Glossary B

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Glossary B
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Bag of waters

The membrane (amnion) surrounding the fetus and the amniotic fluid.

Banana Sign
Curvature of the cerebellum (the part of the brain that controls balance) around the midbrain giving the cerebellum the shape of a banana. Caused by Arnold-Chiari II malformation. In 95% percent of cases the Arnold-Chiari II malformation is accompanied by hydrocephalus and myelomeningocele (open spina bifida).

Bicornuate uterus

Two separate single horn uterine bodies sharing one cervix.

The uterine tubes, uterus, and upper vagina are formed by fusion of the two paramesonephric (Müllerian) ducts beginning at about 10 weeks gestation. Fusion of the ducts with resorption of the uterine septum is usually completed by about 20 weeks' . Partial failure of the ducts to unite results in two separate single horn uterine bodies sharing one cervix.
Bicornuate uterus is associated with increased risk for miscarriage, preterm labor, breech presentation, and fetal growth restriction.

Bilirubin

Bilirubin is a yellowish pigment produced from the breakdown of hemoglobin the protein that carries oxygen in the red blood cells). Bilirubin is removed from the body largely by the liver. The liver of many newborns may not be mature enough to remove bilirubin from the blood stream quickly enough. The excess bilirubin may build up giving the the infant's skin and membranes a yellow color a condition called jaundice.

Biophysical profile (BPP)

Biparietal diameter (BPD)
The distance between the parietal eminences on each side of the skull.

The distance is measured by sonogram from the outer surface of the skull to the opposite inner surface of the skull.

The appropriate transverse plane for measurement of the fetal biparietal diameter (BPD) and head circumference (HC) should include the thalamic nuclei (structures deep in the brain) and the cavum septum pellucidum (a space between the thin membranes that separate the lateral ventricles). Both structures are inferior to the corpus callosum

T = Thalamus C= Cavum septum pellucidum

Bishop score

An assessment of the likelihood of successful induction of labor. The Bishop score assigns points for cervical dilatation, effacement, consistency, cervical position, and the station of the presenting part. A Bishop's score of less than 5 indicates low probability of successful induction. Other scoring systems exist.

SCORE

CERVICAL EXAM
0 1 2 3

Dilation (cm)
Closed

1-2 cm

3-4cm

>5cm

Effacement (%)
0-30%

40-50%

60-70%

>80%

Consistency
Firm

Medium

Soft

Position Posterior Mid Anterior

Station
-3

-2

-1

+1, +2

Blastocyst

The rapidly dividing fertilized egg when it enters the uterus

Bloody show

Passage of blood-tinged mucus from the vagina caused by loss of the cervical mucous plug. Bloody show often precedes the onset of labor.

Bowel

Brachycephaly

Short disproportionately wide head. Brachycephaly is seen with several disorders including Down syndrome and syndromes associated with premature closure of the coronal suture (Apert, Crouzon, Pfeiffer, Saethre-Chotzen and Carpenters).

Bradycardia

In a fetus a mean heart rate less than 110 beats per minute lasting for at least two minutes. In an adult a sustained heart rate less than 60 beats per minute.

Braxton Hicks contractions

Sporadic uterine contraction that do not increase in intensity and do not result in childbirth. Named after John Braxton Hicks a British gynecologist who first described these contractions in 1872.

Breech presentation

The fetus is in a sitting position with the buttocks, knees, or feet nearest to the cervix.
Breech presentation occurs in 25 percent of pregnancies less than 28 weeks' and 1 to 3 percent of births at term. The three types of breech presentation are frank breech (flexed at hips with extended knees-legs above buttocks), footling breech (one or both hips extended-leg(s) extended below buttocks), and complete breech (flexed hips and knees-no limbs extended).