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Routine Prenatal Care

Terminology

• Estimated date of confinement (EDC)
• Last menstrual period (LMP)
  
• Miscarriage/abortion (Ab)
• Gravida (G) = pregnancy
• Parity (P) = deliveries  
• Advanced Maternal Age (AMA) = >35 years old

Shorthand

A patient’s simplified OB history can be written using the common abbreviations

Gravida (number of pregnancies) = G

Parity (number of births) = P

Abortions (#of aborted pregnancies) – Ab

Example:

A woman’s OB history includes three pregnancies with a miscarriage between her two living children.  How would that be represented in shorthand?   G3P2Ab1

Due date

Due date = estimated date of confinement (EDC)

• Nägele’s rule:  
  • EDC = 1st day of LMP + 1 year + 7 days – 3 months
    
• Other versions:
  • EDC = 1st day of LMP + 280 days
  • EDC = 1st day of LMP + 9 months and 7 days

Physical exam signs of pregnancy

Chadwick’s sign – bluish coloring of cervix, vagina and labia due to venous congestion secondary to an increase in estrogen.  Typically seen 6- 8 weeks after conception.

Hegar’s sign – a softening of the uterine isthmus allowing palpation or compression of the connection between the fundus and the cervix.  Typically seen from 4-12 weeks after conception.

Routine office visits

Things to check at exam visits – baby movement, fundal height, fetal heart rate, U/S and possibly a vaginal examination.  

A Review of Prenatal Testing

U/S – (Performed throughout pregnancy)

• Fetal viability
• Detect presence of more than one fetus
• Placental localization
• Checking amniotic fluid levels
• Position of the fetus
• Gestational age/due date
• Weights and size of fetus
• Detect fetal malformations
  • Cardiac abnormalities
  • Cleft palate
  • Hydrocephalus
  • Spina bifida
  • etc.
• Biophysical profile – 3rd trimester, 30 minutes 
  • Breathing –    1 or more normal breathing episode
  • Movement –   2 or more movements
  • Muscle Tone   1 episode of extension/flexion
  • Heart Rate –   2 or more accelerations of at least 15 bpm in a 20 minute period.
  • Amniotic Fluid levels – 1 or more adequate pockets of fluid

Chorionic Villus Sampling (Typically performed at 10-12 weeks)

CVS is a biopsy of placental tissue used to obtain chromosomal information about the fetus.

Indications Include:

• Family history of genetic disorder
• Abnormal ultrasound
• Advanced maternal age alone may be an indication

Diagnostic for:

• Inherited disorders including sickle cell, cystic fibrosis and Tay-Sachs disease
• Chromosomal abnormalities such as Down Syndrome and trisomy 18

Risks of CVS:

• Small  risk of infection
• Miscarriage risk is approximately 0.7%-1.3% which is about 3.5 times the rate for  an amniocentesis

Quadruple Screen (Performed between 15-18 weeks)

This is a maternal blood test checking levels of  AFP ( alpha-fetoprotein), hCG (human chorionic gonadotropin , Estriol and Inhibin – A.  The levels of these hormones in the mother’s blood are used to provide probabilities of genetic disorders in the fetus.

Indications:

• Offered to all women

Diagnostic for:

• The Quadruple screen is only a screening test and is not used for definitive diagnosis .  It is used to stratify risk of genetic disorders such as Down Syndrome and other trisomies.

Risk of Quadruple screen:

• Simple blood draw

Amniocentesis (Typically performed at 15-18 weeks)

Amniocentesis is a technique using a needle to withdraw amniotic fluid from the uterine cavity.   

Indications:

• Advanced maternal age alone is an indication
• Family history of genetic disorder

• Abnormal ultrasound
• Abnormal quad screen
• Testing fetal lung development at 32 weeks

Diagnostic for:

• Inherited disorders including sickle cell, cystic fibrosis and Tay-Sachs disease
• Chromosomal abnormalities such as Down Syndrome and trisomy 18

Risks of amniocentesis:

• Amniotic fluid leaking which is typically self limited.
• Almost no risk of direct fetal injury
• Indirect fetal risk – some slight increase in orthopedic problems and lung development in babies born following amniocentesis vs a control group
• Risk of miscarriage is approximately 0.2%-0.3%

Oral Glucose Challenge (Performed between 24-28 weeks)

Indications:

• All pregnant women should be tested for gestational diabetes.

Diagnostic for:

• Gestational diabetes

Risks:

• Simple blood draw

Screening:  50 grams of glucose are administered orally.  

• Normal at 1 hour glucose is below 140

Diagnostic: Pt is fasting and then given a 100 grams of glucose orally

• Fasting normal is below 100
• At 1 hour less than 180
• At 2 hours less than 155
• At three hours less than 140

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