Pregnancy Terms Glossary
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Aarskog syndrome ; Aarskog-Scott syndrome (AAS); faciogenital dysplasia.

A condition characterized by slight to moderate short stature, hypertelorism, small nose with anteverted nares, broad philtrum, orthodontic problems, brachydactyly, prominent umbilicus,  and shawl scrotum. A spectrum of behavioral disorders may be part of the AAS phenotype. May be at increased risk for mental deficiency.  The condition is transmitted by mutations in a gene called FGDY1 in band p11.21 on the X chromosome and follows an X-linked recessive inheritance (sex-linked) pattern.

See Also: Online Mendelian Inheritance in Man®



Abdomen (The Belly)

The body cavity below the chest that contains the stomach, liver, intestines and other organs.


Abdominal circumference (AC)

The distance around fetal abdomen.

The abdominal circumference is measured by sonogram from outer skin surface to outer skin surface

The appropriate transverse plane for measurement of the fetal abdominal circumference (AC) should include the umbilical vein at the level where the umbilical vein enters the liver. The ossification centers of the spine should be aligned.

 

    UV =Umbilical vein           S= Spine


Abortion

 

Abruptio placenta (Placental abruption)

Partial or complete separation of the placenta from the uterus before delivery. It happens  in  0.8-1.0% of all pregnancies and has a high recurrence rate. Contractions are usually present. Bleeding is also present in approximately 80% of patients. Factors that have been associated with abruption include maternal hypertension, intrauterine growth restriction (IUGR), non-vertex presentation, polyhydramnios, advanced maternal age, maternal smoking, cocaine use, chorioamnionitis, premature rupture of membranes, and blunt external maternal trauma


āc

 Before meals


Acceleration

An acceleration is an abrupt increase in the fetal heart rate above baseline with onset to peak of the acceleration less than 30 seconds and less than 2 minutes in duration.

Adequate accelerations are defined as:

  •  In a fetus less than 32 weeks' gestation an increase in heart rate greater than or equal to 10 beats per minute above baseline for greater than or equal to 10 seconds.
  •  In a fetus greater than 32 weeks' gestation an increase in heart rate greater than or equal to 15 beats per minute above baseline for greater than or equal to 15 seconds.

Acromelia

Shortening of the hands or feet


Active Labor

The active phase (active labor) of labor begins when the cervix is opened (dilated) to 6 cm in the presence of uterine contractions. During the active phase uterine contractions become more frequent, the cervix dilates more quickly, and the baby descends into the pelvis.


Agenesis of the corpus callosum (ACC)

A birth defect in which there is partial or complete absence of the corpus callosum (the bundle of nerve fibers that connects the two hemispheres of the brain). 

ACC may occur as an isolated defect, but it is frequently associated with other malformations, chromosomal abnormalities (trisomy 18 an trisomy 8), and genetic syndromes. The outcome of the abnormality depends on the underlying cause and the presence of other structural defects. Isolated ACC (in particular partial ACC) is associated with no or mild neurologic impairment in a large proportion of cases. ACC occurring as part of a syndrome may be associated with severe mental retardation and seizures. ACC does not cause death in the majority of children.

Ultrasound findings include absence of the corpus callosum and cavum septum pellucidum, 'teardrop' configuration of the lateral ventricles, dilatation and upward  displacement of the third ventricle (interhemispheric "cyst") , and abnormal branching of the anterior cerebral artery. Magnetic resonance imaging is sometimes useful in confirming the diagnosis. 

Additional abnormalities commonly found in association with ACC include include Chiari malformations, schizencephaly, encephaloceles, Dandy-Walker malformations, holoprosencephaly, heart defects, and GI or genitourinary malformations.

The risk of recurrence is ~ 1% for sporadic cases, 25% if ACC is associated with an  autosomal recessive cause, and 50% of males will be affected if inherited as an  X-linked recessive disorder.


Akinesia

Absence or lack of movement


Alloimmunization (Isoimmunization)

Production of an antibody against antigens produced by members of the same species.
 

Alpha-fetoprotein (AFP)

A protein produced by the fetal liver and yolk sac that can be detected in the mother's blood. Alpha-fetoprotein levels rise gradually throughout most of pregnancy and level off near term. High levels of alpha-fetoprotein are associated with a more advanced pregnancy than expected, multiple pregnancy, fetal death (including a vanished twin), an opening in the spine (spina bifida), an opening in the head (anencephaly), or an opening in the abdominal wall (gastroschisis).  Low levels may be associated with Down syndrome, trisomy 18, and some cases of Turner syndrome.


Amniocentesis

A procedure in which a needle is inserted into the uterus and a sample of the fluid surrounding the fetus is drawn out. The procedure may be done to evaluate the fetal chromosomes, to determine fetal lung maturity, or to obtain fluid to culture for possible infections. The procedure may also be performed to remove an excessive amount of amniotic fluid.


Amniotic fluid

The liquid that surrounds the fetus. Amniotic fluid is nearly all fetal urine with a small amount of fluid contributed by the lungs.


Amniotic Fluid Index (AFI)

An ultrasound procedure used to asses the amount of amniotic fluid. The amniotic fluid index is measured by dividing the uterus into four imaginary quadrants. The deepest, unobstructed, vertical pocket of fluid is measured in each quadrant. The four pocket measurements are then added to calculate the AFI. A normal AFI is between 5 and 25 cm.


Amniotic sac

The membrane (amnion) that surrounds the fetus and the amniotic fluid.


Anemia

Decreased amount of normal hemoglobin in blood. Hemoglobin is the substance in red blood cells that carries oxygen.


Anencephaly

A birth defect resulting in the absence of a major portion of the skull and brain. Anencephaly results when the upper portion of the neural tube fails to close. The condition is not compatible with life, and infants usually die within a few days after delivery. See picture


Angelman syndrome ("Happy Puppet Syndrome")

A disorder characterized by a large jaw and open-mouthed expression revealing the tongue, severe speech impairment, motor and intellectual retardation, ataxia, poor muscle tone, seizures, frequent laughing, smiling, and excitability. The disorder is usually caused by abnormalities of chromosome 15. 

A deletion of chromosome in the 15q11-q13 region accounts for up to 75% of cases and has a less than 1% recurrence risk. Mutations in the UBE3A gene on chromosome 15 accounts for 6 to 20% of cases and has a recurrence risk of less than 1% unless the patient's mother carries the UBE3A mutation on her own paternally inherited chromosome 15. In the latter case there is a 50% recurrence risk. Angelman syndrome is less commonly caused by inheritance of two copies of chromosome 15 from the father and no maternal copy of chromosome 15 (uniparental disomy) , or mutations in the imprinting center of the UBE3A gene.


Aniridia

Absent or partially absent iris accompanied by macular and optic nerve hypoplasia. Symptoms include poor vision  sensitivity to light (photophobia), and nystagmus. Frequently associated  abnormalities  include glaucoma and cataracts.  Mutation of the PAX 6 gene or deletion of a regulatory region controlling its expression, appears to be responsible for aniridia occurring  as an isolated ocular defect . The condition is autosomal dominant.

Aniridia may also occur as part of the Wilms tumor-aniridia-genital anomalies-retardation (WAGR) syndrome, with a deletion of 11p13 involving the PAX6 (aniridia) locus and the adjacent WT1 (Wilms tumor) locus.


Antenatal

Before birth.


Antenatal steroids

Steroids (either betamethasone or dexamethasone) given to help the fetal lungs and other organs mature more rapidly. Antenatal steroids are given when preterm delivery is anticipated between 24 and 34 weeks' gestation with intact membranes, and at 24 to 32 weeks' with ruptured membranes.


Antepartum

Before delivery or birth.


Antibody (Immunoglobulin)

Molecules produced by white blood cells (lymphocytes) that attach to foreign molecules. Antibodies (immunoglobulins) are grouped into five classes or isotypes: IgG, IgA, IgM, IgD, and IgE.

A molecules that stimulates antibody production is called an antigen (antibody generator). 


Anticardiolipin antibody

An antibody that attaches to cardiolipin
 


Anti-c antibody (little c antibody)

A protein made by the immune system that binds to a molecule called the c antigen found on the surface of red blood cells. The c antigen is part of the Rhesus blood group system which consists of several antigens (D , E , e , c, C, ). The antibody hastens removal of the c antigen (and the foreign blood cells) from the body.

Anti-c antibody is capable of crossing the placenta and causing anemia in the fetus and hemolytic disease of the newborn. Pregnancies complicated by anti-c antibody are managed as for Rh-D sensitization .


Anti-D antibody (Rh sensitization, Rh disease)

A protein made by the immune system that binds to a molecule called the D antigen found on the surface of red blood cells. The D antigen is part of the Rhesus blood group system which consists of several antigens (D , E , e , c, C, ). The antibody hastens removal of the D antigen (and the foreign blood cells) from the body.

Anti-D antibody is capable of crossing the placenta and causing SEVERE anemia in the fetus and hemolytic disease of the newborn.


Anti-Duffy antibody (anti-Fya antibody)

A protein made by the immune system that binds to a molecule called the Fya antigen found on the surface of red blood cells. The Fya antigen is part of the Duffy blood group system which consists of the antigens Fya and Fyb . The antibody hastens removal of the and Fya antigen (and the foreign blood cells) from the body.

Anti-Fya antibody is capable of crossing the placenta and causing SEVERE anemia in the fetus and hemolytic disease of the newborn. Anti-Fyb has not been reported to cause significant hemolytic disease of the newborn.


Anti-Kell antibody

A protein made by the immune system that binds to a molecule called the Kell antigen found on red blood cells. The Kell antigen is part of the Kell blood group system which consists of several antigens ( Kell or K1 , Kpa, k  , Jsa  ,Jsb ). The antibody hastens removal of the Kell antigen (and the foreign blood cells) from the body.

Anti-Kell antibody is capable of crossing the placenta and causing SEVERE anemia in the fetus and hemolytic disease of the newborn.
SEE ALSO: Q & A ..a pregnant patient with anti-Kell antibodies...


Anti-Kidd antibody (anti-Jka  or anti-Jkb)

A protein made by the immune system that binds to a molecule called Kidd antigen found on the surface of red blood cells. The Kidd antigens Jk and Jkb are part of the Kidd blood group system.

Anti-Kidd antibody is capable of crossing the placenta and causing anemia in the fetus and hemolytic disease of the newborn.


Anti-Lewis antibody

A protein made by the immune system that binds to molecules called the Lewis antigens,  Le a and Le b. Lewis antigens are not made by the red blood cell, but are antigens present in body fluids and secretions that have been adsorbed onto the surface of the red blood cell. Lewis antigens are found in very low levels on the fetal red cells.

Most Lewis antibodies are of the IgM type and do not cross the placenta. Lewis blood group antibodies are not known to cause hemolytic disease of the newborn.


Anti-S antibody

A protein made by the immune system that bind to a molecule called the S antigen found on the surface of red blood cells. The S antigen is part of the MNS blood group system which consists of several antigens ( M, S,s, N)

Anti-S antibody is capable of crossing the placenta and causing anemia in the fetus and hemolytic disease of the newborn.


Apgar Score


Arcuate uterus

Midline thickening of the wall of the uterus at the uterine fundus (top of the uterus). The thickened area results from failure to completely dissolve the uterine septum during development. The arcuate uterus is considered to be a mild form of bicornuate uterus. An arcuate uterus does not appear to have an unfavorable effect on pregnancy.
 



Arthrogryposis

A group of disorders characterized by immobility of the joints present at birth. The condition may be caused by underlying abnormalities of the nervous system, muscles, or connective tissues, or limitations to movement while in the uterus. Arthrogryposis has been described as a feature of numerous syndromes including congenital myasthenia gravis,  perinatal lethal Gaucher disease, and Freeman-Shelton syndrome to name just a few. Some forms affect nearly all of the major joints. Other forms of arthrogryposis may involve primarily the hands and feet (distal arthrogryposis). The course and outcome of the disorder will depend on the underlying cause of the arthrogryposis and normal development of the lungs.

Amyoplasia (Arthrogryposis Multiplex Congenita) accounts for more than 40% of children with arthrogryposis.  Although these infants will require orthopedic and rehabilitative interventions during their childhood, their functional outcome in both physical and educational areas is excellent. The condition is sporadic.

About one-third of children born with arthrogryposis have a severe or lethal form of Pena-Shokeir phenotype or lethal multiple pterygium syndrome. These infants usually do not survive past the neonatal period. Pena-Shokeir and lethal multiple pterygium are often inherited as autosomal recessive traits.

Ultrasound findings may include increased amniotic fluid level, decreased movement, knocked knees, clubfeet, and clubbed hands.

The risk of recurrence is ~ 1% for sporadic cases, 25% if arthrogryposis is associated with an  autosomal recessive cause, 50% if inherited as an autosomal dominant trait, and 50% of males will be affected if inherited as an  X-linked recessive disorder. When the specific diagnosis is unknown, there is a 5 percent chance that another child will be born with the same condition or that an affected adult will have an affected child.


Arnold-Chiari Malformation

A group of birth defects of the cerebellum (the part of the brain that controls balance) and base of the skull characterized by downward displacement of the cerebellum and related structures below the level of the foramen magnum (the large hole at the base of the skull).

The three types of Arnold-Chiari malformation are:

  • Type I: The fourth ventricle (the fluid filled cavity between the cerebellum and pons of the brainstem) remains in its normal position. The lower most structures of the cerebellum (the cerebellar tonsils) are displaced through the foramen magnum.

    Many persons with a Type I malformation have no symptoms. However, some persons may experience headache that is aggravated by coughing and straining, weakness or loss of sensation of the upper arms and hands, slurred speech, trouble swallowing, dizziness, or trouble balancing.

  • Type II: The fourth ventricle is at the level of the foramen magnum. The cerebellar tonsils, parts of the cerebellum,  pons, and medulla oblongata are displaced through the foramen magnum. Typically accompanied by hydrocephalus and myelomeningocele (open spina bifida).

  • Type III: Displacement of the fourth ventricle in addition to the the cerebellum,  pons, and medulla oblongata through the foramen magnum. Usually ccompanied by encephalocele or myelomeningocele .

Ascites

 


Augmentation of  labor

Stimulation the uterus to increase the frequency, duration , or strength of contractions when spontaneous contractions have failed to cause dilation or thinning (effacement) of the cervix leading to the delivery of the infant.

1. World Health Organization. Managing Complications in Pregnancy and Childbirth .A guide for midwives and doctors. 2003. http://who.int/reproductive-health/impac/Procedures/Induction_P17_P25.html ACOG Practice Bulletin No. 49.
2. American College of Obstetricians and Gynecologists. Dystocia and augmentation of labor.Obstet Gynecol 2003;102:1445–54.  


Autosomal dominant

A trait determined by a gene on any chromosome other than a sex chromosome (X or Y) that requires only one gene for the trait to be expressed. The chance of passing the trait to an offspring is at least 50% for each pregnancy.
 See Diagram


Autosomal recessive

A trait determined by a gene on any chromosome other than a sex chromosome (X or Y) that requires two genes for the trait to be expressed. A person with only one copy of the gene is said to be a carrier for the trait.
 See Diagram

 


REFERENCES

American College of Obstetricians and Gynecologists. Antepartum Fetal Surveillance. Practice Bulletin no. 9. Washington, D.C. ACOG, 1999.

Cunningham FG. ed Williams Obstetrics, 22nd ed.,  New York: McGraw-Hill.2005

Gabbe ed: Obstetrics - Normal and Problem Pregnancies, 4th ed New York, NY, Churchill Livingstone; 2002

Jones, K.L. ed. Smith’s recognizable patterns of human malformation (5th ed.). Philadelphia: W.B. Saunders.1997

Resnik R, ed., Maternal-Fetal Medicine, 5th ed., pp. 859–899. Philadelphia: Saunders.

Stenchever MA, Droegemueller W, eds. Comprehensive Gynecology. 4th ed. St. Louis: Mosby, 2001

Woodward PJ ed. Diagnostic Imaging Obstetrics, 1st ed., Manitoba: Amirsys, 2005

Ogueh O, et al., Obstetric implications of low-lying placentas diagnosed in the second trimester.
Int J Gynaecol Obstet. 2003 Oct;83(1):11-7. PMID: 14511867


 


 

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