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Plasma volume expansion in early pregnancy
I M Bernstein1, W Ziegler, G J Badger
1Department of Obstetrics and Gynecology, University of Vermont College of Medicine, Burlington, Vermont, USA. ibernste@zoo.uvm.edu
Obstetrics and Gynecology
|May 8, 2001
Summary
Plasma volume expansion in early pregnancy is not detectable until after six weeks. By 12 weeks, a significant 14% increase is observed, indicating crucial early pregnancy changes.
Area of Science:
- Physiology
- Reproductive Medicine
- Maternal-Fetal Medicine
Background:
- Plasma volume changes are critical in early pregnancy.
- Understanding the timing of these changes is essential for monitoring pregnancy progression.
Purpose of the Study:
- To determine the time course of plasma volume expansion in early human pregnancy.
Main Methods:
- Prospective measurement of plasma volume using Evans blue dye dilution.
- Measurements taken across menstrual cycle phases and at specific gestational time points (LH surge + 16, +28, +70 days).
- Analysis of data from 21 subjects over 38 cycles, with 10 conceiving viable pregnancies.
Main Results:
- Plasma volume showed significant changes across the observation period in pregnant subjects (P <.008).
- No significant plasma volume expansion was detected at 16 or 28 days post-LH surge compared to menstrual cycle phases.
- By 70 days post-LH surge (12 menstrual weeks), plasma volume was significantly elevated compared to baseline and early pregnancy estimates.
Conclusions:
- Plasma volume expansion in early pregnancy is not identifiable until after the sixth menstrual week.
- By 12 menstrual weeks, plasma volume expands by approximately 14% over follicular phase measurements.