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Poor spontaneous and oxytocin-stimulated contractility in human myometrium from postdates pregnancies

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Arrowsmith, Sarah, Quenby, Siobhan, Weeks, Andrew, Burdyga, Theodor and Wray, Susan. (2012) Poor spontaneous and oxytocin-stimulated contractility in human myometrium from postdates pregnancies. PLoS One, Vol.7 (No.5). e36787. ISSN 1932-6203

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Official URL: http://dx.doi.org/10.1371/journal.pone.0036787

Abstract

Prolongation of pregnancy i.e. going more than 10 days over the estimated due date, complicates up to 10% of all pregnancies and is associated with increased risk to both mother and fetus. Despite the obvious need for contractions of the uterus to end pregnancy, there have been no studies directly examining the role of uterine smooth muscle, myometrium, in the aetiology of prolonged pregnancy. This study tested the hypothesis that the intrinsic contractile characteristics of myometrium taken from women with prolonged pregnancy (>41 weeks and 3 days) was reduced compared to those delivering at term (39–41 weeks). We recruited women undergoing Caesarean Section (CS) delivery either pre-labour (n = 27) or in labour (n = 66) at term or postdates. The contractile ability of the postdates myometrium, whether spontaneous or elicited by oxytocin or high-K solution, was significantly reduced compared to term myometrium. These differences remained when adjusted for parity and other maternal characteristics. The findings remained significant when expressed per cross sectional area. Histological examination revealed no differences between the two groups. The contractile differences were however related to intracellular Ca transients suggesting an effect of [Ca] on reduced force production in the postdates group. In summary, myometrium from prolonged pregnancies contracts poorly in vitro even when stimulated with oxytocin and in active labour. Responses to high K+ and measurements of Ca suggest that alterations in excitation contraction coupling, rather than any histological changes of the myometrium, may underlie the differences between term and postdates myometrium. We show that postdates pregnancy is associated with poor myometrial activity and suggest that this may contribute to increased myometrial quiescence and hence, prolonged gestation.

Item Type:

Journal Article

Subjects:

R Medicine > RG Gynecology and obstetrics

Divisions:

Faculty of Medicine > Warwick Medical School

Library of Congress Subject Headings (LCSH):

Prolonged pregnancy -- Etiology, Myometrium -- Physiology, Uterus -- Contraction

Journal or Publication Title:

PLoS One

Publisher:

Public Library of Science

ISSN:

1932-6203

Official Date:

2012

Dates:

Date	Event
2012	Published

Volume:

Vol.7

Number:

No.5

Page Range:

e36787

Identification Number:

10.1371/journal.pone.0036787

Status:

Peer Reviewed

Publication Status:

Published

Access rights to Published version:

Open Access

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