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Magnetic Resonance Imaging (MRI) -- A procedure using a magnet linked to a computer to create pictures of areas inside the body.

Maturation Arrest -- A testicular condition in which at one stage of sperm production all sperm development halts throughout all testicular tubules. May result in oligospermia or azozoospermia.

Measles-Mumps-Rubella Vaccine (MMR) -- A vaccine recommended for women who have a low antibody titre to Rubella since Rubella (German Measles) can be very damaging to a fetus.

Meiosis -- The cell division, peculiar to reproductive cells, which allows genetic material to divide in half. Each new cell will contain twenty-three chromosomes. The spermatids (immature sperm) and ova (eggs) each contain twenty-three chromo-somes, so when they combine (fertilize), the baby will have a normal complement of forty-six.

Menarche -- The time when a woman first menstruates.

Menopause -- The time a woman stops menstruating.

Menorrhagia -- Heavy or prolonged menstrual flow.

MESA -- See Microsurgical Epididymal Sperm Aspiration.

Methotrexate -- A toxic anticancer drug that is an analogue of folic acid and an antimetabolite. Used as an antineoplastic agent (to attack abnormal tissue growth). Sometimes used to treat ectopic and molar pregnancies.

Metrodin (Pure FSH) -- An injectable form of Follicle Stimulating Hormone used to stimulate ovulation.

Metrorrhagia -- Menstrual spotting during the middle of the cycle.

Micro Injection Fallopian Transfer (MIFT) -- A technique similar to GIFT and FASIAR that may be used in lieu of in vitro fertilization for women with patent (clear and open) tubes. After egg retrieval the eggs are mixed with sperm and then immediately injected through into the woman's fallopian tubes for in vivo fertilization. Rather than using laparoscopy, this method uses need aspiration of follicles and injection into the follopian tubes.

Microsurgical Epididymal Sperm Aspiration (MESA) -- Using microsurgery to remove sperm from the epididymis for use in in vitro fertilization, often with ICSI.

Miscarriage (MC, m/c) -- Spontaneous loss of an embryo or fetus from the womb. See Abortion.

Missed Abortion/Missed Miscarriage -- The fetus dies in the uterus but there is no bleeding or cramping. A D&C will be needed to remove the fetal remains and prevent complications. See Abortion.

Mitosis -- The division of a cell into two identical cells in which all forty-six human chromosomes are duplicated; the first division of the germ cell.

Mittleschmerz -- The discomfort felt on one or both sides of the lower abdomen at the time of ovulation.

MMR -- See Measles-Mumps-Rubella Vaccine.

Molar Pregnancy (Trophoblastic Disease) -- the fertilization of an egg without a nucleus. A baby (usually anomalous) may or may not be present, and the placenta develops into a nonmalignant tumor called a hydatidiform mole. The layer of cells that line the gestational sac and normally give rise to the chorionic villi convert into a mass of clear, tapioca-like vesicles instead of into a healthy placenta. The fertilized egg then deteriorates. Probably caused by a chromosomal abnormality in the fertilized egg. A continuous or intermittent brownish discharge is the prime symptom. Treated by a D&C and sometimes methotrexate.

Morphology -- The shape of sperm as studied in a semen analysis.

Mosaicism -- Having more than one blood line. For example, instead of having all 46XX cells, a mosaic may have a combination of 46XX and 45X cells. See Klinefelter's and Turner's Syndrome.

Motility -- The measurement of motion and forward progression of sperm in a semen analysis.

MRI -- See Magnetic Resonance Imaging.

Mucus -- Secretions from a gland that can be water, gel-like, stretchy, sticky or dry. Fertile mucus resembles raw egg whites (watery and stretchy).

Mutagen -- Substance that alters the genetic structure of the sperm or egg before conception.

Mycoplasma -- An infectious agent that falls structurally between a virus and a bacterium. Thought to be related to pregnancy loss and perhaps infertility as well. See Ureaplasma.

Myomectomy -- Surgical removal of a uterine fibroid.