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Maternal physiologic adaptations to early human pregnancy
J F Clapp1, B L Seaward, R H Sleamaker
1Department of Obstetrics and Gynecology, University of Vermont College of Medicine, Burlington 05405.
American Journal of Obstetrics and Gynecology
|December 1, 1988
Summary
Maternal physiological changes begin early in pregnancy, before they are functionally needed. These early adaptations in body composition, cardiopulmonary, and metabolic systems suggest preparative roles and potential diagnostic value.
Area of Science:
- Physiology
- Pregnancy Research
- Maternal Adaptations
Background:
- Pregnancy involves significant physiological changes.
- The timing and necessity of these adaptations, particularly early in gestation, are not fully understood.
Purpose of the Study:
- To test the hypothesis that maternal physiological adaptations occur early in pregnancy, preceding functional necessity.
- To investigate changes in body composition, cardiopulmonary, and metabolic functions during the embryonic period.
Main Methods:
- Serial measurements in 20 women before pregnancy and at 7 and 15 postconceptional weeks.
- Assessment of body composition, plasma volume, heart rate, mean arterial pressure, minute ventilation, oxygen consumption, respiratory exchange ratio, blood glucose, and blood lactate.
Main Results:
- Significant increases in body fat (2%) and plasma volume (11%) by week 7, accounting for weight gain.
- Cardiopulmonary changes included increased heart rate (16%), decreased mean arterial pressure (9%), elevated minute ventilation (24%), and increased oxygen consumption (10%).
- Metabolic changes showed an increased respiratory exchange ratio and decreased lactate levels (15%), with unchanged resting glucose.
Conclusions:
- Maternal physiological adaptations begin early in pregnancy, supporting the hypothesis of preparative changes.
- These early adaptations may hold diagnostic significance for monitoring pregnancy progression.