An exaggerated systemic response to ovarian stimulation characterized by a wide spectrum of clinical and laboratory manifestations. It may be classified as mild, moderate or severe according to the degree of abdominal distention, ovarian enlargement and respiratory, hemodynamic and metabolic complications.

A term generally used to indicate the number and/or quality of oocytes, reflecting the ability to reproduce. Ovarian reserve can be assessed by any of several means. They include: female age; number of antral follicles on ultrasound; anti-Mullerian hormone levels; follicle stimulating hormone and estradiol levels; clomiphene citrate challenge test; response to gonadotropin stimulation, and oocyte and/or embryo assessment during an ART procedure, based on number, morphology or genetic assessment of the oocytes and/or embryos.

Pharmacological treatment with the intention of inducing the development of ovarian follicles. It can be used for two purposes: 1) for timed intercourse or insemination; 2) in ART, to obtain multiple oocytes at follicular aspiration.

The process of slow-freezing or vitrification of tissue surgically excised from the ovary with the intention of preserving reproductive capacity.

Partial or complete rotation of the ovarian vascular pedicle that causes obstruction to ovarian blood flow, potentially leading to necrosis of ovarian tissue.

The natural process of expulsion of a mature egg from its ovarian follicle.

Pharmacological treatment of women with anovulation or oligo-ovulation with the intention of inducing normal ovulatory cycles.

The process by which an oocyte is activated to undergo development in the absence of fertilization.

The product of an oocyte that has undergone activation in the absence of the paternal genome, with (induced) or without (spontaneous) a purposeful intervention.

A surgical procedure in which a needle is introduced percutaneously into the epididymis with the intention of obtaining sperm.

Fetal or neonatal death occurring during late pregnancy (at 22 completed weeks of gestational age and later), during childbirth, or up to seven completed days after birth.

The number of perinatal deaths per 1000 total births (stillbirths plus live births).

The estimated average number of live born children per woman that would be born to a cohort of women throughout their reproductive years, if the fertility rates by age in a given period remained constant at the current age-specific fertility rate.

The space between the cytoplasmic membrane enclosing the oocyte and the innermost layer of the zona pellucida. (This space may contain the first and second polar bodies and extracellular fragments.)

A medical or pharmacological method to prevent the release of gonadotropins (FSH, LH) from the pituitary gland.

The small bodies containing chromosomes segregated from the oocyte by asymmetric division during telophase. The first polar body is extruded at telophase I and normally contains only chromosomes with duplicated chromatids (2c); the second polar body is extruded in response to fertilization or in response to parthenogenetic activation and normally contains chromosomes comprising single chromatids (1c).

An ovary with at least 12 follicles measuring 2–9 mm in diameter in at least one ovary (Rotterdam criteria). PCO may be present in women with PCOS, but also in women with normal ovulatory function and normal fertility.

A heterogeneous condition, which requires the presence of two of the following three criteria: (1) Oligo-ovulation or anovulation; (2) Hyperandrogenism (clinical evidence of hirsutism, acne, alopecia and/or biochemical hyperandrogenemia); (3) Polycystic ovaries, as assessed by ultrasound scan with more than 24 total antral follicles (2–9 mm in size) in both ovaries.

The condition in which a cell has more than two haploid sets of chromosomes: e.g. a triploid embryo has three sets of chromosomes and a tetraploid embryo has four sets. Polyploidy in a human embryo is not compatible with life.

The process by which an oocyte is penetrated by more than one spermatozoon.