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Deceleration

A decrease in the fetal heart rate below the baseline heart rate lasting at least 15 seconds.


Detailed Obstetric Notation

In an obstetrical history the gravida (G) and para (P) status of a woman is often written in abbreviated form. Where:

    Gravida is the number of pregnancies a woman has had. A multiple gestation counts as a single pregnancy.

    Para is the number of completed pregnancies beyond 20 weeks gestation (whether viable or nonviable). A multiple gestation counts as a single birth.

For example a woman who has been pregnant 3 times (where one pregnancy was a set of triplets) has one term delivery, one preterm delivery (of her triplets), and one termination at 16 weeks would be described as:

G 3,P 2

 

Expanded obstetric notation gives more detail:

G, T-P-A-L =

 Gravida (Total number of pregnancies), Term births -Preterm births - Abortions - Living children

Where :

    Term births means delivery at 37 or greater weeks' gestation.

    Preterm birth means delivery at 20 to  36 6/7 weeks' gestation

    Abortion is delivery before 20 weeks' gestation.

    Living children means children who lived beyond neonatal period.

In expanded form the woman with triplets  from the previous example would be described as  G 3, P 1- 1- 1- 4 indicating 3 pregnancies, 1 term delivery, 1 preterm delivery, 1 miscarriage or termination of pregnancy, and 4 living children.


Diamniotic

Two separate amniotic sacs (bags of water)


Diaphragm

The muscle used for breathing . It divides the chest from the abdomen.


Diaphragmatic hernia (congenital diaphragmatic hernia -CDH)

An abnormal opening in the diaphragm (most often on the left side) caused by failure to completely form the diaphragm. The defect allows the abdominal organs to move into the chest cavity which may prevent normal development of the lungs. The condition is associated  with a 30 to 60% death rate due to underdeveloped lungs and associated abnormalities such as heart defects, malformed or absent kidneys, and hydrocephalus. The presence of the liver in the chest generally increases the likelihood of a poor outcome.

Diaphragmatic hernia occurs in one per 2,000 to 3,000 births. Chromosome abnormalities are seen in up to 15% of fetuses with diaphragmatic hernia. The most common chromosome abnormalities are trisomy 18, and trisomy 21. The defect has also been reported in association with multiple syndromes including Fryn and Cornelia de Lange syndromes.

Congenital diaphragmatic hernia may be diagnosed prenatally on ultrasound. The usual finding is a heart displaced away from the side of the hernia and the presence of the stomach in the chest at the level of the heart.


Dichorionic

Two separate placentas.


Dilation and curettage (D and C)

A surgical procedure in which the cervix is gradually opened with instruments called dilators and the surface of the endometrium (lining of the uterus) is scraped away with a curette, a sharp-edged instrument.


Dizygotic twins (fraternal twins)

A twin pregnancy most commonly occurs when two separate eggs are fertilized by separate sperm to form two zygotes. Each zygote implants in the uterus individually and develops its own membranes and placenta.  The two zygotes continue to develop as two separate embryos. These twins are referred to as dizygotic (commonly known as fraternal) twins. Fraternal twins account for about 70 % of naturally occurring  twins in the United States .


Down syndrome (trisomy 21)

A disorder characterized by mental retardation, flat facial profile with protruding tongue, poor muscle tone, excess skin on neck, slanting eye openings (slanted palpebral fissures), abnormal pelvis, and short stature. In addition there may be heart defects (AV canal defect) , gastrointestinal malformations, problems with vision and hearing, and  increased susceptibility to leukemia and infections. The syndrome is named after John Langdon Down, the first physician to identify the syndrome.

Down syndrome occurs in one out of 800 live births and is caused by extra material from chromosome 21. In most cases (95%) there are three copies of chromosome 21 instead of two. In 90% of these cases the extra chromosome is inherited from the mother. The recurrence risk for this type of Down syndrome is 1% overall and increases the mother's age increases. Extra material from chromosome 21 may also be inherited as a translocation where the extra 21 chromosome is attached on to another chromosome (often chromosome 14). This form of Down syndrome has a much higher recurrence rate ranging from 5 to 100% depending on on the sex of the carrier parent and  the type of chromosome rearrangement. Uncommonly a child may be born with mosaic Down syndrome where some of the child's cells have three copies of chromosome 21 and some cells have the normal two copies of chromosome 21.

Findings on ultrasound examination that strongly suggest the diagnosis of Down syndrome are an atrioventricular (AV) canal defect in the heart or duodenal atresia (double bubble sign). An increased nuchal translucency or nuchal fold (the space in the back of a developing fetus's neck) may also suggest Down syndrome. However, none of the above findings is exclusive to Down syndrome and, ultimately,  Down syndrome is diagnosed by analyzing cells from the fetus.


Due date (estimated due date-EDD)

The date that spontaneous onset of labor is expected to occur.


Dystocia

Slow or difficult labor caused by inadequate uterine contractions, abnormalities in the maternal pelvis, a large fetus or a combination of these causes.


Doppler ultrasound

A method using ultrasound to detect and measure blood flow.

The ultrasound machine emits sound waves into the body then measures the frequency of the sound waves returning from moving blood cells to determine the speed (velocity) of blood flow. As cells approach the ultrasound transducer reflected sound waves are compressed  resulting in a higher frequency sound.  As cells travel away from the transducer the reflected waves are elongated resulting in a lower frequency sound. This change in frequency (pitch of the sound) is due to the motion of the reflecting cells and is called The Doppler Effect or Doppler shift.

Blood velocities can be calculated from the change in frequency of the reflected ultrasound:
 

fD X C
  v =
  2 f0X cos(α)

Where v is the blood velocity, c is the sound velocity in tissue, f0 is the transmitted frequency, fD is the Doppler shift of reflected ultrasound and α is the angle between the ultrasound beam and the direction of motion.



 

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