Third Trimester Notes

Question 1

What is asymmetrical intrauterine growth restriction?

Answer 1

It is the most common type of growth abnormality demonstrating normal cranial growth and a decrease in abdominal growth.

Question 2

What is a biophysical profile?

Answer 2

An objective means for assessing fetal well-being.

Question 3

What defines hypertension in pregnancy?

Answer 3

Systolic pressure ≥140 mm Hg or diastolic pressure ≥90 mm Hg.

Question 4

What is oligohydramnios?

Answer 4

Amniotic fluid below the normal range for gestational age, with a total volume <200 mL.

Question 5

What is polyhydramnios?

Answer 5

Amniotic fluid above the normal range for gestational age, with a total volume >2000 mL.

Question 6

What is postterm pregnancy?

Answer 6

Gestation greater than 42 weeks.

Question 7

What is macrosomia?

Answer 7

A condition where accelerated fetal growth results in an infant with a birth weight greater than 4000 g in nondiabetic mothers or greater than 4500 g in diabetic mothers; associated with birth asphyxia and trauma.

Question 8

What is symmetrical intrauterine growth restriction?

Answer 8

A fetal growth abnormality resulting in a proportionally small fetus.

Question 9

What is vernix caseosa?

Answer 9

Fatty material found on the fetal skin and in amniotic fluid late in pregnancy.

Question 10

What measurements are taken in the third trimester? 7

Answer 10

1. Biparietal diameter (BPD)
2. Head circumference (HC)
3. Abdominal circumference (AC),
4. Femur length (FL)
5. Amniotic fluid volume
6. Head circumference-to-abdominal circumference ratio (HC/AC)
7. Etimated fetal weight.

Question 11

What is the significance of the head circumference-to-abdominal circumference ratio (HC/AC)?

Answer 11

During the early third trimester, the head circumference is slightly larger than the abdominal circumference; by late third trimester, it is typically equal to or slightly larger.

Question 12

What is the preparation for transabdominal imaging?

Answer 12

Requires bladder distention; adults should drink 28 to 32 oz of water 1 hour before examination.

Question 13

What are the contraindications for endovaginal imaging?

Answer 13

Any patient who does not or cannot willingly consent to the examination; if the pain becomes too severe, terminate examination.

Question 14

What is the recommended transducer selection for adults?

Answer 14

Use 3.5 to 5.0 MHz for transabdominal, 4.0 to 8.0 MHz for endovaginal, and 3.5 to 5.0 MHz for translabial imaging.

Question 15

What is the patient positioning for transabdominal imaging?

Answer 15

Supine position.

Question 16

What is the examination protocol for ultrasound? 6

Answer 16

1. Begin with a quick survey of the entire gravid uterus
2. Assess fetal age and growth using biometric measurements
3. Evaluate fetal presentation and viability
4. Amniotic fluid volume
5. Placenta location and grade
6. Length of internal cervical os.

Question 17

What are the indications for third trimester ultrasound? 7

Answer 17

1. Fetal growth
2. Amniotic fluid volume
3. Fetal well-being
4. Fetal presentation
5. Late prenatal care
6. Placenta location
7. Follow-up on previous ultrasound findings.

Question 18

What does intrauterine growth restriction (IUGR) result from? What is it defined as?

Answer 18

1. Insufficient oxygen and nutrition delivery to the fetus from the placenta
2. Defined as a fetal weight at or below the 10th percentile for gestational age.

Question 19

What are the clinical findings of asymmetric intrauterine growth restriction? 3

Answer 19

1. Decrease in abdominal circumference, normal head circumference and femur length
2. Decrease in amniotic fluid volume
3. Increase in HC/AC ratio.

Question 20

What is the definition of macrosomia?

Answer 20

Fetal weight above 4000 g in nondiabetic mothers or >4500 g in diabetic mothers or above the 90th percentile for gestational age.

Question 21

What are the functions of amniotic fluid? 5

Answer 21

1. Maintains intrauterine temperature
2. Allows fetal movement
3. Protects the developing fetus
4. Prevents adherence of the amnion to the fetus
5. Promotes lung growth and development.

Question 22

When does the volume of amniotic fluid stop increasing?

Answer 22

Increases progressively until about 33 gestational weeks.

Question 23

What is the method for assessing amniotic fluid volume using the Amniotic Fluid Index (AFI)?

Answer 23

Dividing the uterus into four equal parts and measuring the deepest unobstructed pocket in each quadrant.

Question 24

What are the abnormal findings for oligohydramnios?

Answer 24

AFI below 5 cm, below the 5th percentile for gestational age, and largest single pocket below 1 cm.

Question 25

What does the biophysical profile assess? 5

Answer 25

Fetal well-being through five parameters: 1. Fetal tone 2. Fetal movement 3. Fetal breathing movement 4. Amniotic fluid volume 5. Nonstress test.

Question 26

What is fetal presentation?

Answer 26

The relationship of the fetal head with the long axis of the uterus.

Question 27

What are the types of breech presentation?

Answer 27

Frank breech, complete breech, and footling breech.