Back Labor

Labor pains which are felt through the lower back.

Bag of Waters

The thin walled sac inside the uterus that surrounds the baby, amniotic fluid and the placenta during pregnancy. It has a capacity of about 4 to 5 liters at term.

The wall of the sac is made up from the amnion, chorion and decidua, each of which are just a few cell layers thick, and which extends from the margin of the placenta. While each of the layers are in contact, they are not fused together.

The sac serves to maintain the equilibration hydrostactic pressure withing the uterus during pregnancy. During labor the sac transmits uniform pressure of the uterine contractions to the cervix for dilation.

Barbiturates

A powerful and highly addictive drug which is a derivative of barbituric acid that acts as a sedative or hypnotic.

Bearing Down

The motion made by the uterus as it pushes during the second stage of labor.

Beta-andrenergics

Beta-andrenergics are agents designed to affect the nervous system and inhibit transmission of stimuli. In pregnancy they are used to stop labor.

Bile Pigment

The broken down red blood cells converted into non-toxic substances in the liver from the hemoglobin. Newborns may have levels of pigment too high for the liver to convert. Also known as bilirubin.

Bilirubin

The broken down red blood cells converted into non-toxic substances in the liver from the hemoglobin. Newborns may have levels of pigment too high for the liver to convert. Also known as bile pigment.

Biophysical Profile

A test used to evaluate a baby before birth.

Biopsy

The removal of a piece of living tissue from a part of the body for microscopic study to confirm or establish a diagnosis, estimate prognosis or follow the course of a disease.

Birth Canal

The passage through which the baby passes during delivery from the inlet of the true pelvis to the vaginal orifice.

Birth Defect

Any abnormality which is present at birth. Also called congenital abnormalities, they can arise from genetic inheritance or acquired during gestation through disease or drugs.

Birthing Center

A facility in which you can go into labor and deliver a baby. The birthing center may or may not be part of a hospital and is staffed primarily by midwives.

Blastocyst

The embryonic stage of development following the morula during the early stages of pregnancy. Spherical in shape, it consists of a mass of two layers of cells surrounding a fluid filled cavity, the blastocoele. The outer layer of cells, the trophoblast will develop to form the placenta, while the inner layer, the embryoblast, will become the fetus. The blastocyst usually implants itself in the wall of the uterus on the eighth day following fertilization. It is also known as the blastula.

Blastula

The embryonic stage of development following the morula during the early stages of pregnancy. Spherical in shape, it consists of a mass of two layers of cells surrounding a fluid filled cavity, the blastocoele. The outer layer of cells, the trophoblast will develop to form the placenta, while the inner layer, the embryoblast, will become the fetus. The blastula usually implants itself in the wall of the uterus on the eighth day following fertilization. It is also known as the blastocyst.

Blighted Ovum

A description of the fertilized egg which fails to develop. It appears as a fluid filled cell attached to the uterus when viewed through x-ray or ultrasound. A blighted ovum results in many first trimester spontaneous abortions.

Blood Clot

An abnormal condition of the veins in which a blockage occurs due to the aggregation of platelets, fibrin and cellular elements of the blood attaching to the interior walls of a vein or artery. Also called thrombosis.

Blood Group

A system whereby different types of blood are classified according to the presence or absence of antigens on the red blood cells. Understanding a patient's blood group is important in pregnancy to prevent rhesus disease, and in blood transfusion therapy. There are over fourteen different types of blood grouping methods, the most common of which is the ABO method.

The ABO blood group is identified by the presence of two different types of antigens (labeled A and B) on the surface of the red blood cell. Using this method, four different types of blood classification is possible: A for Type A antigens, B for Type B antigens, AB if both are present, and O if neither are present.

The plasma of patients with Type-O blood contains the antibodies anti-A and anti-B agglutinins. Patients with Type-A blood do not have the anti-A agglutinins, and those with Type-B blood have an absense of anti-B agglutinins in the plasma. Blood grouping also notes the rhesus factor in the blood. See also Rhesus Factor, rh-negative and rh-sensitivity.

Bloody Show

A small amount of vaginal bleeding that occurs early in labor and frequently at the time of full dilation of the cervix at the end of the first stage of labor.

Board Certification

Specialized training and examination of medical staff in a particular area of medicine. For obstetrics, board certification training is offered by the American Board of Obstetrics and Gynecologists and required expertise in care of pregnant women.

Bradycardia

An abnormally slow heartbeat of below 120 beats per minute in the fetus or newborn baby.

Braxton Hicks Contractions

Irregular contractions of the uterus that begins during the first trimester and increases in frequency and intensity throughout pregnancy in reheasal for labor.

When the pregnancy is near term, Braxton Hicks contractions are hard to distinguish from true labor.

Breaking of the Waters

Rupturing of the amniotic sac releasing the amniotic fluid. It is usually one of the first signs of the onset of labor. Also called Rupture of the membranes.

Breast Pump

A mechanical device designed to draw breast milk from the mother's breasts.

Breech Presentation

The position of the baby within the uterus when the feet or buttocks are down and will appear first if delivered. Breech presentations make up about 3% of all labor and consist of complete breech, footling breech and frank breech. Read the Guide to Labor and Delivery for more information.

Brow Presentation

The position of the baby within the uterus when the head is down, but the chin is high so that the brow will emerge through the cervix first.