Glossary of Terms

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Cervical Mucus

Cervical mucus is secreted by glandular cells that are present in the cervix. This mucus protects the uterus from invasion by bacteria present in the vagina. It also plays an important role in infertility. The cervical mucus, in response to the estrogen hormone, becomes thin and elastic at the time of ovulation. This allows the sperm to travel through the cervix and the uterus to reach the egg in the fallopian tube. It also helps the sperm to stay alive in the cervix for a longer period of time.  A thick and dense mucus could prevent the passage of sperm through the cervix.

Cervical Stenosis

Narrowing of the cervical canal in such a way that menstrual flow can partially or completely be impeded. It is often the result of cervical injury due to surgery such as cone biopsy done for an abnormal Pap smear. It can cause infertility by hampering the normal passage of sperm through the cervix, and can often be treated by intrauterine insemination that bypasses the cervix altogether.


The part of the uterus that opens into the vagina. It is the segment that is checked for abnormal cells by a Pap smear. It is connected to the uterine cavity by a hollow canal called the cervical canal. The cervix secrets mucinous secretions (see Cervical Mucus) which play a major role in the transport of sperm in its journey towards the egg.


A GnRH Antagonist medication (see below) used in IVF to prevent ovulation prior to egg retrieval. 

Chemical Pregnancy

A pregnancy in its earliest stages that was detected by blood hormone levels but a gestational sac never developed.


A bacteria responsible for a sexually transmitted infection that can affect the tubes by causing permanent damage and thus infertility. Often occurs without significant symptoms. 


The nuclear structure of every living cell. Every human cell has normally 46 chromosomes. These chromosomes are made up of genes that govern all of the body's functions, and are also responsible for all the physical characteristics of an individual. Human gametes (i.e. eggs and sperm) contain only 23 chromosomes. When unified during fertilization, the total number of 46 chromosomes is thus restored. Abnormalities of chromosomes can result in miscarriages or congenital abnormalities. Age affects the quality of chromosomes in an egg and that is why infertility and miscarriages are more common in older women. For instance, the incidence of Down's Syndrome increases when a woman gets older. 

Clinical Pregnancy

A pregnancy that has advanced to a stage where a gestational sac and/or a fetus can be seen by ultrasound.

Clomiphene Citrate

Also known by the trade names of "Clomid" and "Serophene," it is a synthetic estrogen hormone that is commonly used for ovulation induction. It comes in 50 mg tablets that are taken by mouth once a day for 5 days in the early part of the menstrual cycle. Due to its anti estrogenic actions, some of its side effects include thickening of the cervical mucus and thinning of the endometrial lining. The former can interfere with normal passage of sperm through the cervix to reach the egg, and the latter with implantation.  Some women may complain of hot flashes (10%), nausea and/or breast discomfort (2-5%). Visual symptoms (blurring) rarely occur (<1.5%) but are an indication to discontinue therapy. 

Corpus Luteum

A follicle that releases an egg at the time of ovulation is subsequently called the corpus luteum. This is initially a partially collapsed cystic space that later can become a true cyst, and is very active in hormone secretion. Its major product is progesterone. If pregnancy does not occur, the corpus luteum "dies" roughly 10 to 14 days after ovulation. This leads to a sudden drop in progesterone levels, which in turn leads to menstruation. If, on the other hand, pregnancy occurs, the newly developing placenta secretes the HCG hormone, which salvages the corpus luteum and stimulates it to continue making progesterone. This placental support of the corpus luteum is indispensable for the first 7 weeks of pregnancy. From that point on, the placenta starts making its own progesterone and the corpus luteum is no longer needed. Therefore, it shrinks and becomes the "corpus albicans.”


The process of freezing sperm, eggs or embryos in extremely low temperatures (-196°C). This technique has been used for decades to freeze sperm. It allows us to quarantine the sperm while the donor is tested for transmittable infectious diseases. The sperm can then be thawed when necessary and used in artificial insemination. More recently, we have been able to freeze and preserve human embryos. This has enabled us to freeze and save embryos resulting from in vitro fertilization. These embryos can also be later thawed and transferred back to the uterus. This allows us to transfer fewer embryos at any one transfer, reducing the risks of high-order multiple births.

Cumulus Granulosa

A group of cells that surround the human egg. They are responsible for the nourishment of that egg. These cells secrete the hormone estrogen that causes the uterine lining to grow.

Cystic Fibrosis (CF)

The most common inherited single-gene mutation genetic disease in humans. Children with CF inherit a mutated copy of the gene CFTR from each parent. These children have serious lung and digestive problems that can lead to a shorter lifespan.