Deceleration

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

Deep vein thrombosis (DVT)

A blood clot in a blood vessel that carries blood back to the heart (vein). Symptoms include pain, tenderness, and swelling of the affected extremity.

Deep venous thrombosis most often occurs in the leg or pelvis, and has been reported to develop on the left side of the body more often than on the right side during pregnancy. Deep venous thrombosis is about ten times more likely to happen in women who are pregnant than in women of the same age who are not pregnant. Venous thrombosis has the highest chance of occurring during the first six weeks after birth.

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:

G3, P2

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 the neonatal period.

In expanded form the woman with triplets from the previous example would be described as G3, P1-1-1-4, indicating 3 pregnancies, 1 term delivery, 1 preterm delivery, 1 miscarriage or termination of pregnancy, and 4 living children.

Diabetes

A condition in which a person has an abnormally high amount of sugar (glucose) in their blood. Diabetes occurs when the body does not produce insulin, the hormone that lowers blood sugar, or when the cells in the body do not respond to insulin.

Overt diabetes may be diagnosed if any of the following criteria are present:

• Fasting* plasma glucose (FPG) ≥ 7.0 mmol/L (126 mg/dL).
• Hemoglobin A1C (A1C) is 6.5% or higher.
• Random plasma glucose ≥ 11.1 mmol/L (200 mg/dL) in a patient with symptoms of hyperglycemia or in hyperglycemic crisis (should be confirmed by FPG or A1C).
• 2-hour plasma glucose ≥ 11.1 mmol/L (200 mg/dL) during a 75 g OGTT as described by the WHO (results should be confirmed on repeat testing if hyperglycemia is equivocal).

*Fasting = no caloric intake for at least 8 hours.

Classification of diabetes

• Type 1 diabetes mellitus (T1DM) — Inability to produce insulin caused by autoimmune destruction of pancreatic β-cells. T1DM patients have a propensity to develop ketoacidosis. Previously termed insulin-dependent diabetes or juvenile diabetes.
• Type 2 diabetes mellitus (T2DM) — Insulin resistance in muscle and liver with β-cell failure leading to inadequate insulin secretion. Previously termed non-insulin-dependent diabetes.
• Other — Diabetes due to other specific causes such as cystic fibrosis or drug-induced (for example, glucocorticoids).
• Gestational diabetes mellitus (GDM) — Diabetes diagnosed in the second or third trimester of pregnancy that was not clearly overt diabetes prior to gestation or other types of diabetes occurring throughout pregnancy, such as type 1 diabetes..

Diabetic ketoacidosis (DKA)

Diagnostic criteria for diabetic ketoacidosis (DKA) [1]

Plasma glucose > 250 mg/dL*, arterial pH < 7.3, and positive serum and/or urine ketones (especially 3-β-hydroxybutyrate).

*DKA may occur with relatively low blood sugar levels during pregnancy.

Precipitating factors for diabetic ketoacidosis in pregnancy [2]

Protracted vomiting, starvation, use of β-sympathomimetic agents for tocolysis, infection, new-onset diabetes, poor control of blood sugars or poor compliance with treatment, insulin pump failure, steroid use for fetal lung maturation or chronic medical disorder.

Diamniotic

Two separate amniotic sacs (bags of water).

Diaphragm

The main 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 and 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 approximately 1 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 intellectual disability, 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 (for example, atrioventricular 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 about 1 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 about 90% of these cases the extra chromosome is inherited from the mother. The recurrence risk for this type of Down syndrome is approximately 1% overall and increases as the mother's age increases.

Extra material from chromosome 21 may also be inherited as a translocation in which the extra 21 chromosome is attached to another chromosome (often chromosome 14). This form of Down syndrome has a much higher recurrence rate ranging from 5 to 100% depending 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.

Findings on ultrasound examination that strongly suggest the diagnosis of Down syndrome include 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 and 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:

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