HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 293/3/R1280    most recent 00342.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via ISI Web of Science (1) Citing Articles via Google Scholar Google Scholar Articles by Bennet, L. Articles by Gunn, A. J. Search for Related Content PubMed PubMed Citation Articles by Bennet, L. Articles by Gunn, A. J.

DEVELOPMENTAL PHYSIOLOGY AND PREGNANCY

Male disadvantage? Fetal sex and cardiovascular responses to asphyxia in preterm fetal sheep

Department of Physiology, The University of Auckland, Auckland, New Zealand

Submitted 15 May 2007 ; accepted in final form 21 June 2007

Clinically and experimentally male fetuses are at significantly greater risk of dying or suffering injury at birth, particularly after premature delivery. We undertook a retrospective cohort analysis of 60 female and 65 male singleton preterm fetal sheep (103–104 days, 0.7 gestation) with mean arterial blood pressure (MAP), heart rate, and carotid and femoral blood flow recordings during 25 min of umbilical cord occlusion in utero. Occlusions were stopped early if fetal MAP fell below 8 mmHg or if there was asystole for >20 s. Fetuses that were able to complete the full 25-min period of occlusion showed no differences between sexes for any cardiovascular responses. Similar numbers of occlusions were stopped early in males (mean: 21 min, n = 16) and females (mean: 23 min, n = 16); however, they showed different responses. Short-occlusion males (n = 16) showed a slower initial fall in femoral vascular conductance, followed by greater bradycardia, hypotension, and associated organ hypoperfusion compared with full-occlusion fetuses. In contrast, short-occlusion females (n = 16) showed a significantly more rapid early increase in femoral vascular conductance than the full-occlusion fetuses, followed by worsening of bradycardia and hypotension that was intermediate to the full-occlusion fetuses and short-occlusion males. Among all fetuses, MAP at 15 min of occlusion, corresponding with the time of the maximal rate of fall, was correlated with postmortem weight in males (R² = 0.07) but not females. In conclusion, male and female fetuses showed remarkably similar chemoreflex and hemodynamic responses to severe asphyxia, but some males did show impaired hemodynamic adaptation within the normal weight range.

cardiovascular chemoreflex