A Reproductive Lexicon


Ownership of this website has been transferred from Northwestern University to Michigan State University.
Please note that some site information may be inaccurate while adjustments to reflect this organizational change are made.

MOOC Advertisement

Learn More:
Get An Introduction to Reproduction

Learn more about the science of reproduction. Dr. Teresa Woodruff, creator of Repropedia, is offering a free online course exploring the world of reproduction.

Get Started!


A common condition which occurs 3-5 days after childbirth that is characterized by mood swings, feelings of anxiety, difficulty sleeping and trouble eating. If these symptoms worsen, or persist beyond 5 days, patients may be experiencing postpartum depression. 

Bacterial vaginosis is a bacterial infection in the vagina that occurs when the balance of bacteria is upset. Symptoms include a grayish-yellow discharge and fishy smell. Douching, smoking, and having multiple sexual partners can increase a woman's risk of getting bacterial vaginosis. Women who are pregnant and get bacterial vaginosis may have a higher risk of miscarriage or pre-term labor.

The barrier method refers to birth control methods used during sexual intercourse that pose a physical barrier to sperm that would otherwise enter the uterus. These methods include a diaphragm, cervical cap, male or female condom, and spermicidal foam, sponges, and film. It is important to note that male and female condoms are the only birth control methods that may prevent the contraction of STIs.

The maternal side of the placenta.

A transcription factor that is part of the WNT4 signaling pathway, and is therefore involved in the development of the female reproductive tract.

Bioengineering (also referred to as biological engineering) is a field of science in which the principles of engineering are applied to biology and medicine. Often times, bioengineering is applied to human health in order to develop new technologies that model, modify, or control biological systems.

A bioethicist is a person who studies the moral and ethical issues that surround biological advances in science, technology, and medicine by drawing from other surrounding disciplines, including law, philosophy, and politics.

Bioethics is the study of ethical issues that arise due to advancements in biology, medicine, health care, health policy, and health science.

Bioidentical hormones are synthesized or artificial hormones that are structurally identical to hormones made within the body. Common bioidentical hormones include synthesized estrogen and progesterone, both often used in hormone therapy. Bioidentical hormones are often made using chemicals extracted from plants, and they are finely ground to make them more absorbent in the body.

Biomarkers are proteins or small molecules which can be measured in the blood, urine, or other bodily fluids in order to diagnose conditions, identify disease, track disease progression, and/or monitor therapeutic interventions.  

A biomaterial is any natural or synthetic material that is used for biological application. For example, the components of an artificial joint are biomaterials.

Birth refers to the process where an offspring is produced from the womb (in mammals).

A birth defect is any developmental abnormality present at birth that can be caused by a variety of factors, including drug and alcohol use by the mother during prenancy, exposure of the mother to pathogens during pregnancy, abnormalities in chromosome number, issues with gene expression, etc.

Bisphenol A (BPA) is an industrial chemical and endocrine disruptor that has been used to make certain plastics and resins since the 1960s. BPA remains controversial because of its potential to seep into foods or beverages kept in containers that are made with the compound. It also has the ability to seep into the body when handling products that contain the chemical. Studies with rodents have shown that exposure to BPA can interfere with reproductive function.

Bisphosphonates are drugs that can slow or stop the activity of bone-dissolving cells and preserve bone density, bone strength, and reduce the risk of fracture. Bisphosphonates are commonly used to prevent and treat osteoporosis, especially in post-menopausal women who have the disease.

Black cohosh is an herbal supplement that is used to treat the symptoms of menopause, such as hot flashes, mood disturbances, and vaginal dryness. It is also sometimes used to treat the symptoms of menstruation, premenstrual syndrome, and to induce labor in pregnant women. Research is inconclusive as to its effectiveness.

A blastocoel is the fluid-filled cavity of the blastula.

A blastocyst is an early embryo that is less than a week old, usually forming five days after fertilization from the morula in the uterus and implanting into the uterine wall six days after fertilization. Blastocysts are composed of two distinct cell lineages: the inner cell mass (ICM) that will become the embryo and the trophoblast that will become the placenta. The trophoblast surrounds the ICM and the inner, fluid-filled cavity called the blastocoel.

A blastomere is a single cell of a pre-implantation stage embryo formed by cell division of the zygote following fertilization. Using the specific assisted reproductive technology known as preimplantation genetic diagnosis, a single blastomere is removed from an embryo, and genetic testing is performed on this cell, so that embryos free of genetic abnormalities are transferred back into the recipient.

Blastulation is the formation of the blastula and blastocoel following the morula stage of embryo development. 


Bone mineral density refers to the amount of calcium and other minerals that exist in a segment of bone. A bone mineral density test is used to assess bone strength, predict the risk of fracture, and can be used to diagnose osteoporosis (a common ailment in post-menopausal women).


Braxton Hicks contractions, also known as practice contractions or false labor pains, are irregular uterine contractions that may begin as early as the second trimester of pregnancy but are more commonly felt during the third trimester. These contractions are usually experienced as an uncomfortable cramping sensation in the lower abdomen. They do not lead to the onset of labor and usually disappear with rest. Braxton Hicks contractions are acknowledged as the body’s way of preparing for the birthing process. The term “Braxton Hicks” dates back to the first description of these contractions by an English doctor named John Braxton Hicks in 1872.

The breast is the tissue located on the right and left sides of the front of the chest and contains the mammary glands. The mammary glands secrete milk for the purpose of feeding an infant, and they are sensitive to ovarian hormones and prolactin.

A breech birth is the birth of a baby from a breech presentation, which refers to the baby exiting the pelvis feet or buttocks first. It accounts for about 3-4 % of all singleton deliveries. Factors associated with breech birth include high parity with uterine relaxation, twin or multiple fetuses, preterm labor, changes in amniotic fluid volume (poly- or oligo-hydramnios), previous breech birth, placental anomalies (placenta previa or fundal placental implantation), fetal head anomalies (hydrocephaly or anencephaly), uterine anomalies, and pelvic tumors. Generally, a baby in the breech position will be delivered by Caesarean section, as vaginal delivery is associated with high risks to the life of the mother and child.

Breech presentation refers to the positioning of the baby inside the mother’s womb, where the buttocks and/or legs occupy the lower section of the uterus, while the baby's head occupies the upper section of the uterus. Types of breech presentation include: Frank Breech 65%, Complete Breech 10%, and Incomplete Breech 25 % (Footling and Kneeling). Frank Breech is when the baby's hip joints are flexed and knee joints are extended. Complete Breech is when the baby's hip and knee joints are flexed. Footling Breech is when the baby's hip and knee joints are extended. Kneeling Breech is when the baby's hip joints are extended and knee joints are flexed.

The fold of peritoneum that connect certain components of the female reproductive tract to the walls and floor of the pelvis. The broad ligament can be divided into three parts: the mesovarium which supports the ovaries, the mesometrium which supports the uterus, and the mesosalpinx which supports the fallopian tubes. 

The two bulbourethral glands (also known as Cowper's glands) are accessory glands of the male reproductive tract located on either side of the prostate gland. They produce secretions that become a component of semen during ejaculation.