Fertility Glossary

The glossary below is provided by the Division of Reproductive Health at the Centers for Disease Control and Prevention.



Adverse outcome

A pregnancy that does not result in a live birth. The adverse outcomes reported for ART procedures are miscarriages, induced abortions, and stillbirths.

American Society for Reproductive Medicine (ASRM)

Professional organization devoted to advancing knowledge and expertise in reproductive medicine and biology. Their affiliate organization, the Society for Assisted Reproductive Technology (SART), is composed of clinics and programs that provide ART.

ART (assisted reproductive technology)

All treatments or procedures that involve surgically removing eggs from a woman’s ovaries and combining the eggs with sperm to help a woman become pregnant. The types of ART are in vitro fertilization (IVF), gamete intrafallopian transfer (GIFT), and zygote intrafallopian transfer (ZIFT).

ART cycle

A process in which (1) an ART procedure is performed, (2) a woman has undergone ovarian stimulation or monitoring with the intent of having an ART procedure, or (3) frozen embryos have been thawed with the intent of transferring them to a woman. A cycle begins when a woman begins taking fertility drugs or having her ovaries monitored for follicle production.



An ART cycle in which ovarian stimulation was performed but was stopped before eggs were retrieved or, in the case of frozen embryo cycles, before embryos were transferred. Cycles are canceled for many reasons: eggs may not develop, the patient may become ill, or the patient may choose to stop treatment.


A cycle that uses more than one ART procedure. Combination cycles usually involve IVF plus either GIFT or ZIFT.


The practice of freezing extra embryos from a couple’s ART cycle for potential future use.


Diminished ovarian reserve

This diagnosis means that the ability of the ovary to produce eggs is reduced. Reasons include congenital, medical, or surgical causes or advanced age.

Donor egg cycle

An embryo is formed from the egg of one woman (the donor) and then transferred to another woman who is unable to use her own eggs (the recipient). The donor relinquishes all parental rights to any resulting offspring.

Donor embryo

An embryo that is donated by a couple who previously underwent ART treatment and had extra embryos available.



A pregnancy in which the fertilized egg implants in a location outside of the uterus–usually in the fallopian tube, the ovary, or the abdominal cavity. Ectopic pregnancy is a dangerous condition that must receive prompt medical treatment.


A female reproductive cell, also called an oocyte or ovum.


A procedure to collect the eggs contained in the ovarian follicles.


The transfer of retrieved eggs into a woman’s fallopian tubes through laparoscopy. This procedure is used only in GIFT.


An egg that has been fertilized by a sperm and has undergone one or more divisions.


Placement of embryos into a woman’s uterus through the cervix after IVF: in ZIFT, the embryos are placed in a woman’s fallopian tube.


A medical condition that involves the presence of tissue similar to the uterine lining in abnormal locations. This condition can affect both fertilization of the egg and embryo implantation.


Elective single-embryo transfer is a procedure in which one embryo, selected from a larger number of available embryos, is placed in the uterus or fallopian tube. The embryo selected for eSET might be from a previous IVF cycle (i.e., cryopreserved embryos [frozen]) or from the current fresh IVF cycle that yielded more than one embryo. The remaining embryos may be set aside for future use or cryopreservation.


fertility clinic success rate and certification act of 1992 (fcsrca)

Law passed by the United States Congress in 1992 requiring all clinics performing ART in the United States to annually report their success rate data to CDC.


The penetration of the egg by the sperm and the resulting combining of genetic material that develops into an embryo.


The unborn offspring from the eighth week after conception to the moment of birth.


A structure in the ovaries that contains a developing egg.

Fresh eggs, sperm, or embryos

Eggs, sperm, or embryos that have not been frozen. Fresh embryos, however, may have been conceived using either fresh or frozen sperm.

Frozen embryo cycle

An ART cycle in which frozen (cryopreserved) embryos are thawed and transferred to the woman.



A reproductive cell, either a sperm or an egg.

GIFT (gamete intrafallopian transfer)

An ART procedure that involves removing eggs from the woman’s ovary, combining them with sperm, and using a laparoscope to place the unfertilized eggs and sperm into the woman’s fallopian tube through small incisions in her abdomen.


The period of time from conception to birth.

Gestational carrier (also called a gestational surrogate)

A woman who gestates, or carries, an embryo that was formed from the egg of another woman. The gestational carrier usually has a contractual obligation to return the infant to its intended parents.

Gestational sac

A fluid-filled structure that develops within the uterus early in pregnancy. In a normal pregnancy, a gestational sac contains a developing fetus.


ICSI (intracytoplasmic sperm injection)

A procedure in which a single sperm is injected directly into an egg; this procedure is most commonly used to overcome male infertility problems.

Implantation rate

A measurement of ART success when the ART cycle results in an intrauterine clinical pregnancy, defined as the larger of either the number of maximum fetal hearts by ultrasound or maximum infants born, including live births and stillbirths, out of the total number of embryos transferred.

Induced or therapeutic abortion

A surgical or other medical procedure used to end a pregnancy.

IUI (intrauterine insemination)

A medical procedure that involves placing sperm into a woman’s uterus to facilitate fertilization. IUI is not considered an ART procedure because it does not involve the manipulation of eggs.

IVF (in vitro fertilization)

An ART procedure that involves removing eggs from a woman’s ovaries and fertilizing them outside her body. The resulting embryos are then transferred into the woman’s uterus through the cervix.



A surgical procedure in which a fiber-optic instrument (a laparoscope) is inserted through a small incision in the abdomen to view the inside of the pelvis.

Live birth

The delivery of one or more infants with any signs of life.


Male factor

Any cause of infertility due to low sperm count or problems with sperm function that makes it difficult for a sperm to fertilize an egg under normal conditions.

Miscarriage (also called spontaneous abortion)

A pregnancy ending in the spontaneous loss of the embryo or fetus before 20 weeks of gestation, or before 18 weeks from the date of transfer if the pregnancy was achieved using ART.

Multifetal pregnancy reduction

A procedure used to decrease the number of fetuses a woman carries and improve the chances that the remaining fetuses will develop into healthy infants. Multifetal reductions that occur naturally are referred to as spontaneous reductions.

Multiple factors, female only

A diagnostic category used when more than one female cause of infertility is diagnosed.

Multiple factors, female and male

A diagnostic category used when one or more female causes and male factor infertility are diagnosed.

Multiple-fetus pregnancy

A pregnancy with two or more fetuses, determined by the number of fetal hearts observed on an ultrasound performed early in pregnancy (usually in the first trimester).

Multiple-infant birth

A pregnancy that results in the birth of more than one infant.


NASS (National ART Surveillance System).

Web-based data collection system used by all ART clinics to report data for each ART procedure to CDC.



The female reproductive cell, also called an egg.

Other causes of infertility

These include immunological problems, chromosomal abnormalities, cancer chemotherapy, and serious illnesses.

Ovarian monitoring

The use of ultrasound and/or blood or urine tests to monitor follicle development and hormone production.

Ovarian stimulation

The use of drugs (oral or injected) to stimulate the ovaries to develop follicles and eggs.

Ovulatory dysfunction

A diagnostic category used when a woman’s ovaries are not producing eggs normally. It includes polycystic ovary syndrome and multiple ovarian cysts.


PGD (Preimplantation Genetic Diagnosis).

A technique combining the recent significant advances in molecular genetics and assisted reproductive technology. PGD allows physicians to identify various genetic diseases in the embryo (fertilized egg with several divisions) prior to implantation, that is, before the pregnancy is established. It is of special value for those who are at risk of having children with serious genetic problems.

Pregnancy (clinical)

A pregnancy documented by ultrasound that shows a gestational sac in the uterus. For ART data collection purposes, pregnancy is defined as a clinical pregnancy rather than a chemical pregnancy (i.e., a positive pregnancy test).



A single live-born infant.

Society for Assisted Reproductive Technology (SART)

An affiliate of the American Society for Reproductive Medicine composed of clinics and programs that provide ART.


The male reproductive cell.

Spontaneous abortion

See .


The birth of an infant that shows no sign of life after 20 or more weeks of gestation, or 18 or more weeks from the date of transfer if the pregnancy was achieved using ART.

Stimulated cycle

An ART cycle in which a woman receives oral or injected fertility drugs to stimulate her ovaries to produce more follicles.


Thawed embryo cycle

Same as frozen embryo cycle.

Tubal factor

A diagnostic category used when the woman’s fallopian tubes are blocked or damaged, making it difficult for the egg to be fertilized or for an embryo to travel to the uterus.



A technique used in ART for visualizing the follicles in the ovaries, the gestational sac, or the fetus.

Unexplained cause of infertility

A diagnostic category used when no cause of infertility is found in either the woman or the man.

Unstimulated cycle

An ART cycle in which the woman does not receive drugs to stimulate her ovaries to produce more follicles. Instead, follicles develop naturally.

Uterine factor

A structural or functional disorder of the uterus that results in reduced fertility.


ZIFT (zygote intrafallopian transfer)

An ART procedure in which eggs are collected from a woman’s ovary and fertilized outside her body. A laparoscope is then used to place the resulting zygote (fertilized egg) into the woman’s fallopian tube through a small incision in her abdomen.