A membrane-bound structure covering the anterior of the sperm head that contains enzymes necessary to penetrate the zona pellucida of the oocyte.

A form of endometriosis marked by the presence of endometrium-like epithelium and stroma outside the endometrium in the myometrium.

Bands of fibrous scar tissue that may bind the abdominal and pelvic organs, including the intestines and peritoneum, to each other. They can be dense and thick or filmy and thin.

The number of live births per woman in a particular age group in a specific calendar year expressed per 1000 women in that age group.

Clumping of spermatozoa in the ejaculate.

The medical practice dealing with the health of the male reproductive system.

An abnormal number of chromosomes in a cell. The majority of embryos with aneuploidies are not compatible with life.

Antibodies that recognize and bind to antigens on the surface of the spermatozoon.

Lack of external ejaculation.

An ART procedure in which the zona pellucida of an embryo is either thinned or perforated by chemical, mechanical or laser methods.

All interventions that include the in vitro handling of both human oocytes and sperm or of embryos for the purpose of reproduction. This includes, but is not limited to, IVF and embryo transfer ET, intracytoplasmic sperm injection ICSI, embryo biopsy, preimplantation genetic testing PGT, assisted hatching, gamete intrafallopian transfer GIFT, zygote intrafallopian transfer, gamete and embryo cryopreservation, semen, oocyte and embryo donation, and gestational carrier cycles. Thus, ART does not, and ART-only registries do not, include assisted insemination using sperm from either a woman’s partner or a sperm donor. (See broader term, medically assisted reproduction, MAR.)

Reduced percentages of motile and morphologically normal sperm in the ejaculate below the lower reference limit. When reporting results, the reference criteria should be specified.

Reduced percentage of motile sperm in the ejaculate below the lower reference limit. When reporting results, the reference criteria should be specified.

The absence of spermatozoa in the ejaculate.

The presence of two nuclei in a blastomere (cell).

A pregnancy diagnosed only by the detection of beta hCG in serum or urine.

The complete expulsion or extraction from a woman of a fetus after 22 completed weeks of gestational age, irrespective of whether it is a live birth or stillbirth, or, if gestational age is unknown, a birth weight more than 500 grams. A single birth refers to an individual newborn; and a delivery of multiple births, such as a twin delivery, would be registered as two births.

Fluid-filled central region of the blastocyst.

The stage of preimplantation embryo development that occurs around day 5–6 after insemination or ICSI. The blastocyst contains a fluid filled central cavity (blastocoele), an outer layer of cells (trophectoderm) and an inner group of cells (inner cell mass).

A cell in a cleavage stage embryo.