Glossary of Terms

airway obstruction

In some fetuses, a tumor or other anomaly of the neck may cause pressure on the trachea (wind pipe), making it difficult for the baby to breathe at birth. (During pregnancy, the fetus does not "breathe" with his lungs, but receives oxygen through the placenta.) If it is anticipated that the baby will not be able to breathe at birth because of this neck lesion, an EXIT procedure may be necessary.


The sampling of amniotic fluid by aspiration through a fine needle, which is inserted through the mother’s abdominal wall (under local anesthesia) into the uterus (amniotic cavity). This is usually done under ultrasound guidance.


A technique (not very often used today) to look directly at the embryo or fetus. A fine telescope is inserted into the uterus, either through the abdominal wall or through the vagina. The embryo can be observed inside his amniotic (fluid) sac. The amniotic cavity itself is not entered with this procedure. This technique can only be performed in the first 3 months of pregnancy. After that, the amniotic membrane is fused with the wall of the uterus, and the technique of inserting a telescope inside the womb (and inside the amniotic cavity) is called fetoscopy.


An irregular or abnormal heart beat. These include abnormally high heart rates such as atrial flutter.

atrial flutter

A type of fetal arrhythmia that can sometimes be treated by giving medicine to the mother (which will pass through the placenta and affect the fetus).


A doctor who treats conditions of the heart.


A technique or machine to study the heart rate of the fetus.

chorionic villus sampling

The sampling of cells from the fetal portion of the placenta, to study the chromosomes of the fetus. This technique is usually done between 10 and 12 weeks of gestation.

cord blood A blood sample from the fetus (to study chromosomes, for example) can be obtained by inserting a fine needle into the umbilical cord, under ultrasound guidance.
Congenital diaphragmatic hernia

Some fetuses have an incompletely formed diaphragm (the thin layer of muscle separating the chest cavity from the abdomen. As a result, intestines (and sometimes a portion of the liver) move into the chest through the hole in the diaphragm, and compress the lungs. In many cases, this pressure is so severe that the lungs cannot develop properly, and the newborn may have serious respiratory problems. Most often, treatment for this condition occurs at birth, but several centers worldwide are exploring the possibility to treat the condition before birth.

Doppler ultrasound

The Doppler effect is the pitch difference of a sound traveling toward, or away from the observer (think of the siren’s pitch dropping as an ambulance drives by). In ultrasound used to look specifically at the anatomy and function of the heart.


A specialized form of ultrasound (that includes Doppler ultrasound) to specifically analyze the anatomy and function of the fetal heart.


Ex-Utero-Intrapartum procedure (EXIT) is a very specialized form of Cesarean section used when severe airway obstruction is expected at birth. The uterus is carefully opened to allow only the upper body of the fetus to be exposed. The fetus remains attached to umbilical cord and receives oxygen through the placenta, until the airway is secured. Only then is the umbilical cord clamped and is the baby fully delivered.

fetal cells in maternal blood

Normally, the blood circulation of the fetus is completely separate from the mother’s. In some conditions, however, cells from the fetus cross the placental barrier and can be found in the maternal blood circulation. Analysis of these cells can sometimes help reach a diagnosis of certain fetal conditions.

fetal development

How the embryo and fetus develop into a newborn baby is still not fully understood. As imaging techniques are becoming more sophisticated, our understanding of normal fetal development is improving. Still, it is sometimes difficult to differentiate normal development or normal variants from actual anomalies when interpreting prenatal images (ultrasound or MRI)


The technique of looking into the womb through a narrow telescope, usually inserted through the mother’s abdominal wall. This is done under local or general anesthesia. It allows direct observation of the fetus and the placenta, and can be used to perform surgical interventions as well. The most commonly performed fetoscopic operation is laser ablation of placental vessels in twin-to-twin transfusion syndrome.


A doctor who specializes in genetic disorders.


Heart failure of the fetus. It often shows as an abnormal accumulation of fluid around the heart or the lungs, in the abdomen (ascites) and under the skin (edema, or swelling).

magnetic resonance imaging

MRI is a form of medical imaging that utilizes the specific properties of molecules to create images of internal organs. Unlike XRays or CT scan, it does not generate radiation.

maternal-fetal medicine

Also called perinatology; a specialized branch of obstetrics that deals with high-risk pregnancies and fetal disorders.

MOMS trial

A prospective study sponsored by the National Institutes of Health to examine the benefits, if any, of fetal surgery for spina bifida.


Maternal Serum Alpha-Fetoprotein (AFP): AFP is a protein that is abundantly present in the fetus. In certain fetal conditions, such as spina bifida and gastroschisis (a defect of the abdominal wall of the fetus), it leaks out into the amniotic fluid and can be detected in the blood of the mother. Elevated MSAFP can be an indication of any of these conditions. Conversely, a low MSAFP may suggest that the fetus has Down syndrome.


A treatment or medical management that utilizes a team of physicians and other health care providers from many different specialties.

myelomeningocele Also called spina bifida or Open Neural Tube defect: a condition whereby the spinal cord, which should be protected by the spine and covered by skin, is partially exposed through a hole in the back. Children affected by spina bifida may have a number of anomalies that include weakness or paralysis of the legs.

A doctor who specializes in the care of premature infants.

nuchal translucency

A finding on fetal ultrasound that may indicate the presence of Down syndrome, as well as other fetal conditions. It refers to the transparency and thickness of the skin of the back of the neck.

open neural tube defect

See myelomeningocele.


See Maternal-Fetal Medicine.


The prediction of a disease’s outcome.

quadruple test

A screening test for Down syndrome that uses a combination of MSAFP and three other markers: Estriol, hCG and inhibin.

screening test

A relatively simple and inexpensive test that can be administered rapidly to a large number of “at risk” individuals. The focus of a screening test is to catch all patients affected by a certain disease (high sensitivity), even if it falsely identifies individuals who are not affected (specificity). Once someone is screened positive, a (more complex and/or expensive, but also more specific) test must be administered to confirm the disease.

spina bifida

See myelomeningocele.

surgical specialist

Surgeons usually specialize in a particular age group (pediatric surgeons operate on infants and children) or in a specific organ or organ system (neurosurgeons operate on the brain and the spinal cord, urologists operate the kidneys and urinary tract, for example).

three-dimensional ultrasound

A specialized form of ultrasound that gives a 3-D image, rather than the usual two-dimensional picture.

triple test

Similar to the “quadruple test” for Down syndrome, but without inhibin.

twin-to-twin transfusion syndrome

A condition seen in 15% of identical twins, whereby one fetus (the donor) continuously ‘gives’ blood to the other twin (the recipient), through connecting blood vessels on the placenta.

ultrasound A medical imaging test that measures how different tissues and organs absorb and/or reflect sound waves. A computer analyzes the strength of these signals to create a two-dimensional image of the internal organs. This is the most commonly used form of fetal diagnosis.