Locations can include:

- subcutaneous tissue/scalp

- pleura (pleural effusion)

- pericardium (pericardial effusion)

- abdomen (ascites)

The edema is usually seen in the fetal subcutaneous tissue, sometimes leading to spontaneous abortion. It is a prenatal form of heart failure, in which the heart is unable to satisfy its demand for a high amount of blood flow.

Hydrops fetalis is a condition in the fetus characterized by an accumulation of fluid, or edema, in at least two fetal compartments. By comparison, hydrops allantois or hydrops amnion is an accumulation of excessive fluid in the allantoic or amniotic space, respectively.

Twin-to-twin transfusion syndrome (TTTS), also known as feto-fetal transfusion syndrome (FFTS) and twin oligohydramnios-polyhydramnios sequence (TOPS) is a complication of disproportionate blood supply, resulting in high morbidity and mortality. It can affect monochorionic multiples, that is, multiple pregnancies where two or more fetuses share a chorion and hence a single placenta. Severe TTTS has a 60–100% mortality rate.

A staging system proposed by fetal surgeon Dr. Ruben Quintero is commonly used to classify the severity of TTTS.

Stage I: A small amount of amniotic fluid (oligohydramnios) is found around the donor twin and a large amount of amniotic fluid (polyhydramnios) is found around the recipient twin.

Stage II: In addition to the description above, the ultrasound is not able to identify the bladder in the donor twin.

Stage III: In addition to the characteristics of Stages I and II, there is abnormal blood flow in the umbilical cords of the twins.

Stage IV: In addition to all of the above findings, the recipient twin has swelling under the skin and appears to be experiencing heart failure (fetal hydrops).

Stage V: In addition to all of the above findings, one of the twins has died. This can happen to either twin. The risk to either the donor or the recipient is roughly equal & is quite high in Stage II or higher TTTS.

The Quintero staging does not provide information about prognosis, and other staging systems have been proposed.

Fetal disease refers to disorders originating in utero.

Examples include hydrops fetalis and chorioamnionitis

Mirror syndrome or triple oedema or Ballantyne syndrome is a rare disorder affecting pregnant women. It describes the unusual association of fetal

and placental hydrops with maternal preeclampsia.

The name "mirror syndrome" refers to the similarity between maternal oedema and fetal hydrops. It was first described in 1892 by John William Ballantyne.

Ballantyne syndrome has several characteristics:

- edema, always a key feature

- albuminuria of the mother, usually mild

- preeclampsia, unusual

The fetal symptoms are related to fluid retention, including ascites and polyhydramnios.

Fetal hydrops suggests the presence of an important and probably fatal fetal pathology.

It can be associated with twin-to-twin transfusion syndrome.

Types of breech depend on how the baby’s legs are lying.

- A frank breech (otherwise known as an extended breech) is where the baby’s legs are up next to its abdomen, with its knees straight and its feet next to its ears. This is the most common type of breech.

- A complete breech (flexed) breech is when the baby appears as though it is sitting crossed-legged with its legs bent at the hips and knees.

- A footling breech is when one or both of the baby’s feet are born first instead of the pelvis. This is more common in babies born prematurely or before their due date.

In addition to the above, breech births in which the sacrum is the fetal denominator can be classified by the position of a fetus. Thus sacro-anterior, sacro-transverse and sacro-posterior positions all exist, but left sacro-anterior is the most common presentation. Sacro-anterior indicates an easier delivery compared to other forms.

A breech birth occurs when a baby is born bottom first instead of head first. Around 3-5% of pregnant women at term (37–40 weeks pregnant) will have a breech baby.

Most babies in the breech position are born by a caesarean section because it is seen as safer than being born vaginally.

As most breech babies are delivered by caesarean section in developed countries, doctors and midwives may lose the skills required to safely assist women giving birth to a breech baby vaginally. Delivering all breech babies by caesarean section in developing countries may be very difficult to implement or even impossible as there are not always resources available to provide this service.

Neonatal hypoglycemia is a transient or temporary condition of decreased blood sugar or hypoglycemia in a neonate.

Temporary hypoglycemia in the first three hours after birth is a normal finding. Most of the time it resolves without medical intervention. The lowest blood sugars occur one to two hours after birth. After this time, lactose begins to be available through the breast milk. In addition, gluconeogenesis occurs when the kidneys and liver convert fats into glucose..

Pulmonary hypoplasia is incomplete development of the lungs, resulting in an abnormally low number or size of bronchopulmonary segments or alveoli. A congenital malformation, it most often occurs secondary to other fetal abnormalities that interfere with normal development of the lungs. Primary (idiopathic) pulmonary hypoplasia is rare and usually not associated with other maternal or fetal abnormalities.

Incidence of pulmonary hypoplasia ranges from 9–11 per 10,000 live births and 14 per 10,000 births. Pulmonary hypoplasia is a relatively common cause of neonatal death. It also is a common finding in stillbirths, although not regarded as a cause of these.

Rh disease (also known as rhesus isoimmunisation, Rh (D) disease, rhesus incompatibility, rhesus disease, RhD hemolytic disease of the newborn, rhesus D hemolytic disease of the newborn or RhD HDN) is a type of hemolytic disease of the newborn (HDN). The disease ranges from mild to severe, and typically occurs only in some second or subsequent pregnancies of Rh negative women where the fetus's father is Rh positive, leading to a Rh+ pregnancy. During birth, the mother may be exposed to the infant's blood, and this causes the development of antibodies, which may affect the health of subsequent Rh+ pregnancies. In mild cases, the fetus may have mild anaemia with reticulocytosis. In moderate or severe cases the fetus may have a more marked anaemia and erythroblastosis fetalis (hemolytic disease of the newborn). When the disease is very severe it may cause hydrops fetalis or stillbirth.

Rh disease is generally preventable by treating the mother during pregnancy or soon after delivery with an intramuscular injection of anti-RhD immunoglobulin (Rho(D) immune globulin). The RhD protein is coded by the RHD gene.

Frequently, the thrombocytopenia is mild and the affected neonates remain largely asymptomatic. In these cases, therapeutic interventions are not indicated. In case of severe thrombocytopenia, the neonates may exhibit hemorrhagic complication at or a few hours after delivery. The most serious complication is intracranial hemorrhage, leading to death in approximately 10% or neurologic sequelae in 20% of cases.

Hemolytic disease of the newborn (anti-Rhc) can range from a mild to a severe disease. It is the third most common cause of severe HDN. Rh disease is the most common and hemolytic disease of the newborn (anti-Kell) is the second most common cause of severe HDN.

It occurs more commonly in women who are Rh D negative.

Cystic hygromas are increasingly diagnosed by prenatal ultrasonography. A common symptom is a neck growth. It may be found at birth, or discovered later in an infant after an upper respiratory tract infection. Cystic hygromas can grow very large and may affect breathing and swallowing. Some symptoms may include a mass or lump in the mouth, neck, cheek, or tongue. It feels like a large fluid-filled sac. In addition, cystic hygromas can be found in other body parts such as the arm, chest, legs, groin, and buttocks. Cystic hygromas are also often seen in Turner's syndrome, although a patient who does not have Turner's syndrome can present with this condition.

Neonatal alloimmune thrombocytopenia (NAITP, NAIT, NATP or NAT) is a disease that affects babies in which the platelet count is decreased. Platelet antigens are inherited from both mother and father. is caused by antibodies specific for platelet antigens inherited from the father but which are absent in the mother. Fetomaternal transfusions (or fetomaternal hemorrhage) results in the recognition of these antigens by the mother's immune system as non-self, with the subsequent generation of allo-reactive antibodies which cross the placenta. , hence, is caused by transplacental passage of maternal platelet-specific alloantibody and rarely human leukocyte antigen () allo-antibodies (which are expressed by platelets) to fetuses whose platelets express the corresponding antigens. occurs in somewhere between 1/800 and 1/5000 live births. More recent studies of seem to indicate that it occurs in around 1/600 live births in the Caucasian population.

Hemolytic disease of the newborn, also known as hemolytic disease of the fetus and newborn, HDN, HDFN, or erythroblastosis fetalis, is an alloimmune condition that develops in a fetus, when the IgG molecules (one of the five main types of antibodies) produced by the mother pass through the placenta. Among these antibodies are some which attack antigens on the red blood cells in the fetal circulation, breaking down and destroying the cells (hemolysis). The fetus can develop reticulocytosis and anemia. This fetal disease ranges from mild to very severe, and fetal death from heart failure (hydrops fetalis) can occur. When the disease is moderate or severe, many erythroblasts (immature red blood cells) are present in the fetal blood, and so these forms of the disease can be called "erythroblastosis fetalis" (or "erythroblastosis foetalis").

HDFN represents a breach of immune privilege for the fetus or some other form of impairment of the immune tolerance of pregnancy. Various types of HDFN are classified by which alloantigen provokes the response. In order of incidence, the types include ABO, anti-RhD, anti-RhE, anti-Rhc, anti-Rhe, anti-RhC, multiantigen combinations, and anti-Kell.

Causes of pulmonary hypoplasia include a wide variety of congenital malformations and other conditions in which pulmonary hypoplasia is a complication. These include congenital diaphragmatic hernia, congenital cystic adenomatoid malformation, fetal hydronephrosis, caudal regression syndrome, mediastinal tumor, and sacrococcygeal teratoma with a large component inside the fetus. Large masses of the neck (such as cervical teratoma) also can cause pulmonary hypoplasia, presumably by interfering with the fetus's ability to fill its lungs. In the presence of pulmonary hypoplasia, the EXIT procedure to rescue a baby with a neck mass is not likely to succeed.

Fetal hydrops can be a cause, or conversely a complication.

Pulmonary hypoplasia is associated with oligohydramnios through multiple mechanisms. Both conditions can result from blockage of the urinary bladder. Blockage prevents the bladder from emptying, and the bladder becomes very large and full. The large volume of the full bladder interferes with normal development of other organs, including the lungs. Pressure within the bladder becomes abnormally high, causing abnormal function in the kidneys hence abnormally high pressure in the vascular system entering the kidneys. This high pressure also interferes with normal development of other organs. An experiment in rabbits showed that PH also can be caused directly by oligohydramnios.

Pulmonary hypoplasia is associated with dextrocardia of embryonic arrest in that both conditions can result from early errors of development, resulting in Congenital cardiac disorders.

PH is a common direct cause of neonatal death resulting from pregnancy induced hypertension.

Three quarters of affected patients are asymptomatic. However, 25% develop cyanosis, pneumothorax, and show signs of increased breathing difficulty ( tachypnoea and intercostal retractions).

At examination, they may show hyper-resonance at percussion, diminished vesicular murmur and an asymmetrical thorax.

Signs of hemolytic disease of the newborn include a positive direct Coombs test (also called direct agglutination test), elevated cord bilirubin, and hemolytic anemia. It is possible for a newborn with this disease to have neutropenia and neonatal alloimmune thrombocytopenia as well.Hemolysis leads to elevated bilirubin levels. After delivery bilirubin is no longer cleared (via the placenta) from the neonate's blood and the symptoms of jaundice (yellowish skin and yellow discoloration of the whites of the eyes) increase within 24 hours after birth. Like other severe neonatal jaundice, there is the possibility of acute or chronic kernicterus, however the risk of kernicterus is higher because of the rapid destruction of blood cells. It is important to note that isoimmunization is a risk factor for neurotoxicity and lowers the level at which kernicterus can occur. Untreated profound anemia can cause high-output heart failure, with pallor, enlarged liver and/or spleen, generalized swelling, and respiratory distress.

HDN can be the cause of hydrops fetalis, an often-severe form of prenatal heart failure that causes fetal edema.

Congenital pulmonary airway malformation (CPAM), formerly known as congenital cystic adenomatoid malformation (CCAM), is a congenital disorder of the lung similar to bronchopulmonary sequestration. In CPAM, usually an entire lobe of lung is replaced by a non-working cystic piece of abnormal lung tissue. This abnormal tissue will never function as normal lung tissue. The underlying cause for CPAM is unknown. It occurs in approximately 1 in every 30,000 pregnancies.

In most cases the outcome of a fetus with CPAM is very good. In rare cases, the cystic mass grows so large as to limit the growth of the surrounding lung and cause pressure against the heart. In these situations, the CPAM can be life-threatening for the fetus. CPAM can be separated into five types, based on clinical and pathologic features. CPAM type 1 is the most common, with large cysts and a good prognosis. CPAM type 2 (with medium-sized cysts) often has a poor prognosis, owing to its frequent association with other significant anomalies. Other types are rare.

A cystic hygroma, also known as cystic lymphangioma and macrocystic lymphatic malformation, is an often congenital multiloculated lymphatic lesion that can arise anywhere, but is classically found in the left posterior triangle of the neck and armpits. This is the most common form of lymphangioma. It contains large cyst-like cavities containing lymph, a watery fluid that circulates throughout the lymphatic system. Microscopically, cystic hygroma consists of multiple locules filled with lymph. In the depth, the locules are quite big but they decrease in size towards the surface.

Cystic hygromas are benign, but can be disfiguring. It is a condition which usually affects children; very rarely it can present in adulthood.

Cystic hygroma is also known as lymphatic malformation. Currently, the medical field prefers to use the term lymphatic malformation because the term cystic hygroma means water tumor. Lymphatic malformation is more commonly used now because it is a sponge-like collection of abnormal growth that contains clear lymphatic fluid. The fluid collects within the cysts or channels, usually in the soft tissue. Cystic hygromas occur when the lymphatic vessels that make up the lymphatic system are not formed properly. There are two types of lymphatic malformations. They are macrocystic lymphatic malformations, large cysts, and microcystic, small cysts. A person may have only one kind of the malformation or can have a mixture of both macro and micro cysts.

Cystic hygroma can be associated with a nuchal lymphangioma or a fetal hydrops. Additionally, it can be associated with Turner syndrome or with Noonan syndrome.

A lethal version of this condition is known as Cowchock Wapner Kurtz syndrome that, in addition to cystic hygroma, includes cleft palate and lymphedema, a condition of localized edema and tissue swelling caused by a compromised lymphatic system.

Usually associated with diaphragmatic hernia,

pulmonary hypoplasia,

imperforate anus,

micropenis,

bilateral cryptorchidism,

cerebral ventricular dilation,

camptodactyly,

agenesis of sacrum,

low-set ear.

- Fryns et al. (1979) reported 2 stillborn sisters with a multiple congenital anomaly syndrome characterized by coarse facies with cloudy corneae, diaphragmatic defects, absence of lung lobulation, and distal limb deformities. A sporadic case was reported by Goddeeris et al. (1980). Fitch (1988) claimed that she and her colleagues were the first to describe this disorder. In 1978 they reported a single infant, born of second-cousin parents, who had absent left hemidiaphragm, hydrocephalus, arhinencephaly, and cardiovascular anomalies.

- Lubinsky et al. (1983) reported a brother and sister with Fryns syndrome who both died in the neonatal period. Facial anomalies included broad nasal bridge, microretrognathia, abnormal helices, and cleft palate. Other features included distal digital hypoplasia, lung hypoplasia, and urogenital abnormalities, including shawl scrotum, uterus bicornis, and renal cysts. They were discordant for diaphragmatic hernia, cleft lip, and Dandy–Walker anomaly.

- Meinecke and Fryns (1985) reported an affected child; consanguinity of the parents supported recessive inheritance. They noted that a diaphragmatic defect had been described in 4 of the 5 reported cases and lung hypoplasia in all. Young et al. (1986) reported a sixth case. The male infant survived for 12 days. These authors listed corneal clouding, camptodactyly with hypoplastic nails, and abnormalities of the diaphragm as cardinal features.

- Samueloff et al. (1987) described a family in which all 4 children had Fryns syndrome and neonatal mortality. Features included hypoplastic lungs, cleft palate, retrognathia, micrognathism, small thorax, diaphragmatic hernia, distal limb hypoplasia, and early onset of polyhydramnios with premature delivery. Schwyzer et al. (1987) described an affected infant whose parents were second cousins.

- Moerman et al. (1988) described infant brother and sister with the syndrome of diaphragmatic hernia, abnormal face, and distal limb anomalies. Both died shortly after birth with severe respiratory distress. Ultrasonography demonstrated fetal hydrops, diaphragmatic hernia, and striking dilatation of the cerebral ventricles in both infants. Post-mortem examination showed Dandy–Walker malformation, ventricular septal defect, and renal cystic dysplasia.

- Cunniff et al. (1990) described affected brothers and 3 other cases, bringing the total reported cases of Fryns syndrome to 25. One of the affected brothers was still alive at the age of 24 months. Bilateral diaphragmatic hernias had been repaired on the first day of life. He required extracorporeal membrane oxygenation therapy for 5 days and oscillatory therapy for 3 months. Ventriculoperitoneal shunt was required because of slowly progressive hydrocephalus. Scoliosis was associated with extranumerary vertebral bodies and 13 ribs. Because of delayed gastric emptying, a gastrostomy tube was inserted. In addition, because of persistent chylothorax, he underwent decortication of the right lung and oversewing of the thoracic duct.

- Kershisnik et al. (1991) suggested that osteochondrodysplasia is a feature of Fryns syndrome.

- Willems et al. (1991) suggested that a diaphragmatic hernia is not a necessary feature of Fryns syndrome. They described a child with all the usual features except for diaphragmatic hernia; the diaphragm was reduced to a fibrous web with little muscular component. Bartsch et al. (1995) presented 2 unrelated cases with a typical picture of Fryns syndrome but without diaphragmatic hernia. One of these patients was alive at the age of 14 months, but was severely retarded. Bamforth et al. (1987) and Hanssen et al. (1992) also described patients with this syndrome who survived the neonatal period. In the report of Hanssen et al. (1992), 2 older sibs had died in utero. The reports suggested that survival beyond the neonatal period is possible when the diaphragmatic defect and lung hypoplasia are not present. However, mental retardation has been present in all surviving patients.

- Vargas et al. (2000) reported a pair of monozygotic twins with Fryns syndrome discordant for severity of diaphragmatic defect. Both twins had macrocephaly, coarse facial appearance, hypoplasia of distal phalanges, and an extra pair of ribs. Twin A lacked an apparent diaphragmatic defect, and at 1 year of age had mild developmental delay. Twin B had a left congenital diaphragmatic hernia and died neonatally. The authors suggested that absence of diaphragmatic defect in Fryns syndrome may represent a subpopulation of more mildly affected patients.

- Aymé, "et al." (1989) described 8 cases of Fryns syndrome in France. The most frequent anomalies were diaphragmatic defects, lung hypoplasia, cleft lip and palate, cardiac defects, including septal defects and aortic arch anomalies, renal cysts, urinary tract malformations, and distal limb hypoplasia. Most patients also had hypoplastic external genitalia and anomalies of internal genitalia, including bifid or hypoplastic uterus or immature testes. The digestive tract was also often abnormal; duodenal atresia, pyloric hyperplasia, malrotation and common mesentery were present in about half of the patients. When the brain was examined, more than half were found to have Dandy–Walker anomaly and/or agenesis of the corpus callosum. A few patients demonstrated cloudy cornea. Histologically, 2 of 3 patients showed retinal dysplasia with rosettes and gliosis of the retina, thickness of the posterior capsule of the lens, and irregularities of Bowman membrane.

- Alessandri et al. (2005) reported a newborn from the Comores Islands with clinical features of Fryns syndrome without diaphragmatic hernia. They noted that diaphragmatic hernia is found in more than 80% of cases and that at least 13 other cases had been reported with an intact diaphragm.

- In a postneonatal survivor of Fryns syndrome, Riela et al. (1995) described myoclonus appearing shortly after birth, which was well controlled on valproate. Progressive cerebral and brainstem atrophy was noted on serial MRIs made at 3 months and after 6 months of age.

- Van Hove et al. (1995) described a boy with Fryns syndrome who survived to age 3 years and reviewed the outcome of other reported survivors (approximately 14% of reported cases). Survivors tended to have less frequent diaphragmatic hernia, milder lung hypoplasia, absence of complex cardiac malformation, and severe neurologic impairment. Their patient had malformations of gyration and sulcation, particularly around the central sulcus, and hypoplastic optic tracts beyond the optic chiasm associated with profound mental retardation.

- Fryns and Moerman (1998) reported a second-trimester male fetus with Fryns syndrome and midline scalp defects. The authors stated that the finding of a scalp defect in Fryns syndrome confirms that it is a true malformation syndrome with major involvement of the midline structures.

- Ramsing et al. (2000) described 2 sibships with 4 fetuses and 1 preterm baby of 31 weeks' gestation affected by a multiple congenital disorder suggestive of Fryns syndrome. In addition to the diaphragmatic defects and distal limb anomalies, they presented with fetal hydrops, cystic hygroma, and multiple pterygias. Two affected fetuses in 1 family showed severe craniofacial abnormalities with bilateral cleft lip and palate and cardiovascular malformation.

- Arnold et al. (2003) reported a male fetus with Fryns syndrome and additional abnormalities, in particular, multiple midline developmental defects including gastroschisis, central nervous system defects with left arrhinencephaly and cerebellar hypoplasia, midline cleft of the upper lip, alveolar ridge, and maxillary bone, and cleft nose with bilateral choanal atresia.

- Pierson et al. (2004) reviewed 77 reported patients with Fryns syndrome and summarized the abnormal eye findings identified in 12 of them. They also described 3 new patients with Fryns syndrome, 1 of whom demonstrated unilateral microphthalmia and cloudy cornea.

- Slavotinek et al. (2005) noted that Fryns syndrome may be the most common autosomal recessive syndrome in which congenital diaphragmatic hernia (see DIH2, 222400) is a cardinal feature. The autosomal recessive inheritance in Fryns syndrome contrasts with the sporadic inheritance for most patients with DIH.

Hemolytic disease of the newborn (anti-Kell) is the second most common cause of severe hemolytic disease of the newborn (HDN) after Rh disease. Anti-Kell is becoming relatively more important as prevention of Rh disease is also becoming more effective.

Hemolytic disease of the newborn (anti-Kell) is caused by a mismatch between the Kell antigens of the mother and fetus. About 91% of the population are Kell negative and about 9% are Kell positive. A fraction of a percentage are homozygous for Kell. Therefore, about 4.5% of babies born to a Kell negative mother are Kell positive.

The disease results when maternal antibodies to Kell are transferred to the fetus across the placental barrier, breaching immune privilege. These antibodies can cause severe anemia by interfering with the early proliferation of red blood cells as well as causing alloimmune hemolysis. Very severe disease can occur as early as 20 weeks gestation. Hydrops fetalis can also occur early. The finding of anti-Kell antibodies in an antenatal screening blood test (indirect Coombs test) is an indication for early referral to a specialist service for assessment, management and treatment.