1. Pregnancy and Prenatal Care

Question 1

What hormone do OTC urine pregnancy tests test for?

What produces this hormone and what are its levels throughout pregnancy?

Answer 1

beta subunit of hCG

b-hCG is produced by the placenta and will rise to a peak of 100,000 mIU/mL by 10 weeks of gestation, decrease throughout 2nd trimester, and then level off at approx 20,000 to 30,000 mIU/mL in the third trimester

Question 2

Terms:

• From time of fertilization until pregnancy is 8 weeks along
• After 8 weeks until time of birth
• Period between delivery and 1 year of age

Answer 2

Terms:

• From time of fertilization until pregnancy is 8 weeks along: embryo
• After 8 weeks until time of birth: fetus
• Period between delivery and 1 year of age: infant

Question 3

Terms:

• First trimester:
• Second trimester:
• Third trimester:

Answer 3

Terms:

• First trimester: lasts until 12 weeks but is also defined as up to 14 weeks’ GA
• Second trimester: 12-14 until 24-28 wks’ GA
• Third trimester: 24-28 - delivery

Question 4

Terms:

• Infant delivered prior to 24 weeks:
• Infant delivered between 24-37 weeks:
• Infant delivered between 37-42 weeks:
• A pregnancy carried beyond 42 weeks:

Answer 4

Terms:

• Infant delivered prior to 24 weeks: previable
• Infant delivered between 24-37 weeks: pre-term
• Infant delivered between 37-42 weeks: term
• A pregnancy carried beyond 42 weeks: postterm

Question 5

Gravidity & Parity notation

Answer 5

Gravidity (G) = # times woman has been pregnant

Parity (P) = # of pregnancies that led to birth at or beyond 20 weeks’ GA or of an infant weighing more than 500 g

P = TPAL (term deliveries, pre-term deliveries, abortuses, # of living children)

Question 6

Dating of Pregnancy:

What is the GA of a fetus?

What is the DA of a fetus?

Answer 6

GA: Age in weeks and days measured from the LMP

DA: # of weeks and days since fertilization

**Because fertilization usually occurs about 14 days after the first day of the prior menstrual period, the GA is usually 2 weeks more than the DA**

Question 7

How to determine estimated date of delivery

Answer 7

Subtract 3 months from the LMP and add 7 days

Thus, a pregnancy with an LMP of January 16, 2012 would have an EDC of October 23, 2012.

Exact dating uses an EDC calculated as 280 days after a certain LMP.

Question 8

Signs and Symptoms of Pregnancy

Answer 8

Signs:

• Bluish discoloration of vagina and cervix (Chadwick sign)
• Softening and cyanosis of the cervix at or after 4 week (Goodell sign)
• Softening of the uterus after 6 week (Ladin sign)
• Breast swelling and tenderness
• Development of the linea nigra from umbilicus to pubis
• Telangiectasias
• Palmar erythema

Symptoms:

• Amenorrhea
• Nausea and vomiting
• Breast pain
• Quickening–fetal movement

Question 9

Physiology of Pregnancy: CV

SVR decreases during pregnancy, resulting in a fall in arterial blood pressure. This decrease is most likely due to ______?

Answer 9

Elevated progesterone, leading to smooth muscle relaxation

Question 10

Physiology of Pregnancy: Respiratory

What is the big change you see?

How does this change affect oxygen delivery to the fetus and CO2 removal from the fetus?

Answer 10

30-40% increase in tidal volume despite the fact that TLC is decreased by 5% due to elevation of diaphragm

This increase in Vt decreases the expiratory reserve volume by about 20%. The increase in Vt with a constant respiratory rate leads to an increase in minute ventilation of 30% to 40% which in turn leads to an increase in alveolar (PAO2) and arterial (PaO2) PO2 levels and a decrease in PACO2 and PaCO2 levels.

PaCO2 decreases to approx 30 mm Hg by 20 weeks’ GA. –> increased CO2 gradient b/w mother and fetus –> facilitates O2 delivery to fetus and CO2 removal from fetus

Question 11

Physiology of Pregnancy: Endocrine

The hormone hCG is composed of two dissimilar alpha and beta subunits. What is the alpha subunit identical to?

What changes in hCG levels do you see?

What produces hCG and what does it do?

Answer 11

What is the alpha subunit identical to? alpha subunits of LH, FSH, and TSH

Levels of hCG double approx every 48 hrs during early pregnancy, reaching a peak at approx 10-12 weeks, and thereafter declining to reach a steady state after week 15

The placenta produces hCG, which acts to maintain the corpus luteum in early pregnancy. The CL produces progesterone, which maintains the endometrium. Eventually, the placenta takes over progesterone production and the CL degrades into the corpus albicans. Progesterone levels inc. over the course of pregnancy –> causes relaxation of smooth muscle, which has multiple effects on GI, CV, and GU systems.

Question 12

Physiology of Pregnancy: Endocrine

What are the two major changes in thyroid hormones during pregnancy?

Answer 12

1. Estrogen stimulates TBG –> elevation in total T3 and T4, but free T3 and T4 remain relatively constant
2. hCG has a weak stimulating effect on the thyroid, likely because its alpha subgroup is similar to TSH –> slight increase in T3 and T4 and slight decrease in TSH early in pregnancy

Overall, however, pregnancy = euthyroid state

Question 13

Nutritional req:

avg woman requires 2,000-2,500 kcal/day… what is the caloric req increased to during pregnancy and while breastfeeding?

Answer 13

inc by 300 kcal/day during pregnancy and by 500 kcal/day when breastfeeding… therefore, pregnancy is the caloric equivalent of eating for 1.15

Question 14

Weight gain during pregnancy: numbers

Answer 14

Most pts gain between 20-30 lbs.

If overweight, gain 15-25 lbs. If underweight, gain 28-40 lbs.

Question 15

Maternal weight is followed serially throughout the pregnancy as a proxy for adequate nutrition… what can large weight gains toward the end of pregnancy be a sign of?

Answer 15

Fluid retention and preeclampsia

Question 16

Routine Tests in Prenatal Care:

2nd and 3rd trimester

Answer 16

2nd:

• MSAFP/triple or quad screen
• Obstetric U/S
• Amniocentesis for women interested in prenatal dx

3rd:

• Hematocrit
• RPR/VDRL
• GLT
• GBS culture

Question 17

When is screening for maternal serum alpha fetoprotein (MSAFP) usually performed? Correlation?

Answer 17

B/w 15-18 weeks

Elevation is correlated with inc. risk of neural tube defects, and a decrease is seen in some aneuploidies (i.e. Down Syndrome)

Question 18

2nd trimester visit:

Triple screen =

Quad screen =

Answer 18

Triple screen = MSAFP, b-hCG, estriol

Quad screen = “ “ + inhibin A

Question 19

3rd trimester visit:

What type of contractions might you see?

Answer 19

Braxton Hicks contractions… if these become regular, the cervix is examined to r/o pre-term labor

Question 20

What is the GLT?

What is the GTT?

Answer 20

Glucose Loading Test =

Screening test for gestational diabetes at 27-29 weeks (3rd trimester visit) = 50 g oral glucose loading dose and check serum glucose 1 hour later… if this value is greater than or equal to 140 mg/dL, a GTT is administered

Glucose Tolerance Test =

Diagnostic test for gestational diabetes = fasting serum glucose measurement and then administration of 100 g oral glucose loading dose… serum glucose is then measured at 1, 2, and 3 hours after oral dose is given

This test is indicative of GD if there is an elevation in 2 or more of the following threshold values:

fasting glucose, 95 mg/dL;

1 hr, 180 mg/dL;

2 hr, 155 mg/dL; or

3 hr, 140 mg/dL

Question 21

Routine Problems of Pregnancy (11):

Answer 21

• Back pain
• Constipation
  
  • decreased bowel motility 2/2 elevated progesterone
• Contractions
  
  • Occasional irregular contractions that do not lead to cervical change = Braxton Hicks contractions.. will occur several times per day up to several times per hour
  • Dehydration may cause increased contractions
• Dehydration
  
  • B/c of expanded intravascular space and increased third spacing of fluid, pts have difficult time maintaining their intravascular volume status
• Edema
  
  • Compression of IVC and pelvic veins
• GERD
  
  • Relaxation of LES and increase transit time in stomach –> reflux + nausea
• Hemorrhoids
  
  • Increased venous stasis and IVC compression –> congestion in venous system
• PICA
  
  • Rarely, a pt will have cravings for inedible items such as dirt/clay
• Urinary Frequency
• Varicose veins
• Round Ligament Pain
  
  • During 2nd trimester or early in 3rd trimester, pain is likely 2/2 rapid expansion of the uterus and stretching of ligamentous attachments
    *

Question 22

In the third trimester, U/S can be used to monitor high-risk pregnancies by obtaining biophysical profiles (BPP), fetal growth and fetal Doppler studies.

What does the BPP look at?

Answer 22

Five categories and gives a score of either 0 or 2 for each:

1. Amniotic fluid volume
2. Fetal tone
3. Fetal activity
4. Fetal breathing movements
5. Nonstress test (NST), which is a test of the FHR

BPP of 8 to 10 or better is reassuring.

Question 23

Fetal Lung Maturity:

How to assess?

Answer 23

Amniotic fluid sample obtained through amniocentesis is analyzed

Classically, the lecithin to sphingomyelin (L/S) ratio has been used as a predictor… Lecithin inc. as lungs mature. Sphingomyelin decreases beyond about 32 weeks.

Question 24

How much folic acid to take to reduce risk of neural tube defect?

Answer 24

400 micrograms folic acid supplements the month before conception and during 1st trimester

Question 25

Hyperemesis gravidarum

Answer 25

Severe form of morning sickness in which women lose more than 5% of their prepregnancy weight and go into ketosis With severe vomiting, a metabolic alkalosis would be expected

Question 26

On fetal monitoring, late FHR decelerations are concerning for?

Answer 26

Uteroplacental insufficiency