Glossary of Terms

Index

A–D

ART (assisted reproductive technology). All treatments or procedures that include the handling of human eggs or embryos to help achieve a pregnancy. The most common type of ART is in vitro fertilization (IVF). Other types of ART, such as gamete intrafallopian transfer or zygote intrafallopian transfer, are rarely performed. ART also includes egg and embryo cryopreservation (freezing) and egg and embryo donation. An ART procedure is sometimes referred to as a cycle of treatment or an ART cycle.

Clinical pregnancy. A pregnancy documented by ultrasound that shows a gestational sac (fluid-filled structure that develops early in pregnancy surrounding the embryo) in the uterus. For ART data-reporting purposes, pregnancy is defined as a clinical pregnancy rather than a chemical pregnancy (positive pregnancy test).

Cryopreservation. The practice of freezing eggs or embryos from a patient'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.

Donor egg cycle. An ART cycle where an embryo is formed from the egg of one woman (the donor) and then transferred to another woman (the recipient). Sperm from either the recipient's partner or a donor may be used.

Donated embryo cycle. An ART cycle where an embryo is donated by a patient or couple who previously underwent ART treatment and had extra embryos available and then transferred to another woman (the recipient).

E–G

Ectopic pregnancy. A pregnancy where 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 requires prompt medical treatment.

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

Egg or Embryo banking cycle. An ART cycle started with the intent of freezing (cryopreserving) all resulting eggs or embryos for potential future use. This may include freezing with the intent for future use in the short term (≤12 months) or long term (>12 months). Long-term egg or embryo banking is also called fertility preservation.

Egg retrieval (also called oocyte retrieval). A procedure to collect the eggs contained in the ovarian follicles.

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

Embryo transfer. Placement of embryos into a woman's uterus through the cervix after IVF.

Endometriosis. A medical condition that involves the presence of tissue similar to the uterine lining in locations outside the uterus, such as the ovaries, fallopian tubes, or abdominal cavity.

Fertility preservation cycle. An ART cycle started with the intent of freezing and banking all eggs or embryos for more than 12 months for future use.

Fertilization. The penetration of the egg by the sperm and the resulting combination of genetic material that may develop into an embryo.

Follicle. 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 embryo cycle. An ART cycle where fresh (never frozen) embryos are transferred to the woman. Fresh or frozen eggs may be combined with fresh or frozen sperm to create fresh embryos.

Frozen embryo cycle. An ART cycle where frozen (cryopreserved) embryos are thawed and transferred to the woman. Fresh or frozen eggs may be combined with fresh or frozen sperm to create frozen embryos.

Gestational age. The time from estimated last menstrual period (LMP) to birth. LMP for ART cycles is estimated using the date of retrieval or transfer.

Gestational carrier (also called a gestational surrogate). A woman who gestates, or carries, an embryo that was formed from the egg of another woman with the expectation of returning the infant to its intended parents.

GIFT (gamete intrafallopian transfer). An ART procedure that involves removing eggs from the woman's ovary and using a laparoscope to place the unfertilized gametes (eggs and sperm) into the woman's fallopian tube through small incisions in her abdomen.

I–L

ICSI (intracytoplasmic sperm injection). A procedure where a single sperm is injected directly into an egg; this procedure is commonly used to treat male infertility.

Implantation rate. When the ART cycle results in an intrauterine clinical pregnancy, the implantation rate is defined as the larger of either the maximum number of fetal hearts detected by ultrasound or the maximum number of infants born, including live-birth deliveries and stillbirths, out of the total number of embryos transferred.

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 a woman's uterus through the cervix. IVF is the most common type of ART.

Live-birth delivery. The delivery of one or more infants with at least one born alive.

M–P

Male infertility or male factor infertility. 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.

Multiple live-birth delivery. The delivery of more than one infant with at least one born alive.

Oocyte. The female reproductive cell, also called an egg or ovum.

Other reason, infertility. Reason for using ART that is related to infertility; may include immunological problems, chromosomal abnormalities, cancer chemotherapy, and serious illnesses.

Other reason, non-infertility. Reason for using ART that is not related to infertility.

Ovarian hyperstimulation syndrome. A complication of ovarian stimulation that can cause enlarged ovaries, a distended abdomen, nausea, vomiting or diarrhea, fluid in the abdominal cavity or chest, breathing difficulties, changes in blood volume or viscosity, and diminished kidney perfusion and function.

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 is usually characterized by irregular menstrual cycles with ovaries that are not producing one mature egg each month. It includes polycystic ovary syndrome (PCOS) and multiple ovarian cysts.

Patient (nondonor) cycle. An ART cycle where an embryo is formed from the egg of the patient and either partner or donor sperm and then transferred back to the patient.

PGT (preimplantation genetic testing). Diagnostic or screening techniques performed on embryos before transfer to (1) detect specific genetic conditions to reduce the risk of passing inherited diseases to children or (2) screen for an abnormal number of chromosomes, which is more frequent for patients with advanced age, recurrent miscarriages, or prior failed IVF.

S–T

SET (single embryo transfer). A procedure where one embryo, regardless of how many embryos are available, is transferred. The embryo selected for SET might be a frozen (cryopreserved) embryo from a previous IVF cycle or a fresh embryo from the current fresh IVF cycle.

Singleton live-birth delivery. The delivery of a single infant born alive. Singleton live-birth delivery does not include the delivery of more than one infant with only one born alive.

Sperm. The male reproductive cell.

Spontaneous abortion. See Miscarriage.

Stillbirth. A fetal death in the uterus after 20 weeks of pregnancy.

Stimulated cycle. An ART cycle where a woman receives oral or injected fertility drugs to stimulate her ovaries to develop follicles that contain mature eggs.

Tubal factor infertility. 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.

U–Z

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

Unstimulated cycle. An ART cycle where the woman does not receive drugs to stimulate her ovaries to produce more follicles and eggs. Instead, follicles and eggs develop naturally.

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

ZIFT (zygote intrafallopian transfer). An ART procedure where 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 before it begins to divide) into the woman's fallopian tube through a small incision in her abdomen.

Please contact us with any questions or suggestions at ARTinfo@cdc.gov.