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Magnesium sulfate (Epsom salts)

A naturally occurring mineral used to prevent and treat seizures in preeclampsia - eclampsia.

Mask of pregnancy (melasma)

See chloasma

Massively parallel genomic sequencing

Technologies capable of determining the order of the nucleotide bases (adenine, guanine, cytosine, and thymine) in an enormous number of DNA molecules  at the same time.


Inflammation of the breast, usually caused by infection in a woman who is breast-feeding or has recently delivered. Signs of mastitis include painful, tender, red, swollen breasts, and fever. Breast engorgement, cracked or damaged skin around the nipple, and blocked milk ducts appear to predispose the new mother to mastitis. The condition is treated with antibiotics, and  the mother may continue to breast feed while being treated.

Maternal mortality ratio

The number of maternal deaths directly or indirectly related to pregnancy per 100,000 live births in a given time period.

According to the ICD 9 " A maternal death is defined as the death of a woman while pregnant or within 42 days of the termination of pregnancy, irrespective of the duration and the site of the pregnancy, from any cause related to or aggravated by the pregnancy or its management but not from accidental or incidental causes."

Maternal deaths are further subdivided into two groups

  • Direct obstetric deaths: those resulting from obstetric complications of the pregnant state (pregnancy, labor and puerperium); from interventions, omissions or incorrect treatment; or from a chain of events resulting from any of the above.
  • Indirect obstetric deaths: those resulting from previous existing disease or disease that developed during pregnancy and that were not due to direct obstetric causes but were aggravated by the physiologic effects of pregnancy.

Some include both liveborn and stillborn infants in the denominator for less-developed areas.

MAP (Mean Arterial Pressure)

The average blood pressure in a person's arteries during one cardiac cycle. MAP = (CO × SVR) + CVP OR MAP ~ [(2 x diastolic blood pressure) + systolic blood pressure] / 3.

CO= cardiac output, SVR =systemic vascular resistance, CVP=  central venous pressure

Mean corpuscular volume (MCV)

The average red blood cell size expressed in femtoliters (fl). One femtoliter (fL) = 10-15L = 1 cubic micrometer (μm3).

Mean corpuscular hemoglobin (MCH)

The average amount of hemoglobin inside a red blood cell (RBC) expressed in picograms (pg).

Mean corpuscular hemoglobin concentration (MCHC)

The average concentration of hemoglobin in the red blood cells expressed as a percent.


The thick, mucoid,  dark green contents of the fetal intestine which is the first rectal discharge from the newborn. Meconium is composed of the bile secretions of the liver, intestinal glands, amniotic fluid, lipids, blood group substances and fetal skin cells.


An abnormally small head (a head circumference of 3 standard deviations below the mean for the gestational age) usually associated with abnormal neurological findings and mental retardation. Microcephaly be caused by a chromosomal abnormality, a gene defect, an infection such as rubella, cytomegalovirus, or toxoplasmosis, exposure to drugs such as alcohol, aminopterin ,or hydantoin, or a maternal condition such as phenylketonuria (PKU).

Microcephaly occurring with no neurologic defect (other than mental deficiency) and no other malformation is called primary microcephaly and may be inheritable.


An abnormally small jaw (mandible).

Micrognathia  may occur as an isolated finding or may be found in association with many syndromes including trisomy 18, Treacher-Collins syndrome, Pierre Robin syndrome, Russell-Silver syndrome , Seckel syndrome, Progeria, and Smith-Lemli-Opitz syndrome


Shortening of all the long bones (humerus, radius, ulna, femur, tibia, and fibula) of the extremities.

Micromelia is a characteristic of many forms of skeletal dysplasias including, thanatophoric dysplasia, homozygous achondroplasia, osteogenesis imperfecta Type II and III, achondrogenesis, diastrophic dysplasia, short rib polydactyly syndrome,  Chondroectodermal dysplasia, Campomelic dysplasia, Kniest dysplasia, dyssegmental dysplasia, hypophosphatasia (perinatal lethal).


A person who provides pregnancy, birth and postnatal support for normal births. There are three types of midwives practicing in the United States:

  • Certified Nurse-Midwife (CNM)
    Certified nurse midwives are registered nurses who are also trained in midwifery. They receive certification from the American College of Nurse Midwives.
  • Certified Professional Midwife (CPM)
    A certified professional midwife is trained in midwifery and has met the standards for certification set by the North American Registry of Midwives.
  • Lay Midwife
    An uncertified or unlicensed midwife who was educated through informal routes  rather than through a formal program.

Milia (milk spots)

Tiny, 1 to 2 mm, white bumps (nodules) found on the face and nose of newborn infants. They also may be found on the mouth or roof of the mouth. Milia in the newborn are epidermoid cysts believed to occur in sebaceous glands that are not fully developed. The bumps usually  disappear within a few weeks of delivery without treatment.

Miscarriage (spontaneous abortion, SAB)

A pregnancy loss before 20 weeks' gestation calculated from the date of onset of the last menses. Spontaneous abortion occurring before 12 weeks' is called early abortion. Abortion occurring between 12 to 20 weeks' is called late abortion. Up to 20 % of all recognized pregnancies end in miscarriage with 80% occurring during the first trimester.

Symptoms of miscarriage include bleeding with or without cramping.

The risk of miscarriage recurring in a woman with no live births after one miscarriage appears to be approximately 13 %, after two prior miscarriages 25%, and after three miscarriages  50%. However, if she has had a least one live birth the risk having another miscarriage after 3 prior miscarriages is 30%.


1. Stenchever MA, Droegemueller W, eds. Comprehensive Gynecology. 4th ed. St. Louis: Mosby, 2001p. 413-415
2. American College of Obstetricians and Gynecologists. ACOG Education Pamphlet AP090 -- Early Pregnancy Loss: Miscarriage and Molar Pregnancy 2002
Available at:
Retrieved 3/6/2009

Molding (moulding)

Abnormal shape of a baby’s head caused by pressure on the head during childbirth

Mongolian spot

A bluish-gray birthmark over the lower back and rump of infants that may be mistaken for bruising. Mongolian spots are most commonly seen in infants of African, Asian, Hispanic, and Native American descent. The spots are believed to be caused by entrapment of the cells that produce skin pigment (melanocytes) in the the innermost layer of skin (dermis). They are harmless and most will have completely faded by the age five.


One amniotic sac (bag of water)


One placenta

Monozygotic twins (identical twins):

Two separate embryos conceived from a single fertilized egg. Identical twins account for about 30% of naturally occurring  twins in the United States

Montevideo units (MVUs)

A measure of uterine contractile force defined as the sum of the uterine contraction pressures above the resting tone for all contractions in a 10 minute interval, or the average uterine contraction pressure above the resting tone for all contractions in a 10 minute interval multiplied by the number on contraction in ten minutes.

4 contractions are each measured to have a pressure of ~ 50 mm Hg above the baseline in a ten minute period .  50 + 50 +50 +50 =  200 Montevideo units (MVUs)


50 mm Hg X 4 contractions= 200 Montevideo units (MVUs)

Caldeyro-Barcia R, et al. A quantitative study of the action of synthetic oxytocin on the pregnant human uterus. J Pharmacol Exp Ther 1957; 121:18.J Pharmacol Exp Ther. 1957 Sep;121(1):18-31. No abstract available.
PMID: 13481824

Mucus plug (cervical mucus plug)

An accumulation of thick clear secretions in the cervical canal.


A woman who has been pregnant more than once regardless of whether she carried the pregnancy to term.


A woman who has given birth to a viable infant at least once before. A multiple gestation counts as a single birth.

Myelomeningocele (meningomyelocele , spina bifida cystica)

A birth defect in which the spinal cord and the membranes covering the spinal cord (meninges) protrude through a cleft in the bones of the spine (veretebrae) usually in the lower back or tailbone (lumbosacral) region. Myelomeningocele is a form of spina bifida that typically results in paralysis and loss of sensation below the level of the spinal defect.



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