Abstract
Epidemiological evidence suggests that normal pregnancy in women is associated with decreased cardiovascular risk in later life. Clinical studies have provided evidence that alterations in vascular function and structure are detectable long after delivery. To understand these findings, we examined mesenteric artery reactivity at both early (3 days and 2–4 weeks) and late (12 weeks) postpartum (PP) time points in relation to late pregnancy (LP) and lactation. Vessels from virgin controls, LP, PP, and nursing and non-nursing mothers were tested for responses to phenylephrine (PE), high potassium solutions (high K+), and acetylcholine (ACh). Passive arterial distensibility, vessel dimensions, and collagen and elastin content were evaluated for the studied groups. We observed that (1) there was a significant inhibition of vascular reactivity to PE in LP, 3 days and 2 weeks PP vessels that returned to pre-pregnancy levels at 4 and 12 weeks PP; (2) inhibition of NO production in PP vessels restored PE-induced constriction to pre-pregnancy levels; (3) vasodilator responses to ACh were similar at all PP periods; (4) LP and early PP was associated with a persistent increase in arterial distensibility that correlates with a PP-induced reduction in wall collagen, and regressed to pre-conception levels at 12 weeks PP; (5) vessels from non-nursing PP mice demonstrated an increased PE reactivity, diminished responses to ACh, and reduced distensibility compared to breastfeeding mice. These studies provide a timeframe for mesenteric artery adaptations that occur during pregnancy and extend to the PP period, but which may be modified by PP events.
Highlights
Normal pregnancy is characterized by a marked maternal cardiovascular adaptation that is critical for fetal survival and development
EC50 values calculated for arteries from virgin controls were not significantly different from EC50 values obtained from vessels at early and late PP (Fig. 5Sd and 5Se)
Concentration-response data from different groups of mice were compared by two-way repeated measures ANOVA after passing the Normality Test (Shapiro-Wilk) and Equal Variance Test (Brown-Forsythe)
Summary
Normal pregnancy is characterized by a marked maternal cardiovascular adaptation that is critical for fetal survival and development. Systemic blood pressure and uterine and peripheral vascular resistance are reduced in part due to increased uterine and systemic vascular dilatation and compliance [1,2,3,4,5]. Some of these maternal adaptive changes may persist postpartum for an undefined period. Observations of increased cardiac output and decreased peripheral vascular resistance have been reported up to 1 year PP in women [8]. Peripheral vascular compliance remains increased and MAP is reduced 1 year after delivery in comparison to the pre-pregnancy state [9]. Complicated pregnancies such as pre-eclampsia, pre-term birth, gestational diabetes, and high multiparity are associated with increased risks for hypertension, stroke, and diabetes in later life [3, 7, 10,11,12,13,14,15,16]
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