Glossary of Terms

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M

Meiosis

The cellular division that occurs in sexual gonads (ovaries and testicles) to reduce the number of chromosomes in the egg and the sperm by half (from 46 down to 23 chromosomes). After fertilization, when the egg and sperm unite, the normal complement of 46 chromosomes is re-established in the new embryo. Errors in the process of meiosis occur frequently in human eggs and may be one of the major causes of implantation failure and miscarriage in humans.

Menopause

The period in a woman's life when menstruation stops. The average age of menopause in the United States is 51. The few years prior to menopause, also called the climacteric or peri-menopause, menstrual cycles become irregular in many women. 

MESA

Microsurgical Epididymal Sperm Aspiration (MESA) is a surgical procedure to remove sperm from the epididymis in men who have an obstruction of the vas deferens or epididymis (or congenital absence of the vas deferens). This procedure is also used for obtaining sperm from men who have had a prior vasectomy. Unlike the TESE procedure, millions of sperm can usually be obtained and excess sperm are frozen for subsequent IVF cycles if needed. The sperm are then injected into the female partner's eggs (see ICSI).

Metformin

An oral medication used to treat insulin-resistance associated with Polycystic Ovarian Syndrome.

Micromanipulation

Advanced techniques used to manipulate gametes, i.e. eggs and sperm, to enhance successful fertilization and implantation. Intracytoplasmic sperm injection is one form of micromanipulation. (See ICSI). Embryo biopsy for pre-implantation genetic diagnosis and assisted hatching are other micromanipulation techniques.

Mitosis

The replication of cells by equal division. Soon after fertilization, the zygote undergoes successive mitoses and thus yields an embryo. All organs in the body that regenerate do so by mitosis.

Morula

An early phase of a growing embryo that resembles a mulberry. This stage is the typical stage for a Day 4 embryo.