Medical Glossary: M

Malnutrition

Term used to describe any nutrition based disorder. Unbalanced, insufficient or excessive diet are all causes as are the body's ability to absorb or process nutrition.

Mammogram

A term used to describe the photograph made from an x-ray of the breast's soft tissues.

Mask of Pregnancy

The discoloration or pigmentation of the forehead, cheeks and nose associated with pregnancy or the use of oral contraceptives. The pigmentation may be permanent or disappear after pregnancy or use of oral contraceptives. It is also called the chloasma or melasma.

McDonald Cerclage

A term used to describe a surgical procedure performed on an incompetent cervix. A suture in the form of a drawstring is used to hold the cervical opening closed during pregnancy.

Meconium

Waste material that collects in the intestinal tract of the unborn fetus. It is thick and sticky in consistency and varys in color from dark green to black.

It is formed from a variety of substances from amniotic fluid to secretions in the intestinal tracts. The presence of meconium in the amniotic fluid is usually a sign of fetal distress.

After birth the color and consistency of the stool changes with the ingestion of breast milk or formula.

Melanoma

Pigmentation of the skin composed of melanocytes. They develop over a long period, usually several months or even years and most commonly in people with fair skin with light eyes.

Melanomas may or may not be cancerous and are usually excised for biopsy.

Melasma

The discoloration or pigmentation of the forehead, cheeks and nose associated with pregnancy or the use of oral contraceptives. The pigmentation may be permanent or disappear after pregnancy or use of oral contraceptives. It is also called the chloasma or the mask of pregnancy.

Membranes

Either of two sets of protective sacs, called the amnion and chorion, which surround the baby while it is in the uterus during pregnancy.

Meningomyelocele

A congenital birth defect of the central nervous system in which the spinal column and membranes protrude through an opening of the vertebral column.

Menstrual Age

The age of the fetus as determined from the first day of the last menstrual period (280 days till birth) rather than the date of conception, which is two weeks shorter (266 days till birth). Also called the gestational age.

Menstruation

Term used to describe the cycle that results in a discharge of bloody fluid from the uterus. See the Pregnancy Diary Week Two for a complete description of the menstrual cycle.

Mesoderm

The mesoderm, also known as the mesodermal germ layer is an area of tissue which will layer form into other muscular structures. Later in the pregnancy, the mesoderm will form to become the internal organs, including kidneys and ureters, and other muscular tissues.

Metaplasia

A medical term used to describe a structural change in tissue to a type that is not normal for that tissue.

Microcephaly

Term used to describe a congenital birth defect that results in the baby having an unusually small head and some degree of mental retardation.

A microcephalic head is more than two standard deviations below average circumference for age, sex, race and gestational age.

Causes include an autosomal recessive disorder, chromosomal abnormality, or some toxic stimulus. Other causes include maternal infection or trauma, especially during the third trimester.

Microphthalmia

A congenital birth defect that results in the baby being born with one or two unusually small eyes. If no other eye defects are present it is called pure micropthalmia.

Milk Ejection Reflex

Also known as the let-down reflex, it is normal in a lactating woman, stimulated by touch of the nipple, which results in the release of milk from the glands in the breast.

Milk Glands

Glands in the female breast that begin produce milk during the last stages of pregnancy and postnatally.

Milk Letdown

A term used to describe the tingling or cramping sensations felt in a woman's breast when milk flows into the breast ducts.

Minimum Brain Dysfunction

More commonly known as attention deficit disorder (ADD) or attention deficit hyperactivity disorder (ADHD), it is a syndrome that affects primarily children and adolescents and is characterized by learning disabilities. The symptoms are associated with functional deviations of the central nervous system, while lacking signs of major neurologic or psychiatric disturbance.

Symptoms include inpaired perception, conceptual, language, memory and motor skills. Hyperactivity and decreased attention span are common.

The condition is ten times more common in boys and result from genetic factors, biochemical imbalances or perinatal injury or disease. While there is no cure, syptoms eventually subside and treatment includes medication and a modified diet.

Miscarriage

Medically called spontaneous abortion, more than 10% of all pregnancies end before the twentieth week. Causes are almost entirely due to a blighted ovum that is incompatible with life.

Missed Miscarriage

A condition in which the pregnancy terminates without bleeding or cramping. It is usually detected weeks or months later by ultrasound. Infections and a reduced ability for the mother's blood to clot may result.

Mittelschmerz

An abdominal pain felt in the region of the ovaries during the release of an egg. It is felt in many women and is considered useful in identifying the fertile period of the menstrual cycle. It is popularly called stomach cramps.

Molar Pregnancy

An abnormal pregnancy with a cystic growth of the placenta. A hydatidiform mole develops from the trophoblastic tissue of the early embryonic stage of development.

In a molar pregnancy, all of the usual signs are highly exaggerated. The growth of the uterus is unusually rapid, morning sickness is often severe and there are high levels of chorionic gonadotropin as well as high blood pressure. In such cases the uterus must be evacuated to prevent the mole from developing into choriocarcinoma. Also known as gestational trophoblastic disease or GTN.

Molding

A natural process through which the baby's head is shaped as it passes through the birth canal during labor and delivery.

The baby's head will often become elongated, with the bones of the skull overlapping at the suture lines. Any changes to the shape of the head will resolve themselves naturally during the first few days of life after birth.

Mongolism

Better known as Down's Syndrome, mongolism is a congenital abnormality in which the baby is born mentally retarded, with an average IQ of 50 - 60 and with physical deformation of the face (low set ears, sloping forehead, mongoloid eyes), and shortness of stature.

Down's syndrome is caused by an extra chromosome 21 present in the G group. In a small percentage of cases it can be caused by the switching of chromosomes 14 or 15 in the D group or chromosome 21 or 22.

Down's syndrome occurs in about 1 in 650 births, and is more commonly associated with children of mother's over the age of 35. Incidence in children of mothers over the age of 40 can be as high as 1 in 80.

Down's syndrome can be detected prenatally through amniocentesis. The mortality rate is high within the first few years. It is also known as trisomy 21 or trisomy G syndrome.

Monilia

Monilia is a common microscopic fungal organism normally present in the mucus membranes of the mouth, intestines and vagina. Under certain circumstances it may become superficially infected, and rarely seriously infected. Also known as thrush or Candida albicans.

Monilial Vulvovaginitis

Commonly called a yeast infection, and medically termed candidiasis, it is any infection caused by the bacteria Candida, usually Candida Albicans. Common manifestations are diaper rash, intertrigo, vaginitis and thrush. Oral and topical medication can be used for treatment.

Monitoring

An electromechanical device that provides a visual, audible or graphical signal that is used to monitor a specific function. In pregnancy it usually refers to an electronic fetal monitor.

Monozygotic Twins

A pregnancy in which two children are produced from the same ovum, which has split during early embryonic development.

Monozygotic twins are always of the same sex, share the same genetic makeup and blood groups.

Both children resemble each other physically, mentally and psychologically.

Monozygotic twins are also called enzygotic twins, true twins, identical twins or uniovular twins.

Montgomery's Tubercles

The small bumps on the areola surrounding the nipple, they are sebaceous glands which normally enlarge during pregnancy.

Morning Sickness

A non-technical term used to describe nausea and vomiting of pregnancy and in severe cases called Hyperemesis Gravidarum. It is most common between the sixth and fourteeth weeks as a result of the hormonal changes taking place in the body.

To minimize discomfort eat small meals that are easy to digest, taking care not to allow the stomach to be empty.

Morphine

Short for morphine sulfate. An opiate analgesic used to numb severe pain. See the Pregnancy Guide Drugs & Pregnancy: Opiates for more information about opiates and their effects on the body, pregnancy and the unborn fetus.

Morula

An early stage of embryonic development where a solid spherical mass of cells have formed from the fertilized ovum. It is an intermediate stage between the zygote and the blastocyst.

Mucus

The viscous secretions of the mucus membranes and glands. Mucus contains mucin, white blood cells, water, salts and exfoliated cells.

Mucus Plug

Cervical secretion of mucus used to seal the uterus throughout pregnancy. It is usually released just prior to labor.

Multigravida

A medical term for a woman who is in her second or subsequent pregnancy. The term for a first time pregnancy is primagravida.

Multiple Pregnancy

A term used to describe the development of two or more babies in the uterus at the same time.

Mutation

A change in the genetic structure, usually spontaneous, that changes the expression of the gene and is transmitted to future generations.

Myelin

A white fatty substance that forms sheaths around the nerve fibers through the body.

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