Abnormalities of Pregnancy 1

Question 1

List the common causes for iatrogenic preterm birth.

Answer 1

• Placenta previa
• Vasa previa
• Placental abruption
• Fetal growth restriction
• Preeclampsia
• Rh alloimmunization (previously called isoimmunization)

Question 2

How common is placenta previa, and what is its definition?

Answer 2

• Accounts for 20% of third-trimester bleeding
• Definition: Implantation of placenta in location where it covers cervical os characterized by painless bright red vaginal bleeding

Question 3

What are some common risk factors that can lead to placenta previa?

Answer 3

• Prior cesarean delivery
• Multiparity
• Advanced maternal age
• Prior placenta previa
• Smoking

Question 4

What are the goals for diagnosis in placenta previa? What are some possible complications?

Answer 4

• Goals of diagnosis
  
  • Awareness: pelvic rest
  • Planned cesarean section at 37 weeks gestation
  • Expectant management and administration of antenatal corticosteroids if appropriate
• Possible complications
  
  • Placenta accreta

Question 5

What is the definition of vasa previa? What are some possible mechanisms?

Answer 5

• Defintion: Vaginal bleeding that is arising from fetal vessels (fetal blood)
• Possible contributing mechanisms: Remains unknown

Question 6

What are the goals of diagnosis in vasa previa?

Answer 6

• Technically, can do an Apt test (alkaline solution to blood à fetal blood cells are resistant to lysis, blood should remain red)
• Practically, no time to do Apt test and need to deliver rapidly (only takes minutes for fetus to bleed out its entire blood volume)

Question 7

What is the definition of placental abruption? What are some possible contributing mechanisms?

Answer 7

• Definition: Premature separation of the placenta from the uterine wall and most typically characterized by vaginal bleeding in the presence of uterine contractions
  
  • Vaginal bleeding may not always be evident (concealed bleeding behind the placenta)
• Possible contributing mechanisms
  
  • Remains unknown

Question 8

What are some risk factors that can lead to placental abruption?

Answer 8

• Hypertension
• Prior placental abruption
• Abdominal trauma
• Smoking
• Cocaine
• Uterine anomalies or submucosal fibroids
• PPROM

Question 9

What is the management of placental abruption?

Answer 9

• Administration of antenatal corticosteroids if appropriate
• Delivery based upon maternal and fetal status

Question 10

What is the definition of fetal growth restriction?

Answer 10

Fetus who is less than 10th percentile for a given gestational age

Question 11

What are some common causes of fetal growth restriction?

Answer 11

• Fetal
  
  • Aneuploidy
  • Fetal anomalies
  • Infection (TORCH)
  • Multiple gestation
• Uteroplacental
  
  • Uteroplacental insufficiency as a result of processes such as:
    
    • chronic hypertension
    • preeclampsia
    • chronic abruption
• Maternal
  
  • Malnutrition
  • Illicit drug use
  • Smoking
  • Maternal medical conditions:
    
    • cyanotic heart disease
    • anemia
    • chronic pulmonary disease
    • poorly controlled hyperthyroidism

Question 12

What is involved in the diagnosis of fetal growth restriction and what are the goals?

Answer 12

• Diagnosis
  
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• Goals of diagnosis
  
  • Counseling parents about prognosis and if applicable, options regarding pregnancy management
  • Institution of appropriate antenatal surveillance
  • Administration of antenatal corticosteroids if appropriate

Question 13

What is the definition of preeclampsia? What are some possible contributing mechanisms?

Answer 13

• Typically only severe preeclampsia requires preterm delivery
• Definition: New-onset hypertension and proteinuria
  
  • Edema no longer technically part of definition as it is common in routine pregnancies
  • Severe preeclampsia
    
    • BP > 160/110 on two occasions 6 hours apart
    • 24-hr urine protein > 5 g
    • Maternal symptoms: Headache, visual changes, epigastric/RUQ pain
    • Hepatic injury/failure
    • Renal dysfunction/failure
    • Pulmonary edema
    • Coagulopathy
    • HELLP syndrome (hemolysis, elevated liver enzymes, low platelets)
• Possible contributing mechanisms
  
  • Poor trophoblast remodeling of maternal spiral arterioles
  • Possible increased production of sFlt-1 along with other anti-angiogenesis proteins

Question 14

What is the management of preeclampsia?

Answer 14

• Definitive therapy → delivery regardless of gestational age
• Expectant management if mild (and preterm) or if severe disease that is stable
• MgSO4 during intrapartum course and first 24 hours post-partum

Question 15

What is the definition of Rh alloimmunization?

Answer 15

• Definition: Exposure of Rh negative mother to Rh positive fetal blood where she has produced antibodies against D antigen
  
  • Antibodies result in hemolytic disease of fetus/newborn in subsequent pregnancy
  • Alloimmunization can also occur with other maternal IgG antibodies against RBC antigens (e.g. Kell, Duffy, Kidd)

Question 16

What are the steps in prevention of Rh alloimmunization?

Answer 16

• Administration of Rh immune globulin to all pregnant women who are Rh negative (unless certain that father is Rh negative)
  
  • Routine
    
    • 28 weeks gestation
    • 40 weeks or after delivery
  • Also with any other concern for breakage in fetomaternal barrier
    
    • First trimester bleeding/miscarriage
    • Ectopic pregnancy
    • Abdominal trauma with concern for abruption
    • Abruption
    • Previa
    • Amniocentesis/CVS
• One 300 ug dose covers 30 cc whole fetal blood (or 15 cc fetal RBCs)

Question 17

What are the management strategies for Rh alloimunization?

Answer 17

• Paternal genotype
• Fetal antigen status
• Serial antibody titers
• Fetal middle cerebral artery doppler peak-systolic velocity indices
• Periumbilical cord blood sampling with intrauterine transfusion