Reproduction II: Pregnancy Flashcards
It takes ____ days for the embryo to travel through the tube to the uterus, then it takes about ____ days to implant into the uterus.
It takes three days for the embryo to travel through the tube to the uterus, then it takes about 3 more days to implant into the uterus.
The earliest hCG is detectable in circulation about ___ days after conception.
The earliest hCG is detectable on a serum pregnancy test is about ___ days after conception.
The earliest hCG is detectable on a urine pregnancy test is about ___ days after conception.
The earliest hCG is detectable in circulation about eight days after conception.
The earliest hCG is detectable on a serum pregnancy test is about fourteen days after conception.
The earliest hCG is detectable on a urine pregnancy test is about twenty eight days after conception.
Blastocyst structure
Pre-implantation development of a fertilized egg
The trophoblast becomes. . .
. . . the placenta and membranes.
By convention, obstetricians date pregnancies from. . .
. . . the first day of the last menstrual period (LMP) rather than from conception, with day one of the cycle assigned to the first day of the menses.
Naegele’s Rule for estimating due date
EDD (in the following year) = LMP - 3 months + 7 days
hCG bears substantial structural resemblance to ___, which causes receptor cross-reactivity.
hCG bears substantial structural resemblance to LH and TSH, which causes receptor cross-reactivity.
Pregnancy tests employ an antibody that is specific to. . .
. . . just the beta subunit of hCG
This ensures that they do not cross-react with the alpha subunit in FSH, LH, or TSH.
How a home pregnancy test works
The first prenatal visit for a pregnancy should occur at . . .
. . . 8 weeks gestation (ideally before 12 weeks)
All women planning to become pregnant receive a ___ supplement.
All women planning to become pregnant receive a 0.4 mg daily folate supplement.
This reduces the risk of neural tube defects in early pregnancy,
Laboratory studies collected at first prenatal visit
- Blood and Rh typing,
- antibody screening,
- hepatitis and rubella titers,
- HIV and syphilis screening,
- HbsAg,
- HCV,
- chlamydia and gonorrhea screening
When does the placenta take over as a producer of progesterone?
At ~10 weeks (end of the first trimester)
Endocrine changes during pregnancy
- Increased T3/T4 and TBG (net neutral)
- Increased insulin secretion
- Increased cortisol binding globulin levels (via estrogen), net neutral
Nausea and vomiting in pregnancy are principally due to . . .
. . . progesterone and hCG elevations.
These symptoms resolve by 14 weeks for most women.
Gastric reflux and constipation in pregnancy
- Common
- Gastrointestinal motility and gastric emptying are reduced due to increased levels of progesterone
- This is magnified by mass effect of uterus in 2nd and 3rd trimesters
- Prolonged GI transit time results in more water resorption, leading to constipation
- Gastric reflux is caused by progesterone-mediated decrease of lower esophageal sphincter tone.
- Iron given to pergnant women to ensure adequate red cell mass also causes constipation
Fetal iron
If iron is not readily available, the fetus uses iron from maternal stores
Thus, the production of fetal hemoglobin is usually adequate even if the mother is iron deficient
Gall stones in pregnancy
Gallbladder motility is also slowed by progesterone, resulting in increased biliary cholesterol saturation and increased risk of gallstones.
Circulating volume in pregnancy
- Progresses throughout pregnancy, increasing by 45-50% and peaking at 32 weeks (third trimester).
- Needed for the additional blood flow to the uterus, metabolic needs of fetus, and increased perfusion of other organs, especially kidneys
Cardiac output in pregnancy
During pregnancy, cardiac output rises gradually and reaches its peak around 20-24 weeks
Primarily due to increased stroke volume and, to a lesser extent, increases in heart rate
How does intravascular volume increase during pregnancy?
- Progesterone acts as a vasodilator
- Blood pressure declines and the RAAS is activated
- Sodium and water retention
Heart rate increases ~___ during pregnancy
Heart rate increases ~15-20 beats per minute during pregnancy
Summary of cardiovascular changes in pregnancy
- Maternal total body water ↑ 6-8 liters
- Fetus, placenta, amniotic fluid ↑ 3.5 liters
- Total blood volume ↑ 50%
- Red cell mass ↑ 35%
- Blood pressure ↓ 6-10 mm Hg
- Heart Rate ↑ 12-18 beats/min
- Stroke volume ↑ 10-30%
- Cardiac Output ↑ 33-45%
Supine hypotensive syndrome
Third trimester, pregnant patients are prone to experiencing postural hypotension when lying supine, where the enlarged uterus can compress the IVC thus reducing preload, resulting in presyncopal symptoms.
This problem can be alleviated by putting the patient in left lateral decubitus position to displace the uterus from compressing the IVC.
Dyspnea during early pregnancy is thought to be. . .
. . . a central (“controller”) effect caused by progesterone (which is a respiratory stimulant)
Chest wall changes of pregnancy
- Relaxation of the ligaments between the ribs and sternum, due to the softening effect from the hormone relaxin (produced by the placenta)
- Subcostal angle increases from 70 to 100 degrees
- Chest circumference expands by 5-7 cm
Pulmonary changes in pregnancy (PFT values)
- Total lung capacity increases by 5%
- Tidal volume increases by 40%
- Minute ventilation increases by 40%
- Respiratory rate unchanged