Key result
Pregnancy was associated with a higher muscle sympathetic nerve activity burst frequency compared to non-pregnant controls (MD 10.6 bursts/min; 95% CI 7.2-14.0).
Why the study?
The study was conducted to quantify the impact of healthy and complex pregnancy on muscle sympathetic nerve activity at rest and in response to stress.
Does pregnancy alter muscle sympathetic nerve activity compared to non-pregnant individuals?
Meta-Analysis (n=807)
Does pregnancy alter muscle sympathetic nerve activity compared to non-pregnant individuals?
Mean Difference: 10.6 (95% CI 7.2–14)
Pregnancy is associated with increased muscle sympathetic nerve activity, which is further augmented in certain pregnancy complications such as obesity, obstructive sleep apnea, and gestational hypertension.
May elevate cardiovascular risk in pregnancy; leaves open causal role in complications and need for prospective trials.
We conducted a systematic review and meta‐analysis to quantify the impact of healthy and complex pregnancy on muscle sympathetic nerve activity (MSNA) at rest, and in response to stress. Structured searches of electronic databases were performed until February 23, 2022. All study designs (except reviews) were included: population (pregnant individuals); exposures (healthy and complicated pregnancy with direct measures of MSNA); comparator (individuals who were not pregnant, or with uncomplicated pregnancy); and outcomes (MSNA, BP, and heart rate). Twenty‐seven studies (N = 807) were included. MSNA burst frequency was higher in pregnancy (n = 201) versus non‐pregnant controls (n = 194) (Mean Differences [MD], MD: 10.6 bursts/min; 95% CI: 7.2, 14.0; I2 = 72%). Accounting for the normative increase in heart rate with gestation, burst incidence was also higher during pregnancy (Pregnant N = 189, non‐pregnant N = 173; MD: 11 bpm; 95% CI: 8, 13 bpm; I2 = 47%; p < 0.0001). Meta‐regression analyses confirmed that although sympathetic burst frequency and incidence are augmented during pregnancy, this was not significantly associated with gestational age. Compared to uncomplicated pregnancy, individuals with obesity, obstructive sleep apnea, and gestational hypertension exhibited sympathetic hyperactivity, while individuals with gestational diabetes mellitus or preeclampsia did not. Uncomplicated pregnancies exhibited a lesser response to head‐up tilt, but an exaggerated sympathetic responsiveness to cold pressor stress compared to non‐pregnant individuals. MSNA is higher in pregnant individuals and further increased with some, but not all pregnancy complications. PROSPERO registration number: CRD42022311590.
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Greenwall et al. (2023) conducted a meta-analysis in Pregnancy (n=807). Pregnancy (healthy and complicated) vs. Non-pregnant individuals or uncomplicated pregnancy was evaluated on MSNA burst frequency (MD 10.6 bursts/min, 95% CI 7.2, 14.0). Pregnancy was associated with a higher muscle sympathetic nerve activity burst frequency compared to non-pregnant controls (MD 10.6 bursts/min; 95% CI 7.2-14.0).
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