Fertility, Infertility & Reproductive Medicine Glossary 

Aneuploidy - Derived from the Greek for "not the correct number," this term refers to any chromosomal imbalance or variation from the normal complement of 46 chromosomes, denoted 46xy for boys and 46xx for girls. Having an extra chromosome is called trisomy. Trisomy 21 is also known as Down syndrome. Lacking a chromosome is called monosomy. Most monosomic embryos fail to implant. Partial aneuploidies are also possible with variable clinical presentations. Aneuploidy is the cause of approximately 80% of miscarriages, as most forms of aneuploidy are not compatible with life.
 
Blastocyst – the stage of development reached by embryos after 5 to 6 days. Blastocyst, or blasts, have approximately 200 cells and a fluid-filled central cavity. At the blastocyst stage, cells have differentiated into the inner cell mass (ICM) and trophectoderm (TE). The ICM eventually will develop into the baby while the TE forms the membranes and placenta.
 
Cervix – The cervix is the lower end of the uterus, located at the top of the vagina, and is a passageway between the vagina and uterus.
 
Comprehensive Chromosome Screening (CCS) - A form of PGS that counts every chromosome in the embryo (normally 22 pairs of autosomes and 2 sex chromosomes for a total of 46xx or 46xy). Technologies used to perform CCS include microarray, PCR, comparative genomic hybridization (CGH) and array CGH. Aneuploidy of every chromosome has been found when testing embryos with CCS.
 
Cumulus oophorus - Specialized follicular cells that adhere to the egg (oocyte) and are involved in egg maturation and fertilization.
 
Egg – see Oocyte.
 
Embryo – The fertilized egg after cell division begins until the start of the third month of pregnancy.
 
Epididymis – A convoluted tubule adjacent to each testis; carries sperm to the vas deferens.
 
Estrogen – The female sex hormone produced by the follicles, responsible for many functions including the development of the lining of the uterus.
 
Fallopian Tubes – Two thin tubes that extend from each side of the uterus toward the ovaries. They are a passageway for eggs and sperm and site of fertilization.
 
Fertilization – The union of sperm and egg.
 
Follicle – A small fluid-filled sac in the ovary containing the egg.
 
Follicle Stimulating Hormone (FSH) – Hormone secreted by the pituitary gland in the brain that stimulates the maturation of ovarian follicles in females and sperm cell maturation in males.
 
Fluorescence In Situ Hybridization (FISH) - A genetic technique that involves developing probes that label specific regions in the genome with fluorescent tags. While quite accurate when testing samples withlarge numbers of cells such as blood lymphocytes and fetal cells from amniocentesis, FISH was never validated for use with single cells from embryo biopsies. Several large clinical trials have conclusively proven that FISH-based PGS does not improve pregnancy rates or prevent miscarriage. FISH-based PGS is not a form of CCS because only a handful of chromosomes can be labelled.
 
Intracytoplasmic Sperm Injection (ICSI) - A technique developed in the early 1990s in which fertilization is achieved by injecting an individual sperm into an individual egg. ICSI is recommended for couples with very low sperm counts, but it is also necessary for PGD and CCS as DNA from excess sperm could decrease the accuracy of genetic tests.
 
Luteinizing Hormone (LH) – Hormone secreted by the pituitary gland in the brain that stimulates the release and maturation of eggs in females and testosterone production in males.
 
Microarray - A gene chip in which hundreds of thousands of tiny fragments of DNA are attached to a small plate. A patient's or embryo's DNA can be divided into similar size fragments to determine the relativequantity of specific regions called single nucleotide polymorphism (SNPs).
 
Oocyte – The female sex cell, or egg, produced in the ovaries and released from a follicle during ovulation; also called ovum.
 
Ovaries – Female reproductive glands in which the ova, or eggs, are formed. The ovaries are located in the pelvis, one on each side of the uterus.
 
Ovulation – The release of the egg from the ovary.
 
Preimplantation Genetic Diagnosis (PGD) - A technique in clinical use for over 20 years that involves biopsying individual cells from an embryo, amplifying the genetic material and then using PCR to detect individual genes. This can be used to screen embryos for a variety of inherited disorders when the parents are known carriers. Disorders successfully prevented with PGD at RMANJ have included cystic fibrosis, sickle cell disease, fragile X syndrome, and chromosomal translocations.
 
Preimplantation Genetic Screening (PGS) - A variation of PGD in which a biopsy is performed to screen for aneuploidy (chromosomal imbalance) in the embryo. PGS has typically been offered to women of advanced age who are at increased risk for aneuploidy, but approximately 30% of embryos are aneuploid even in women under age 35. Theoretical advantages of PGS would include increased pregnancy rates per transfer and decreased miscarriage rates.
 
Polymerase Chain Reaction (PCR) - A technique developed by Nobel Prize winner Kary Mullis that revolutionized the field of molecular genetics. Using specific primers, PCR can result in millions of copies of a segment of DNA within minutes.
 
Progesterone – A hormone secreted by the ovary after ovulation has occurred. It prepares the lining of the uterus for implantation of a fertilized egg.
 
Prostate – A gland in the male reproductive system just below the bladder. It secretes seminal fluid, a milky substance that combines with sperm (produced in the testicles) to form semen.
 
Semen – The fluid that is released through the penis during ejaculation. Semen is made up of sperm from the testicles and fluid from the prostate and other glands.
 
Sperm – The male reproductive cell, formed in the testicle. A sperm unites with an egg to form an embryo.
 
Testes – Also called testicles. Pair of male sex glands that produce sperm and male hormone testosterone.
 
Testosterone – A hormone produced by the testes, responsible for the development of male secondary sex characteristics and functioning of the male reproductive organs.
 
Uterus – The pear-shaped organ in women that holds and nourishes the growing embryo and fetus. Commonly called the womb.
 
Vas Deferens – Tube through which sperm travel from the epididymis as they mature.
 
Vitrification - A technique for ultra-rapid freezing of eggs or embryos that minimizes the risk of ice-crystal formation. Embryos that are vitrified at the blastocyst stage have more than a 95% chance of surviving when warmed, significantly higher than with traditional "slow freezing." The efficacy of egg vitrification is currently being studied an an ongoing clinical trial at RMANJ.
 
Zygote – The fertilized egg before cell division begins.