Long-term acid-base measurements in the fetal and maternal baboon

Area of Science:

• Primatology
• Maternal-Fetal Medicine
• Physiology

Background:

• Understanding maternal-fetal acid-base balance is crucial for perinatal care.
• The baboon serves as a relevant animal model for studying human pregnancy physiology.

Purpose of the Study:

• To investigate the relationship between maternal and fetal acid-base parameters in baboons.
• To establish baseline acid-base values in pregnant baboons during the third trimester.

Main Methods:

• Eight baboons were studied in a tether system during the third trimester of pregnancy.
• Analysis of variance was used to analyze acid-base indexes.
• Maternal and fetal blood samples were collected to measure pH, PO2, PCO2, base deficit, and oxygen saturation.

Main Results:

• Fetal carotid artery pH was 7.40, PO2 27.5 mm Hg, PCO2 34.0 mm Hg, and base deficit 3.0 mEq/L.
• Maternal values were pH 7.48, PO2 100.7 mm Hg, PCO2 26.4 mm Hg, and base deficit 3.6 mEq/L.
• During active labor, the fetus exhibited a decrease in pH and PO2, indicating mild acidosis and hypoxemia.

Conclusions:

• The baboon fetus demonstrates slightly higher pH and lower PCO2 compared to human fetuses.
• Maternal-fetal gradients for PO2, base deficit, and oxygen saturation across the placenta are comparable between baboons and humans.