••• Chapter 3^ Physiology of Normal Pregnancy^33
❍ All vitamins are found in human breast milk except which one?
Vitamin K. This is why vitamin K is administered to newborns.
Formula is also deficient in vitamin K.
❍ The increase and decrease of which factors cause the increased risk of deep vein thrombosis in
pregnancy?
Patients who are pregnant are known to have an increase in clotting factors VII, VIII, X, and XII as well as
an increase in prothrombin and fibrinogen. Also, they are found to have a decrease in the anticoagulant
protein S.
❍ What is the normal fibrinogen level in pregnancy?
A normal fibrinogen (factor I) during pregnancy can reach a level of 600 mg/dL at term. This increases from a
prepregnancy value of 300 mg/dL.
❍ How does pregnancy affect cardiac output?
Cardiac output increases to its maximum in the first trimester and this increase continues to term. The increase is
1.5 L/min above the nonpregnancy average.
❍ Blood flow to most organ systems increases during pregnancy. Which vital organ system does not receive
more flow during pregnancy?
Cerebral blood flow remains unchanged.
❍ How does pregnancy affect arterial blood pressure?
There is relatively little change in systolic blood pressure (SBP). Diastolic blood pressure (DBP) decreases from
12 to 26 weeks and increases to reach the nonpregnancy value at 36 weeks. This causes an increase in pulse
pressure during the second trimester.
❍ What is the definition of mean arterial blood pressure (MAP)?
MAP 5 SBP^1 2(DBP)
3❍ How does pregnancy affect systemic vascular resistance (SVR)?
Both SVR and pulmonary vascular resistance are decreased. Remember: MAP = SVR × CO. MAP does not change
that much in pregnancy; however, CO is very much increased. SVR must decrease by definition. By midpregnancy,
the SVR is about 1000 dynes/sec/cm^5 compared with the nonpregnancy value of 1500 dynes/sec/cm^5. Be aware that
SVR may increase if the patient is in the supine position due to aortic compression.
❍ Does pulmonary capillary wedge pressure (PCWP) change in late pregnancy?
No. PCWP and central venous pressure (CVP) are not changed significantly in late pregnancy when compared
with 12 weeks postpartum. Normal averages are 6 mmHg and 4 mmHg, respectively.
❍ What is the normal glomerular filtration rate (GFR) in pregnancy?
125 cc/min. The average prepregnancy rate is 90 cc/min.