About one third of children whose mothers are taking this drug during pregnancy typically have intrauterine growth restriction with a small head and develop minor dysmorphic craniofacial features and limb defects including hypoplastic nails and distal phalanges (birth defects). A smaller population will have growth problems and developmental delay, or intellectual disability. Methemoglobinemia is a rarely seen side effect.

Heart defects and cleft lip may also be featured.

Fetal trimethadione syndrome is characterized by the following major symptoms as a result of the teratogenic characteristics of trimethadione.

- Cranial and facial abnormalities which include; microcephaly, midfacial flattening, V-shaped eyebrows and a short nose

- Cardiovascular abnormalities

- Absent kidney and ureter

- Meningocele, a birth defect of the spine

- Omphalocele, a birth defect where portions of the abdominal contents project into the umbilical cord

- A in mental and physical development

Fetal hydantoin syndrome, also called fetal dilantin syndrome is a group of defects caused to the developing fetus by exposure to teratogenic effects of phenytoin or carbamazepine. Dilantin is the brand name of the drug phenytoin sodium in the United States, commonly used in the treatment of epilepsy.

It may also be called congenital hydantoin syndrome, Fetal Hydantoin Syndrome, Dilantin Embryopathy, or Phenytoin Embryopathy.

Association with EPHX1 has been suggested.

Fetal trimethadione syndrome (also known as paramethadione syndrome, German syndrome, tridione syndrome, among others) is a set of birth defects caused by the administration of the anticonvulsants trimethadione (also known as Tridione) or paramethadione to epileptic mothers during pregnancy.

Fetal trimethadione syndrome is classified as a rare disease by the National Institute of Health's Office of Rare Diseases, meaning it affects less than 200,000 individuals in the United States.

The fetal loss rate while using trimethadione has been reported to be as high as 87%.

Infants with Catel–Manzke syndrome have an extra (supernumerary), irregularly shaped bone known as a Hyperphalangy located between the first bone of the index finger (proximal phalanx) and the corresponding bone within the body of the hand (second metacarpal). As a result, the index fingers may be fixed in an abnormally bent position (clinodactyly). In some rare cases, additional abnormalities of the hands may also be present. Due to the presence of micrognathia, glossoptosis, and cleft palate, affected infants may have feeding and breathing difficulties; growth deficiency; consistent middle ear infections (otitis media); and other complications.

In addition, some infants with the syndrome may have structural abnormalities of the heart that are present at birth (congenital heart defects). The range and severity of symptoms and findings may vary from case to case. Catel–Manzke syndrome usually appears to occur randomly, for unknown sporadic reasons.

Catel–Manzke syndrome is a rare genetic disorder characterized by distinctive abnormalities of the index fingers; the classic features of Pierre Robin syndrome; occasionally with additional physical findings. "Pierre Robin syndrome" refers to a sequence of abnormalities that may occur as a distinct syndrome or as part of another underlying disorder. Pierre Robin syndrome is characterized by an unusually small jaw (micrognathia), downward displacement or retraction of the tongue (glossoptosis), and incomplete closure of the roof of the mouth (cleft palate). It is also linked to hyper mobility syndrome.

Craniofacial and other features of LFS include: maxillary hypoplasia (underdevelopment of the upper jaw bone), a small mandible (lower jaw bone) and receding chin, a high-arched palate (the roof of the mouth), with crowding and misalignment of the upper teeth; macrocephaly (enlarged skull) with a prominent forehead, hypernasal speech (voice), a long nose with a high, narrow nasal bridge; a deep, short philtrum (the indentation in the upper lip, beneath the nose), low-set ears with some apparent retroversion, hypotonia (decreased muscle tone), pectus excavatum (a malformity of the chest), slightly enlarged to normal testicular size in males, and seizures.

Hypernasal speech, or "hypernasality", is primarily the result of velopharyngeal insufficiency, a sometimes congenital aberration in which the velopharyngeal sphincter allows too much air into the nasal cavity during speech. In LFS, hypernasality may also be caused by failure of the soft palate and uvula to reach the back wall of the pharynx (the interior cavity of the throat where swallowing generally occurs) during speech, a condition that can be associated with a submucosal cleft palate.

It can be detected by the naked eye as well as dental or skull X-Ray testing.

LFS is clinically distinguished from other X-linked forms of intellectual disability by the accompanying presence of marfanoid habitus. Marfanoid habitus describes a group of physical features common to Marfan syndrome. Including Marfan syndrome and LFS, marfanoid features of this type have also been observed with several other disorders, one of which is multiple endocrine neoplasia type 2.

In LFS, specific features identified as marfanoid include: a long, narrow face; tall, thin stature; long, slender limbs, fingers and toes (not unlike arachnodactyly) with joint hyperextensibility, shortened halluces (the big toes) and long second toes.

The diagnosis of marfanoid habitus in LFS is often delayed because many of the physical features and characteristics associated with it are usually not evident until adolescence.

The most common facial features of SLOS include microcephaly, bitemporal narrowing (reduced distance between temples), ptosis, a short and upturned nose, micrognathia, epicanthal folds, and capillary hemangioma of the nose. Other physical characteristics include:

- low-set and posteriorly rotated ears

- high-arched, narrow, hard palate

- cleft lip/palate

- agenesis or hypoplasia of the corpus callosum

- cerebellar hypoplasia

- increased ventricular size

- decreased frontal lobe size

- polydactyly of hands or feet

- short, proximally placed thumb

- other finger malformations

- syndactyly of second and third toes

- ambiguous or female-like male genitalia

- congenital heart defects

- renal, pulmonary, liver and eye abnormalities

Nager acrofacial dysostosis is a genetic congenital anomaly syndrome. Nager syndrome displays several or all of the following characteristics: underdevelopment of the cheek and jaw area, down-sloping of the opening of the eyes, lack or absence of the lower eyelashes, kidney or stomach reflux, hammer toes, shortened soft palate, lack of development of the internal and external ear, possible cleft palate, underdevelopment or absence of the thumb, hearing loss (see hearing loss with craniofacial syndromes) and shortened forearms, as well as poor movement in the elbow, and may be characterized by accessory tragi. Occasionally, affected individuals develop vertebral anomalies such as scoliosis. The inheritance pattern is said to be autosomal but there are arguments as to whether it is autosomal dominant or autosomal recessive. Most cases tend to be sporadic. Nager syndrome is also linked to five other similar syndromes: Miller syndrome, Treacher Collins, Pierre Robin, Genee-Wiedemann, and Franceschetti-Zwahlen-Klein.

It causes facial abnormalities, skeletal malformation and occasionally neural tube defects; the skeletal disfigurements resolve to a degree in the course of development.

Mutations in different parts of the gene may lead to deafness or Stickler syndrome type III (eye problems: myopia, retinal detachment and skeletal abnormalities).

Infants and children: Infants that are born with Weissenbacher-Zweymüller syndrome usually have short bones in their arms and legs. The thigh and upper arm bones are wider than usual resulting in a dumbbell-shape while the bones of the vertebrae may be abnormal. Typical abnormal facial features can be wide-set protruding eyes (hypertelorism), a small and upturned nose with a flat bridge, small jaw (micrognathia) and a cleft palate. Some infants have high-frequency hearing loss. Infants may also exhibit a psychomotor delay. After the period of growth deficiency the individual makes improvements in bone growth leading to a normal physical development around age 5 or 6.

Adults: Many with Weissenbacher-Zweymüller syndrome have a catch-up growth phase causing the adults to not be unusually short. Many adults still will have hearing loss and typical abnormal facial features of Weissenbacher-Zweymüller syndrome.

Facial femoral syndrome is a rare congenital disorder. It is also known as femoral dysgenesis, bilateral femoral dysgenesis, bilateral-Robin anomaly and femoral hypoplasia-unusual facies syndrome. The main features of this disorder are underdeveloped thigh bones (femurs) and unusual facial features.

For individuals with MORM syndrome, symptoms do not appear until about one year into the child’s life span. From conception to birth, individuals with MORM syndrome appear asymptotic with no abnormal characteristics. Vision is negatively affected within the first year of life, particularly night vision. Individuals with MORM syndrome experience decreased visual acuity meaning their ability to see distinct sharp lines decreases. Vision quality continues to deteriorate until age three. Any further reduction in vision acuity is not observed until the individual is between the ages thirty to forty. Delayed sentence processing and intellectual disability is associated with individuals with MORM syndrome, primarily observed at age four. Individuals continue to develop and grow until they are five to twelve years old. During this age bracket, truncal obesity can develop. Truncal obesity is a term used to describe the build up of fat around ones trunk or torso as opposed to the persons extremities. Males enter puberty at around age twelve and develop normally except for their sex organ. The males penis will remain at the prepubescent size resulting in a micropenis. The life span of individuals with MORM syndrome is unclear as well as the fertility of these individuals.

Nager syndrome is thought to be caused by haploinsufficiency of the spliceosomal factor SF3B4.

Aphalangy, hemivertebrae and urogenital-intestinal dysgenesis is an extremely rare syndrome, described only in three siblings. It associates hypoplasia or aplasia of phalanges of hands and feet, hemivertebrae and various urogenital and/or intestinal abnormalities. Intrafamilial variability is important as one sister had lethal abnormalities (Potter sequence and pulmonary hypoplasia), while her affected brother was in good health with normal psychomotor development at 6 months of age. Prognosis seems to depend mainly on the severity of visceral malformations. Etiology and inheritance remain unknown.

While not always pathological, it can present as a birth defect in multiple syndromes including:

- Catel–Manzke syndrome

- Bloom syndrome

- Coffin–Lowry syndrome

- congenital rubella

- Cri du chat syndrome

- DiGeorge's syndrome

- Ehlers-Danlos syndrome

- fetal alcohol syndrome

- Hallermann-Streiff syndrome

- Hemifacial microsomia (as part of Goldenhar syndrome)

- Juvenile idiopathic arthritis

- Marfan syndrome

- Noonan syndrome

- Pierre Robin syndrome

- Prader–Willi syndrome

- Progeria

- Russell-Silver syndrome

- Seckel syndrome

- Smith-Lemli-Opitz syndrome

- Treacher Collins syndrome

- Trisomy 13 (Patau syndrome)

- Trisomy 18 (Edwards syndrome)

- Wolf–Hirschhorn syndrome

- X0 syndrome (Turner syndrome)

Pierre Robin syndrome (abbreviated to PRS, and also known as Pierre Robin sequence, Pierre Robin malformation, Pierre Robin anomaly or Pierre Robin anomalad) is a congenital condition of facial abnormalities in humans. PRS is a sequence, i.e. a chain of certain developmental malformations, one entailing the next. The three main features are cleft palate, retrognathia (abnormal positioning of the jaw or mandible) and glossoptosis (airway obstruction caused by backwards displacement of the tongue base). A genetic cause to PRS was recently identified. Pierre Robin sequence may be caused by genetic anomalies at chromosomes 2, 11, or 17.

The hearing loss associated with Stickler syndrome can be progressive and usually involves the high frequencies. Sensorineural hearing loss has been reported in as many as 100% and as low as 20% of affected individuals. A conductive loss due to otitis can magnify an existing sensorineural loss and is a frequent problem for children with Stickler or Marshall Syndrome.

The most severe problem associated with Stickler syndrome is Pierre Robin syndrome. This refers to a cleft palate resulting from a very small lower jaw. During early fetal life, the roof of the mouth is normally open and the sides of the palate have to come together to close. If the jaw is too small, there is not enough room for the tongue which is then pushed up and gets in the way of the closing palate. Sometimes the chin is so small the baby has problems with eating and breathing if the tongue blocks the back of the throat. Cleft palate is found less frequently in Marshall Syndrome than in Stickler syndrome but still more frequently than in the general population.

The facial features of Marshall Syndrome include a flat midface, the appearance of large eyes, short upturned nose, and a round face. The facial features of Stickler syndrome are less prominent but include a rather long flat face, and depressed nasal bridge.

PRS is characterized by an unusually small mandible (micrognathia), posterior displacement or retraction of the tongue (glossoptosis), and upper airway obstruction. Incomplete closure of the roof of the mouth (cleft palate) is present in the majority of patients, and is commonly U-shaped.

SLOS can present itself differently in different cases, depending on the severity of the mutation and other factors. Originally, SLOS patients were classified into two categories (classic and severe) based on external behaviours, physical characteristics, and other clinical features. Since the discovery of the specific biochemical defect responsible for SLOS, patients are given a severity score based on their levels of cerebral, ocular, oral, and genital defects. It is then used to classify patients as having mild, classical, or severe SLOS.

The cause of this condition is not known. A genetic basis is suspected. More than one case have been reported in three families.

First arch syndromes are congenital defects caused by a failure of neural crest cells to migrate into the first pharyngeal arch. They can produce facial anomalies. Examples of first arch syndromes include Treacher Collins syndrome and Pierre Robin syndrome.

The failure of the metanephros to develop in cases of BRA and some cases involving unilateral renal agenesis (URA) is due primarily to the failure of the mesonephric duct to produce a ureteric bud capable of inducing the metanephric mesenchyme. The failed induction will thereby cause the subsequent degeneration of the metanephros by apoptosis and other mechanisms. The mesonephric duct(s) of the agenic kidney(s) will also degenerate and fail to connect with the bladder. Therefore, the means by which the fetus produces urine and transports it to the bladder for excretion into the amniotic sac has been severely compromised (in the cases of URA), or completely eliminated (in the cases of BRA). The decreased volume of amniotic fluid causes the growing fetus to become compressed by the mother's uterus. This compression can cause many physical deformities of the fetus, most common of which is Potter facies. Lower extremity anomalies are frequent in these cases, which often presents with clubbed feet and/or bowing of the legs. Sirenomelia, or "Mermaid syndrome" (which occurs approximately in 1:45,000 births) can also present. In fact, nearly all reported cases of sirenomelia also be present with BRA.

Other anomalies of the classic Potter sequence infant include a parrot beak nose, redundant skin, and the most common characteristic of infants with BRA which is a skin fold of tissue extending from the medial canthus across the cheek. The ears are slightly low and pressed against the head making them appear large. The adrenal glands often appear as small oval discs pressed against the posterior abdomen due to the absence of upward renal pressure. The bladder is often small, nondistensible and may be filled with a minute amount of fluid. In males the vas deferens and seminal vesicles may be absent, while in females the uterus and upper vagina may be absent. Other abnormalities include anal atresia, absence of the rectum and sigmoid colon, esophageal and duodenal atresia, and a single umbilical artery. Presence of a diaphragmatic hernia is also common in these fetuses/infants. Additionally, the alveolar sacs of the lungs fail to properly develop as a result of the reduced volume of amniotic fluid. Labor is often induced between 22 and 36 weeks of gestation (however, some of these pregnancies may go to term) and unaborted infants typically survive for only a few minutes to a few hours. These infants will eventually die as either a result of pulmonary hypoplasia or renal failure.