Blood pressure changes during pregnancy

Elevated gestational testosterone impacts vascular and uteroplacental function

Maternal vascular adaptations to establish an adequate blood supply to the uterus and placenta are essential for optimal nutrient and oxygen delivery to the developing fetus in eutherian mammals, including humans. Numerous factors contribute to maintaining appropriate hemodynamics and placental vascular development throughout pregnancy. Failure to achieve or sustain these pregnancy-associated changes in women is strongly associated with an increased risk of antenatal complications, such as preeclampsia, a hypertensive disorder of pregnancy. The precise etiology of preeclampsia is unknown, but emerging evidence points to a potential role for androgens. The association between androgens and maternal cardiovascular and placental function merits particular attention due to the notable 2- to 3-fold elevated plasma testosterone (T) levels observed in preeclampsia. T levels in preeclamptic women positively correlate with vascular dysfunction, and preeclampsia is associated with increased androgen receptor (AR) levels in placental tissues. Moreover, animal studies replicating the pattern and magnitude of T increase observed in preeclamptic pregnancies have reproduced key features of preeclampsia, including gestational hypertension, endothelial dysfunction, heightened vasoconstriction to angiotensin II, impaired spiral artery remodeling, placental hypoxia, reduced nutrient transport, and fetal growth restriction. Collectively, these findings suggest that AR-mediated activity plays a significant role in the clinical presentation of preeclampsia. This review critically evaluates this hypothesis, considering both clinical and preclinical evidence.

Correlations of spot urinary sodium and potassium with blood pressure in pregnant women: A longitudinal study in Southern Thailand

OBJECTIVE

To assess the changes of spot urinary sodium and potassium and blood pressure (BP) throughout pregnancy and their correlations in southern Thailand.

METHODS

A longitudinal study was conducted in southern Thailand from March 2018 to November 2019. Spot urinary excretion of sodium per creatinine (U[Na⁺ ]/[Cr]), potassium per creatinine (U[K⁺ ]/[Cr]) and U[Na⁺ ]/[K⁺ ] ratios, and BP were measured at four time points throughout pregnancy. A one-way analysis of variance with repeated measures and Bonferroni correction with post hoc analysis was used to identify significant differences between time points. The correlations were measured using Pearson's correlation coefficients.

RESULTS

A total of 327 pregnant women were included. Both systolic and diastolic BPs decreased gradually from up to 14 weeks of pregnancy to 18-22 weeks and then increased until 30-34 weeks. Mean spot U[Na⁺ ]/[Cr] ratios did not significantly change during the study period. Mean spot U[K⁺ ]/[Cr] ratios gradually increased, and spot U[Na⁺ ]/[K⁺ ] ratios gradually decreased. The correlation of spot U[Na⁺ ]/[Cr] and U[K⁺ ]/[Cr] ratios with BPs was weakly negative at all four time points.

CONCLUSIONS

Spot U[Na⁺ ]/[Cr] and U[K⁺ ]/[Cr] ratios are inversely correlated with BPs; weak correlations are found among pregnant women in southern Thailand. Further research in different populations is required to confirm its correlation and broader use.

Comparison among research, home, and office blood pressure measurements for pregnant women: The TMM BirThree Cohort Study

Blood pressure (BP) measurements of pregnant women have been collected in offices and at home for previous research. However, it remains uncertain whether there is difference between research BP, defined as BP measured for the purpose of epidemiological research and BP measured at home or in an office. Therefore, the present study aimed to compare research BP with home and unstandardized office BP. Research, home, and office BP were measured among pregnant women who participated in the Tohoku Medical Megabank Project Birth and Three-Generation Cohort Study (TMM BirThree Cohort Study). Research BP was measured twice at our research center while the participant was seated and after resting for 1-2 minutes. Research, home, and office BP were compared and agreement among the values was assessed. Differences among research, home, and office BP values and possible factors affecting differences were analyzed. Among 656 pregnant women, the mean (± standard deviations) research systolic (S), diastolic (D) BP, home SBP, home DBP office SBP, and office DBP were 103.8 ± 8.5, 61.8 ± 7.3, 104.4 ± 9.2, 61.2 ± 6.8, 110.5 ± 10.8, and 63.8 ± 8.7mmHg, respectively. Research SBP value was lower than home value (P = .0072; difference between mean research and home BP: -0.61 ± 7.8 mmHg). Research SBP and DBP values were lower than office values (P < .0001 for both SBP and DBP; means ± standard deviations of differences between research and office BP: 6.7 ± 10.1 and 2.0 ± 8.5 mmHg for SBP and DBP, respectively). In conclusion, when research BP is measured under conditions controlled, research BP can give close values to home BP for pregnant women.

Hypoxia-induced small extracellular vesicle proteins regulate proinflammatory cytokines and systemic blood pressure in pregnant rats

Small extracellular vesicles (sEVs) released from the extravillous trophoblast (EVT) are known to regulate uterine spiral artery remodeling during early pregnancy. The bioactivity and release of these sEVs differ under differing oxygen tensions and in aberrant pregnancy conditions. Whether the placental cell-derived sEVs released from the hypoxic placenta contribute to the pathophysiology of preeclampsia is not known. We hypothesize that, in response to low oxygen tension, the EVT packages a specific set of proteins in sEVs and that these released sEVs interact with endothelial cells to induce inflammation and increase maternal systemic blood pressure. Using a quantitative MS/MS approach, we identified 507 differentially abundant proteins within sEVs isolated from HTR-8/SVneo cells (a commonly used EVT model) cultured at 1% (hypoxia) compared with 8% (normoxia) oxygen. Among these differentially abundant proteins, 206 were up-regulated and 301 were down-regulated (P < 0.05), and they were mainly implicated in inflammation-related pathways. In vitro incubation of hypoxic sEVs with endothelial cells, significantly increased (P < 0.05) the release of GM-CSF, IL-6, IL-8, and VEGF, when compared with control (i.e. cells without sEVs) and normoxic sEVs. In vivo injection of hypoxic sEVs into pregnant rats significantly increased (P < 0.05) mean arterial pressure with increases in systolic and diastolic blood pressures. We propose that oxygen tension regulates the release and bioactivity of sEVs from EVT and that these sEVs regulate inflammation and maternal systemic blood pressure. This novel oxygen-responsive, sEVs signaling pathway, therefore, may contribute to the physiopathology of preeclampsia.

Reference ranges and trajectories for blood pressure in pregnancy: findings from a follow-up study based on China Maternal and Newborn's Health Monitoring System

Objectives: This study aimed to establish normal blood pressure reference ranges across gestation and maternal characteristics.Methods: We conducted a follow-up study including 29,200 Chinese normal pregnant women. Multilevel restrictive cubic spline models were used to calculate normal blood pressure reference ranges among all population and stratified groups.Results: In all normal pregnancies, the normal reference range of systolic blood pressure were 93.94-118.74 mmHg(2.5^th-97.5^th) and 97.35-124.63 mmHg at 12 and 37 weeks gestation, respectively while 58.79-74.21 mmHg and 59.19-78.25 mmHg were for diastolic blood pressure at 12 and 37 weeks gestation, which differed in subgroups stratified by prepregnancy body mass index and maternal age.Conclusion: This study provides evidence for blood pressure management in Chinese pregnant women.

Androgens in maternal vascular and placental function: implications for preeclampsia pathogenesis

Adequate maternal vascular adaptations and blood supply to the uterus and placenta are crucial for optimal oxygen and nutrient transport to growing fetuses of eutherian mammals, including humans. Multiple factors contribute to hemodynamics and structuring of placental vasculature essential for term pregnancy with minimal complications. In women, failure to achieve or sustain favorable pregnancy progression is, not surprisingly, associated with high incidence of antenatal complications, including preeclampsia, a hypertensive disorder of pregnancy. While the pathogenesis of preeclampsia in women remains unknown, a role for androgens is emerging. The relationship between androgens and maternal cardiovascular and placental function deserves particular consideration because testosterone levels in the circulation of preeclamptic women are elevated approximately two- to three-fold and are positively correlated with vascular dysfunction. Preeclampsia is also associated with elevated placental androgen receptor (AR) gene expression. Studies in animal models mimicking the pattern and level of increase of adult female testosterone levels to those found in preeclamptic pregnancies, replicate key features of preeclampsia, including gestational hypertension, endothelial dysfunction, exaggerated vasoconstriction to angiotensin II, reduced spiral artery remodeling, placental hypoxia, decreased nutrient transport and fetal growth restriction. Taken together, these data strongly implicate AR-mediated testosterone action as an important pathway contributing to clinical manifestation of preeclampsia. This review critically addresses this hypothesis, taking into consideration both clinical and preclinical data.

Testosterone alters maternal vascular adaptations: role of the endothelial NO system

Sex steroid hormones estradiol and progesterone play an important role in vascular adaptations during pregnancy. However, little is known about the role of androgens. Plasma testosterone (T) levels are elevated in preeclampsia, mothers with polycystic ovary, and pregnant African American women, who have endothelial dysfunction and develop gestational hypertension. We tested whether increased T alters vascular adaptations during pregnancy and whether these alterations depend on endothelium-derived factors, such as prostacyclin, endothelium-derived hyperpolarizing factor, and NO. Pregnant Sprague Dawley rats were injected with vehicle (n=12) or T propionate [0.5 mg/Kg per day from gestation day 15-19; n=12] to increase plasma T levels 2-fold, similar to that observed in preeclampsia. Telemetric blood pressures and endothelium-dependent vascular reactivity were assessed with wire-myograph system. Phospho-endothelial NO synthase and total endothelial NO synthase were examined in mesenteric arteries. Mean arterial pressures were significantly higher starting from gestation day19 until delivery in T-treated dams. Endothelium-dependent relaxation responses to acetylcholine were significantly lower in mesenteric arteries of T-treated dams (pD(2) [-log EC(50)]=7.05±0.06; E(max)=89.4±1.89) compared with controls (pD(2)=7.38±0.04; E(max)=99.9±0.97). Further assessment of endothelial factors showed NO-mediated relaxations were blunted in T-treated mesenteric arteries (E(max)=42.26±5.95) compared with controls (E(max)=76.49±5.06); however, prostacyclin- and endothelium-derived hyperpolarizing factor-mediated relaxations were unaffected. Relaxation to sodium nitroprusside was unaffected with T-treatment. Phosphorylations of endothelial NO synthase at Ser(1177) were decreased and at Thr(495) increased in T-treated mesenteric arteries without changes in total endothelial NO synthase levels. In conclusion, increased maternal T, at concentrations relevant to abnormal clinical conditions, cause hypertension associated with blunting of NO-mediated vasodilation. T may induce the increased vascular resistance associated with pregnancy-induced hypertension.

Blood pressure measured in the clinic and at home during pregnancy among nulliparous and multiparous women: the BOSHI study

BACKGROUND

Hypertension during pregnancy can cause serious problems during delivery, such as stroke, premature delivery, or low birthweight. Nulliparity is believed to be a risk factor for hypertension during pregnancy. However, the relationship between parity and blood pressure determined at home during pregnancy is still unknown.

METHODS

We assessed the incidence of gestational hypertension or preeclampsia in 575 nulliparous and multiparous women. Also, we examined blood pressure measured in the clinic and at home among 530 normotensive pregnant women who received antenatal care at a maternity hospital in Japan. Clinic blood pressures (CBPs) were obtained by duplicate measurement at each antenatal care visit. The participants were also required to measure their own blood pressures every morning at home while they were pregnant. A linear mixed model was used for analysis of the blood pressure course throughout pregnancy.

RESULTS

A total of 315 nulliparous and 215 multiparous women were entered into this study (mean age, 30.1 ± 4.6 years and 33.0 ± 4.1 years, respectively). CBP levels during pregnancy among nulliparous women were significantly higher than among multiparous women (P = 0.02/P <0.0001 for systolic/diastolic blood pressure), whereas there were no significant differences in home blood pressure (HBP) levels during pregnancy between the two groups (P = 0.4/P = 0.2 for systolic/diastolic blood pressure).

CONCLUSIONS

HBP levels during pregnancy were shown not to differ between nulliparous and multiparous women, while CBP levels during pregnancy were higher among nulliparous than among multiparous women.