Terms Description
Assisted Reproductive Technology/Technique (ART) All treatments or procedures that include the in vitro handling of both human oocytes and sperm or of embryos for the purpose of establishing a pregnancy. This includes, but is not limited to, in vitro fertilization and embryo transfer, gamete intrafallopian transfer, zygote intrafallopian transfer, tubal embryo transfer, gamete and embryo cryopreservation, oocyte and embryo donation, and gestational surrogacy. ART does not include assisted insemination (artificial insemination) using sperm from either a woman’s partner or a sperm donor
Biochemical pregnancy (preclinical spontaneous abortion / miscarriage) A pregnancy diagnosed only by the detection of hCG in serum or urine and that does not develop into a clinical pregnancy.
Blastocyst An embryo (5 or 7 days after fertilization) with an inner cell mass, outer layer of trophectoderm, and a fluid-filled blastocele cavity.
Blastulation rate The blastulation rate is defined as the number of blastocysts from 2 pronuclei (2PN) zygotes
Blastocyst transfer A procedure that involve placement of blastoccyst stage embryo into women’s womb in attempt to achieve pregnancy.
Cancelled cycle An ART cycle in which ovarian stimulation or monitoring has been carried out with the intention to treat, but which did not proceed to follicular aspiration or, in the case of a thawed embryo, to embryo transfer.
Cleavage stage embryo The embryo that develop to Day 2 or Day 3 after fertilization. Cleavage stage embryos range from the 2-cell stage in Day 2 post fertilization to the compacted morula composed of 8–16 cells in Day 3 post fertilization.
Cleavage stage embryo transfer A procedure that involve placement of cleavage stage embryo into women’s womb in attempt to achieve pregnancy.
Clinical pregnancy A pregnancy diagnosed by ultrasonographic visualization of one or more gestational sacs or definitive clinical signs of pregnancy. It includes ectopic pregnancy. Note: Multiple gestational sacs are counted as one clinical pregnancy.
Clinical pregnancy rate The number of clinical pregnancies expressed per 100 initiated cycles, aspiration cycles, or embryo transfer cycles. Note: When clinical pregnancy rates are given, the denominator (initiated, aspirated, or embryo transfer cycles) must be specified.
Cycle In fertility treatment, cycle involve a series of events from the first day of menstruation to the Day before next menstruation start
Controlled ovarian stimulation (COS) for ART Pharmacologic treatment in which women are stimulated to induce the development of multiple ovarian follicles to obtain multiple oocytes at follicular aspiration.
Cryopreservation The freezing or vitrification and storage of gametes, zygotes, embryos, or gonadal tissue.
Delivery The complete expulsion or extraction from the mother of one or fetuses at least 20 completed weeks of gestational age
Ectopic pregnancy Pregnancy in which implantation takes place outside the uterine cavity.
Elective embryo transfer The transfer of one or more embryos, selected from a larger cohort of available embryos.
Elective single-embryo transfer (eSET) The transfer of one embryo, selected from a by larger cohort of available embryos.
Double embryo transfer (DET) The transfer of two embryo, selected from a by larger cohort of available embryos.
Embryo The product of the division of the zygote to the end of the embryonic stage, 8 weeks after fertilization. (This definition does not include either parthenotes—generated through parthenogenesis— nor products of somatic cell nuclear transfer).
Embryo transfer (ET) The procedure in which one or more embryos are placed in the uterus or fallopian tube.
Embryo transfer cycle An ART cycle in which one or more embryos are transferred into the uterus or fallopian tube.
Extremely low birth weight Birth weight less than 1,000 g.
Fertilization The penetration of the ovum by the spermatozoon and combination of their genetic material resulting in the formation of a zygote.
Fetal death (stillbirth) Death before the complete expulsion or extraction from its mother of a product of fertilization, at or after 20 completed weeks of gestational age. The death is indicated by the fact that, after such separation, the fetus does not breathe or show any other evidence of life, such as heart beat, umbilical cord pulsation, or definite movement of voluntary muscles
Fetus The product of fertilization from completion of embryonic development, at 8 completed weeks after fertilization, until abortion or birth.
Frozen-thawed embryo transfer cycle (FET) An ART procedure in which cycle monitoring is carried out with the intention of transfering frozen-thawed embryo(s). Note: An FET cycle is initiated when specific medication is provided or cycle monitoring is started with the intention to treat.
Frozen-thawed oocyte cycle An ART procedure in which cycle monitoring is carried out with the intention of fertilizing thawed oocytes and performing embryo transfer.
Hatching The process by which an embryo at the blastocyst stage separates from the zona pellucida.
Implantation The attachment and subsequent penetration by the zona-free blastocyst (usually in the endometrium) that starts 5 to 7 days after fertilization.
Implantation rate The number of gestational sacs observed divided by the number of embryos transferred.
In vitro fertilization (IVF) An ART procedure that involves extracorporeal fertilization.
Infertility (clinical definition) A disease of the reproductive system defined by the failure to achieve a clinical pregnancy after 12 months or more of regular unprotected sexual intercourse
Intracytoplasmic sperm injection (ICSI) A procedure in which a single spermatozoon is injected into the oocyte cytoplasm.
Live birth The complete expulsion or extraction from its mother of a product of fertilization, irrespective of the duration of the pregnancy, which, after such separation, breathes or shows any other evidence of life, such as heart beat, umbilical cord pulsation, or definite movement of voluntary muscles, irrespective of whether the umbilical cord has been cut or the placenta is attached.
Low birth weight Birth weight less than 2,500 g.
Micromanipulation A technology that allows micro-operative procedures to be performed on the spermatozoon, oocyte, zygote, or embryo
Ovarian hyperstimulation syndrome (OHSS) An exaggerated systemic response to ovarian stimulation characterized by a wide spectrum of clinical and laboratory manifestations. It is classified as mild, moderate, or severe according to the degree of abdominal distention, ovarian enlargement, and respiratory, hemodynamic, and metabolic complications.
Ovarian torsion Partial or complete rotation of the ovarian vascular pedicle that causes obstruction to ovarian blood flow, potentially leading to necrosis of ovarian tissue.
PESA Percutaneous epididymal sperm aspiration.
Severe ovarian hyperstimulation syndrome Severe OHSS is defined to occur when hospitalization is indicated. (See definition of ‘‘ovarian hyperstimulation syndrome.’’)
Spontaneous abortion / miscarriage The spontaneous loss of a clinical pregnancy before 20 completed weeks of gestational age (18 weeks after fertilization) or, if gestational age is unknown, the loss of an embryo/fetus of less than 400 g.
TESA Testicular sperm aspiration.
TESE Testicular sperm extraction.
Very low birth weight Birth weight less than 1,500 g.
Very preterm birth A live birth or stillbirth that takes place after 20 but before 32 completed weeks of gestational age.
Vitrification An ultra-rapid cryopreservation method that prevents ice formation within the suspension which is converted to a glass-like solid.
Zygote A diploid cell resulting from the fertilization of an oocyte by a spermatozoon, which subsequently divides to form an embryo.