1. Pregnancy and Prenatal Care Flashcards
What hormone do OTC urine pregnancy tests test for?
What produces this hormone and what are its levels throughout pregnancy?
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
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
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
Terms:
- First trimester:
- Second trimester:
- Third trimester:
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
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:
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
Gravidity & Parity notation
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)
Dating of Pregnancy:
What is the GA of a fetus?
What is the DA of a fetus?
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**
How to determine estimated date of delivery
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.
Signs and Symptoms of Pregnancy
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
Physiology of Pregnancy: CV
SVR decreases during pregnancy, resulting in a fall in arterial blood pressure. This decrease is most likely due to ______?
Elevated progesterone, leading to smooth muscle relaxation
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?
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
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?
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.
Physiology of Pregnancy: Endocrine
What are the two major changes in thyroid hormones during pregnancy?
- Estrogen stimulates TBG –> elevation in total T3 and T4, but free T3 and T4 remain relatively constant
- 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
Nutritional req:
avg woman requires 2,000-2,500 kcal/day… what is the caloric req increased to during pregnancy and while breastfeeding?
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
Weight gain during pregnancy: numbers
Most pts gain between 20-30 lbs.
If overweight, gain 15-25 lbs. If underweight, gain 28-40 lbs.
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?
Fluid retention and preeclampsia
