Salt, aldosterone and extrarenal Na+ - sensitive responses in pregnancy

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Abstract

Outside of pregnancy excessive salt consumption is known to be harmful being linked to increased blood pressure and cardiovascular disease. However, pregnancy represents a major change to a woman's physiology resulting in an intimate adaptation to environmental conditions. It is now becoming apparent that salt is essential for a number of these changes during pregnancy including haematological, cardiac adaptations as well as directly influencing placental development and the uteroplacental immune environment. The present review discusses the important role that salt has during normal pregnancy and evidence will also be presented to show how the placenta may act as a salt sensing organ temporarily, yet substantially regulating maternal blood pressure.

Highlights

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The placenta may function as an extrarenal regulator of maternal blood pressure.
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Na ⁺handling in pregnancy is completely different to the non-pregnant situation.
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Na ⁺may actually lower blood pressure in pregnancy affected with pre-eclampsia.
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Aldosterone is an important regulator of placental and fetal development.
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Na ⁺ may compensate for aldosterone deficiency in pregnancy.

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Most cited references 59

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The systemic hemodynamic profile of human pregnancy is characterized by a decrease in mean arterial pressure, a rise in cardiac output and plasma volume in association with an increase in renal plasma flow and glomerular filtration rate. The factors and the time course responsible for the initial hemodynamic changes seen in human pregnancy have not been completely documented. We hypothesize that systemic and renal hemodynamic changes occur early, prior to the presence of the fetal-placental unit. Thirteen women were studied prior to and immediately following conception in identical fashion at gestational weeks 6, 8, 10, 12, 24 and 36. Individuals underwent mean arterial pressure, cardiac output, inulin and PAH clearance determinations. Mean arterial pressure decreased by six weeks gestation (mid follicular 81.5 +/- 2.6 vs. six weeks 68.7 +/- 2.0 mm tig, P < 0.001) in association with a significant increase in cardiac output, a decrease in systemic vascular resistance and an increase in plasma volume. Renal plasma flow and glomerular filtration rate increased by six weeks gestation. Plasma renin activity and aldosterone concentration increased significantly by six weeks, whereas norepinephrine levels did not change throughout pregnancy. Atrial natriuretic peptide levels increased later, at 12 weeks gestation. Plasma cGMP levels decreased and cGMP clearance increased by six and eight weeks, respectively. Peripheral vasodilation occurs early in pregnancy prior to full placentation in association with renal vasodilation and activation of the renin-angiotensin-aldosterone system. Plasma volume expansion occurs early, followed later by increases in ANP concentration, suggesting that ANP increases in response to changes in intravasular volume.

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Author and article information

Contributors

Paula Juliet Scaife

Markus Georg Mohaupt

Journal

Journal ID (nlm-ta): Placenta

Journal ID (iso-abbrev): Placenta

Title: Placenta

Publisher: Elsevier

ISSN (Print): 0143-4004

ISSN (Electronic): 1532-3102

Publication date PMC-release: 1 August 2017

Publication date (Print): August 2017

Volume: 56

Pages: 53-58

Affiliations

[a ]Division of Child Health, Obstetrics and Gynaecology, School of Medicine, 1st Floor Maternity Unit, City Hospital Nottingham, Nottingham NG5 1PB, United Kingdom

[b ]Department of Clinical Research, University of Bern, Switzerland, 3Sonnenhof Hospital, Berne, Switzerland

Author notes

[∗ ]Corresponding author. Paula.Scaife@ 123456nottingham.ac.uk

Article

Publisher ID: S0143-4004(17)30101-7

DOI: 10.1016/j.placenta.2017.01.100

PMC ID: 5526786

PubMed ID: 28094006

SO-VID: 93726e5b-4cbf-416f-a13e-26e6f5ff54a3

License:

This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

History

Date received : 23 September 2016

Date revision received : 30 December 2016

Date accepted : 9 January 2017

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