Antenatal Care: Confirming and dating pregnancy, Establishing gestation, routine labsal age with ultrasound,

Question 1

Identify the tests used to confirm pregnancy and establish gestational age

Answer 1

• LMP (based on the woman having regular cycles)
• Urine hCG test
• Serum hCG test
• Ultrasound ( transabdominal and transvaginal)

Question 2

Explain how to calculate the estimated due date using Naegele’s rule

Answer 2

(LMP -3m)+7days

Question 3

Compare the serum pregnancy test to the urine pregnancy test

Answer 3

• Urine preg test:
• measures hCG in urine
• Qualitative - only tells us whether the woman is pregnant or not.
• Doesn’t help establish Gestational age
• Serum preg test
• measures hCG in the blood
• Quantitative - tells us the amount of hCG present in the blood.
• Can be used along with US to establish gestational age - tells us whether we should be able to see anything on the US.

E.g. If serum hCG is at least 2000 - can see something in the uterus using transvaginal US.
If serum hCG is over 6000, we can see something using transabdominal US.

Question 4

Recognize the most accurate method to establish gestational age

Answer 4

Ultrasound

• It’s often more accurate than measuring from your last menstrual period, because dating from the last menstrual period assumes that every woman has 28-day menstrual cycles, and many do not.

Question 5

Recognize the most accurate method to establish the gestational age

Answer 5

Ultrasound

• It’s often more accurate than measuring from your last menstrual period, because dating from the last menstrual period assumes that every woman has 28-day menstrual cycles, and many do not.

Question 6

Identify the ultrasound parameter used to determine gestational age in the first trimester

Answer 6

• Parameter used - Crown-rump length
• Accuracy within 1 week of LMP
• US is only going to tell us how far along the
  pregnancy is based on the date of conception.
• US can be off by one week in the 1st trimester
• LMP is the most accurate if consistent with the transvaginal us.
• If LMP is unknown, then US is the most accurate.
• If within a week of each other, then take the LMP.

Question 7

Recognize the disadvantage of using the last menstrual period to determine gestational age

Answer 7

• assumes that the woman has regular periods and that her cycles are 28 days long.

Question 8

Identify the ultrasound parameters used to assess gestational age in the second and third trimesters

Answer 8

• Biparietal diameter (between parietal bones in the head)
• Abdominal circumference
• Femur length

Question 9

Describe the accuracy of ultrasound in calculating gestational age in the first, second, and third trimesters

Answer 9

ist trimester - US can be off by 1 week
2nd trimester - off by 2 weeks
3rd trimester - off by 3 weeks

2nd and 3rd trimesters can be influenced by fetal, maternal, and placental factors.

1st trimester us only influenced by the date of conception.

Question 10

List the factors that influence the accuracy of ultrasound in measuring gestational age

Answer 10

2nd and 3rd trimesters can be influenced by fetal, maternal, and placental factors.

1st trimester us only influenced by the date of conception.

Question 11

Recognize the B-HCG level at which the gestational sac is visible on the transvaginal ultrasound

Answer 11

at least 2000

Question 12

List the routine screening tests conducted in the initial prenatal visit

Answer 12

• Blood type and Rh factor
• Complete blood count (check Hb and Hct - pregnant women have physiological anemia so good to see starting point)
• Infections - Rubella, HIV, Syphilis
• Pap smear for Gonorrhea and chlamydia
• Hemoglobinopathies and inherited diseases

Question 13

Identify the infections that all women should be screened for in the initial prenatal visit

Answer 13

• HIV
• Rubella
• Gonorrhea and Chlamydia
• Syphilis
• Hepatitis B (and C)

Question 14

Recall the screening guidelines for a pap smear

Answer 14

A Pap Smear, usually done during your first prenatal visit is a test used to look for changes in the cells of the cervix which indicate cervical cancer or conditions that may develop into cancer.

• Cultures for baseline labs
• Gonorrhea and chlamydia

Question 15

Name the prenatal screening tests for genetic and hemoglobin disorders

Answer 15

African-American women - sickle cell trait
Ashkenazi Jews - Canavan’s disease
caucasian women - CF

Question 16

List the routine screening tests conducted throughout pregnancy

Answer 16

• Anatomy Ultrasound (18-23 weeks)
• Gestational Diabetes (24-28 weeks)
• Anti-D if Rh is negative (give Rhogam so antibodies don’t form complications in later pregnancies)
• Pertussis vaccination (3rd trimester against whooping cough)
• Screening for group B strep (36-38 weeks so cultures remain valid)

Question 17

Recall the screening guidelines for Down syndrome and gestational diabetes

Answer 17

Advanced maternal age
- but also for all women
- Anatomy US done at 18-23 weeks gestation
- check for all structures - brain, heart, intestines

Question 18

Describe the management of Rh-negative women

Answer 18

Give Rhogam at 28 weeks
- bind antigens so the maternal body doesn’t form antibodies against the next fetus.

Question 19

Recall the screening guidelines for group B streptococcus and recognize the potential complications if left untreated

Answer 19

• 36-38 weeks
• so the cultures remain valid
• normal flora of the vagina but can cause infant pneumonia and meningitis.