the amount of genetic material deleted. The critical region for determining the phenotype is at 4p16.3 and can often be detected through genetic testing and fluorescence in situ hybridization (FISH). Genetic testing and genetic counseling is offered to affected families.

At the present time, there is no specific treatment that can undo any chromosomal abnormality, nor the genetic pattern seen in people with idic(15). The extra chromosomal material in those affected was present at or shortly after conception, and its effects on brain development began taking place long before the child was born. Therapies are available to help address many of the symptoms associated with idic(15). Physical, occupational, and speech therapies along with special education techniques can stimulate children with idic(15) to develop to their full potential.

In terms of medical management of the symptoms associated with Chromosome 15q11.2-q13.1 Duplication Syndrome, families should be aware that individuals with chromosome 15 duplications may tolerate medications differently and may be more sensitive to side effects for some classes of medications, such as the serotonin reuptake inhibitor type medications (SSRI).

Thus, these should be used with caution and any new medication should be instituted in a controlled setting, with slow titration of levels and with a clear endpoint as to what the expected outcome for treatment is.

There is an increased risk of sudden, unexpected death among children and adults with this syndrome. The full cause is not yet understood but it is generally attributed to SUDEP (Sudden Unexplained Death in Epilepsy).

Confined placental mosaicism (CPM) represents a discrepancy between the chromosomal makeup of the cells in the placenta and the cells in the baby. CPM was first described by Kalousek and Dill in 1983. CPM is diagnosed when some trisomic cells are detected on chorionic villus sampling and only normal cells are found on a subsequent prenatal test, such as amniocentesis or fetal blood sampling. In theory, CPM is when the trisomic cells are found only in the placenta. CPM is detected in approximately 1-2% of ongoing pregnancies that are studied by chorionic villus sampling (CVS) at 10 to 12 weeks of pregnancy. Chorionic villus sampling is a prenatal procedure which involves a placental biopsy. Most commonly when CPM is found it represents a trisomic cell line in the placenta and a normal diploid chromosome complement in the baby. However, the fetus is involved in about 10% of cases.

Its exact cause is unknown, but present research points toward a genetic component, possibly following maternal genes.

It involves hypomethylation of "H19" and "IGF2". In 10% of the cases the syndrome is associated with maternal uniparental disomy (UPD) on chromosome 7. This is an imprinting error where the person receives two copies of chromosome 7 from the mother (maternally inherited) rather than one from each parent.

Like other imprinting disorders (e.g. Prader–Willi syndrome, Angelman syndrome, and Beckwith–Wiedemann syndrome), Silver–Russell syndrome may be associated with the use of assisted reproductive technologies such as in vitro fertilization.

Since the syndrome is caused by a genetic mutation in the individual's DNA, a cure is not available. Treatment of the symptoms and management of the syndrome, however, is possible.

Depending on the manifestation, surgery, increased intake of glucose, special education, occupational therapy, speech therapy, and physical therapy are some methods of managing the syndrome and associated symptoms.

3q29 microdeletion syndrome is a rare genetic disorder resulting from the deletion of a segment of chromosome 3. This syndrome was first described in 2005.

Isodisomy in a non-mendelian trait in humans caused by both copies of a chromosomal set being inherited from the biological mother or the father. It differs from uniparental disomy in that instead of receiving an identical set of chromosomes from one parent, the fertilized ovum contains a complete set of chromosomes from one parent resulting in a complete set of chromosomes from only one parent. This may result in the expression of recessive traits in the offspring. Some authors use the term uniparental disomy and isodisomy interchangeably.

This genetic abnormality can result in the birth of a normal child who has no obvious disability. It is associated with abnormalities in the growth of the offspring and in the placenta.

Raine syndrome (RNS), also called osteosclerotic bone dysplasia, is a rare autosomal recessive congenital disorder characterized by craniofacial anomalies including microcephaly, noticeably low set ears, osteosclerosis, a cleft palate, gum hyperplasia, a hypoplastic nose, and eye proptosis. It is considered to be a lethal disease, and usually leads to death within a few hours of birth. However, a recent report describes two studies in which children with Raine Syndrome have lived to 8 and 11 years old, so it is currently proposed that there is a milder expression that the phenotype can take (Simpson 2009).

It was first characterized in 1989 in a report that was published on an infant that had been born with an unknown syndrome, that later came to be called Raine Syndrome.

The current research describes Raine Syndrome as a neonatal osteosclerotic bone dysplasia, indicated by its osteosclerotic symptoms that are seen in those suffering from the disease. It has been found that a mutation in the gene FAM20C is the cause of the Raine Syndrome phenotype. This microdeletion mutation leads to an unusual chromosome 7 arrangement. The milder phenotypes of Raine Syndrome, such as those described in Simpson’s 2007 report, suggest that Raine Syndrome resulting from missense mutations may not be as lethal as the other described mutations (OMIM). This is supported by findings from Fradin et al. (2011), who reported on children with missense mutations to FAM20C and lived to ages 1 and 4 years, relatively much longer than the life spans of the previously reported children. Simpson et al.’s (2007) report states that to date, effected individuals have had chromosome 7 uniparental isodisomy and a 7p telomeric microdeletion. They had abnormal chromosome 7 arrangements, with microdeletions of their D7S2477 and D7S1484 markers (Simpson 2007).

Raine Syndrome appears to be an autosomal recessive disease. There are reports of recurrence in children born of the same parents, and an increased occurrence in children of closely related, genetically similar parents. Individuals with Raine Syndrome were either homozygous or compound heterozygous for the mutation of FAM20C. Also observed have been nonsynonomous mutation and splice-site changes (Simpson et al. 2007).

FAM20C, located on chromosome 7p22.3, is an important molecule in bone development. Studies in mice have demonstrated its importance in the mineralization of bones in teeth in early development (OMIM, Simpson et al. 2007, Wang et al. 2010). FAM20C stands for “family with sequence similarity 20, member C.” It is also commonly referred to as DMP-4. It is a Golgi-enriched fraction casein kinase and an extracellular serine/threonine protein kinase. It is 107,743 bases long, with 10 exons and 584 amino acids (Weizmann Institute of Science).

Patau syndrome is a syndrome caused by a chromosomal abnormality, in which some or all of the cells of the body contain extra genetic material from chromosome 13. The extra genetic material disrupts normal development, causing multiple and complex organ defects.

This can occur either because each cell contains a full extra copy of chromosome 13 (a disorder known as trisomy 13 or trisomy D), or because each cell contains an extra partial copy of the chromosome (i.e., Robertsonian translocation) or because of mosaic Patau syndrome. Full trisomy 13 is caused by nondisjunction of chromosomes during meiosis (the mosaic form is caused by nondisjunction during mitosis).

Like all nondisjunction conditions (such as Down syndrome and Edwards syndrome), the risk of this syndrome in the offspring increases with maternal age at pregnancy, with about 31 years being the average. Patau syndrome affects somewhere between 1 in 10,000 and 1 in 21,700 live births.

CFND is a very rare X-linked malformation syndrome caused by mutations in the ephrin-B1 gene (EFNB1). The EFNB1 gene codes for a membrane-anchored ligand which can bind to an ephrin tyrosine-kinase receptor. This ephrin receptor is, amongst other things, responsible for the regulation of embryonic tissue-border formation, and is important for skeletal and craniofacial development. As the ephrin receptor and its EFNB1 ligand are both bound to the (trans)membrane of the cell its cascade is activated through cell-cell interactions. These cell-cell interactions are disturbed due to the presence of cells with the mutant EFNB1 gene, as a result causing incomplete tissue-border formation.

Paradoxical to other X-linked conditions, with CFND the females are more severely affected than males. This is due to the process of X-inactivation in females, where at random either the maternal or paternal X-chromosome is inactivated in a cell. Due to this process the body’s tissues contain either cells with normal EFNB1 or the mutated EFNB1. This is called a mosaic pattern. This mosaic pattern of cells 'interferes' with the functionality of the cell-cell interactions, as a result causing the severe physical malformations in females.

As with all X-linked conditions CFND has a preset chance of being passed down from parents to their offspring. Females have two X-chromosomes and males have one X-chromosome. When a mother is a carrier of CFND, there is a 50% chance of her passing down the X-chromosome containing the mutated EFNB1 gene to her offspring, regardless if the child is a boy or girl. If the father is a carrier there is a 100% chance of him passing down his X-chromosome with the EFNB1 mutation to a daughter, and 0% chance of him passing it down to a son.