A Reproductive Lexicon


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Implantation refers to the process that occurs when a blastocyst attaches to the uterine wall. The optimal implantation site is at the top of the uterus, in humans. If implantation occurs outside of the uterus, it is called an ectopic pregnancy and is not usually viable.

Imprinting is a mechanism that involves the placement of methyl groups onto DNA to prevent expression of one copy of a gene, either from the mother or from the father. Syndromes such as Beckwith-Wiedemann, Silver-Russell, Angelman, and Prader-Willi are associated with errors in imprinting.

in situ is a term used as an intermediate between in vivo and in vitro. For example, examining cells within an organ removed from the body would be an in situ experiment, as the organ has been removed from its native environment (the body), but the cells are being studied in the context of their usual place within the organ.

in vitro refers to occurrences outside of a living organism. An in vitro experiment is one that is completed outside of a living organism, in an artificial environment.

in vitro fertilization (IVF) is an assisted reproductive technology procedure in which eggs are combined with sperm outside of the body, so that fertilization can occur. The embryos that are created can then be implanted back into a woman’s uterus or frozen (cryopreserved) for future use.

in vivo refers to occurrences inside of a living organism. An in vivo experiment is one that is completed inside of a living organism.

Incontinence is the inability to control urination or defecation.

Induced menopause is menopause caused earlier than expected due to the use of prescription drugs, treatments, or surgical removal of the ovaries. It is a common cause of concern among women facing a cancer diagnosis, as the life-saving treatments used to fight cancer, such as radiation and chemotherapy, can also lead to premature menopause.

Infertility is the inability to become pregnant after one full year of trying to conceive a child (or six months, if a woman is 35 years of age or older).

The fallopian tube is comprised of three sections. The infundibulum is the distal end of the tube closest to the ovary. It has finger-like projections called fimbrae that sweep the oocyte, which is released from the ovary after ovulation, to guide it into the fallopian tube.

A passage in the anterior part of the abdominal wall which connects the abdominal cavity to the external genitalia. Structures such as the testes migrate through this pathway to enter the male scrotum. 

Inhibin is a protein hormone made by the female ovaries and male testes and provides feedback messages to the anterior pituitary regarding the status of the reproductive tissues. In females, inhibin rises during follicle development and falls once a mature egg is released from the ovary. Inhibin blocks the hormone activin, and the loss of this hormone results in infertility or sterility.

The inner cell mass (ICM) is the part of the blastocyst that is fated to become the embryo, amnion, and yolk sac. In contrast, the trophectoderm cells of the blastocyst will contribute to extra-embryonic tissues, such as the placenta and umbilical cord. Cells of the ICM are pluripotent, meaning they can give rise to all the cell lineages (ectoderm, endoderm, and mesoderm) found in the body. The ICM is, thus, a source of embryonic stem cells.

A committee that reviews, approves, and oversees all the research at an institution that involves the participation of human subjects.

A term used to describe individuals whose reproductive organs or sex characteristics don’t match what is typically described as male or female. 

Intracytoplasmic sperm injection (ICSI) is an ART procedure in which a single sperm is microinjected directly into an egg to achieve fertilization. This procedure is primarily used in situations where the male patient has very few sperm.

The term intrauterine refers to occurrences within the uterus. However, since the uterus has a cavity that is accessible through the cervix, the term is often used to mean "within the uterine cavity." Thus, intrauterine development refers to development of the embryo within the uterus (both before and after implantation), while an intrauterine device (IUD) is a contraceptive device inserted into the uterine cavity. 

The Intrauterine Device (IUD) is a T-shaped device implanted into the uterus for the purpose of contraception by preventing sperm from reaching the egg. There are four different IUDs available in the United States. Three of them, Liletta, Mirena, and Skyla, release a small amount of progestin similarly to a birth control pill, which usually makes periods lighter. One of them, ParaGard, also known as ‘the copper T IUD’, is hormone free and lasts longer than the hormonal options, but can cause heavier periods. IUDs are more than 99% effective, but they do not prevent against STIs.

Intrauterine growth retardation (or restriction) (IUGR) is the term applied to the condition resulting in a baby that is born of low birth weight (<10th percentile). It generally results from insufficient placental support.

Intrauterine insemination (IUI) refers to the transfer of "washed" semen or sperm directly into the uterine cavity though a catheter. By bypassing the mucosal surface of the cervix, which acts as a barrier, it increases the chance of sperm reaching the uterine cavity and tubes. Intrauterine insemination is most often used when the male has reduced sperm count or motility.


The fallopian tube is comprised of three parts. The isthmus is the thick-walled portion of the fallopian tube that enters the body of the uterus at the cornua.