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Cited by 372Pregnancy and preeclampsia studiesIron Metabolism and DisordersPregnancy-related medical research

Blood Volume Changes in Normal Pregnancy

Hytten, Frank·1985·Clinics in Haematology
DOI 10.1016/s0308-2261(21)00496-3
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Abstract

The plasma volume and total red cell mass are controlled by different mechanisms and pregnancy provides the most dramatic example of the way in which that can happen. A healthy woman bearing a normal sized fetus, with an average birth weight of about 3.3 kg, will increase her plasma volume by an average of about 1250 ml, a little under 50% of the average non-pregnant volume for white European women of about 2600 ml. There is little increase during the first trimester, followed by a progressive rise to a maximum at about 34-36 weeks, after which little or no further increase occurs. It seems certain that the frequently observed fall in plasma volume in the last six weeks of pregnancy is an artefact of measurement due to poor mixing of tracer when the woman lies supine and obstructs the circulation to her lower limbs. The maximum increase depends largely on the size of the conceptus. It is somewhat increased, perhaps to a mean of 1300 ml, in association with the bigger baby of multiparae and increases still more with twins, triplets and quadruplets. Red cell mass increases by relatively much less, a rise of about 250 ml (some 18% of the non-pregnant volume) in women who take no supplemental iron, and between 400 and 450 ml when iron supplements are taken. The rise is probably linear from the end of the first trimester to term, and there is some evidence of a preliminary fall in red cell mass during the first trimester. As a result of the relatively much greater increase in plas…

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  • The trajectories observed in this large cohort aligned with macro-physiological adaptations well-documented in classic obstetric literature, such as those pioneered by Hytten and Lukaski, which track progressive hemodilution and maternal-fetal tissue expansion.

    “The trajectories observed in this large cohort aligned with the macro-physiological adaptations that are well-documented in classic obstetric literature, such as those pioneered by Hytten [1] and Lukaski [21], which track progressive hemodilution and maternal-fetal tissue expansion.”

    From Trimester-Specific Bioelectrical Impedance Reference Curves in Physiological Pregnancy: Mapping Maternal Body Composition and Hydration Trajectories (2026) · cites this paper as [1]

  • The remarkable stability of the TBW trajectory across different pre-pregnancy BMI strata suggests that gestational fluid expansion is a highly preserved, 'hardwired' evolutionary adaptation designed to support placental perfusion.

    “The remarkable stability of the TBW trajectory across different pre-pregnancy BMI strata suggested that gestational fluid expansion is a highly preserved, 'hardwired' evolutionary adaptation designed to support placental perfusion [1-3].”

    From Trimester-Specific Bioelectrical Impedance Reference Curves in Physiological Pregnancy: Mapping Maternal Body Composition and Hydration Trajectories (2026) · cites this paper as [1]

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Authors
Hytten, F.
Corresponding author
Hytten, Frank
Venue
Clinics in Haematology
Publisher
Elsevier BV
Published
1985-10
Volume
14
Issue
3
Pages
601-612
ISSN
0308-2261 (ISSN-L)
DOI
10.1016/s0308-2261(21)00496-3
OpenAlex
W117546959
Cited by
372
References
30
Citations by year
2026: 10 · 2025: 16 · 2024: 7 · 2023: 18 · 2022: 12 · 2021: 13 · 2020: 21 · 2019: 19 · 2018: 15 · 2017: 21 · 2016: 10 · 2015: 12 · 2014: 22 · 2013: 12 · 2012: 17
FWCI
6.91
Type
journal article
Language
en
Open access
closed
Licence
Locations
  • Clinics in Haematology (publishedVersion)
  • PubMed (publishedVersion)
Topics
  • Health Sciences › Medicine › Obstetrics and Gynecology › Pregnancy and preeclampsia studies
  • Health Sciences › Medicine › Hematology › Iron Metabolism and Disorders
  • Health Sciences › Medicine › Public Health, Environmental and Occupational Health › Pregnancy-related medical research
Keywords
pregnancy, plasma expansion, red cell mass, hematocrit, blood volume changes, iron supplementation, multiparity, multiple pregnancy, fetal size, hemodilution
MeSH terms
Adolescent, Adult, Birth Weight, Blood Volume, Blood Volume Determination, Erythrocyte Volume, Female, Hematocrit, Humans, Infant, Newborn, Iron, Plasma Volume, Pregnancy, Pregnancy, Multiple, Time Factors

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