Magnesium sulfate has sex-specific, dose-dependent vasodilator effects on preterm placental vessels

Women's Health Across the Lifespan: A Sex- and Gender-Focused Perspective

Women's health in physical therapy has historically focused on sexual and reproductive health. The biological and social constructs of sex and gender, respectively, are determinants of health, including pathophysiology of disease and therapeutic outcomes, and an expansion of the concept of "women's health" is warranted. This Perspective explores the role of sex and gender as key determinants of women's and girls' health and highlights the factors pertinent to physical therapist practice. The Scale for the Assessment for Narrative Review Articles (SANRA), a 6-point assessment to evaluate the quality of narrative reviews, was used a priori and consulted throughout. Across the lifespan, sex- and gender-based health disparities exist. These include sex-based disparities in maternal-fetal outcomes linking female fetal sex to maternal hypertensive disorders of pregnancy, along with a sex-based female advantage in birth outcomes and the emergence of gender differences in motor development. A complex interplay of biological and socially influenced factors contributes to an increased care burden for women throughout adulthood and specific risks for the development of cardiovascular and pelvic floor conditions, decreased function, and increased disability. Sex- and gender-disaggregated data are lacking in outcomes literature. A sex- and gender-informed approach in physical therapy, including analyzing data by sex and gender, may better meet the needs of patients and better prepare physical therapist professionals to contribute to women's health across the lifespan. Success will take coordinated effort involving many stakeholders within and adjacent to the physical therapist community. The influence of sex and gender are lifelong determinants of health, making them critically important to consider in physical therapist practice, education, research, advocacy, and policy. In women's health, focusing on sexual and reproductive health is limiting and insufficient.

Antenatal Magnesium Sulfate Benefits Female Preterm Infants but Results in Poor Male Outcomes

Magnesium sulfate (MagSul) is used clinically to prevent eclamptic seizures during pregnancy and as a tocolytic for preterm labor. More recently, it has been implicated as offering neural protection in utero for at-risk infants. However, evidence is mixed. Some studies found that MagSul reduced the incidence of cerebral palsy (CP) but did not improve other measures of neurologic function. Others did not find any improvement in outcomes. Inconsistencies in the literature may reflect the fact that sex effects are largely ignored, despite evidence that MagSul shows sex effects in animal models of neonatal brain injury. The current study used retrospective infant data to assess differences in developmental outcomes as a function of sex and MagSul treatment. We found that on 18-month neurodevelopmental cognitive and language measures, preterm males treated with MagSul (n = 209) had significantly worse scores than their untreated counterparts (n = 135; p < 0.05). Female preterm infants treated with MagSul (n = 220), on the other hand, showed a cognitive benefit relative to untreated females (n = 123; p < 0.05). No significant effects of MagSul were seen among females on language (p > 0.05). These results have tremendous implications for risk-benefit considerations in the ongoing use of MagSul and may explain why benefits have been hard to identify in clinical trials when sex is not considered.

Magnesium Sulfate-Mediated Vascular Relaxation and Calcium Channel Activity in Placental Vessels Different From Nonplacental Vessels

Background

Magnesium sulfate (MgSO₄) has been used as a common therapy for preeclampsia and eclampsia for many years. MgSO₄ decreases peripheral vascular resistance so as to reduce maternal blood pressure. Whether placental blood vessels react to MgSO₄ in the same patterns as that in maternal vessels is largely unknown.

Methods and Results

This study compared placental vessels (PV) versus nonplacental vessels (non‐PV) in human and animal models. MgSO₄‐caused vascular dilation was significantly weaker in PV than that in non‐PV. Prostaglandin I₂ synthetase affected MgSO₄‐mediated vasodilatation in PV, not in umbilical vessels, while cyclooxygenase did not influence MgSO₄‐induced relaxation in both PV and non‐PV. Mg²⁺‐caused vasodilatation was mainly through calcium channels. In PV, calcium channel activities were significantly weaker in PV than that in non‐PV. Relative mRNA expression of CACNA1D,CACNB2, and CACNB3 was significantly higher in PV than those in umbilical vessels, despite the fact that the expression of CACNA1F was less in PV. The contractile phenotype of smooth muscle cell marker (CALD1) was less and the synthetic phenotype (MYH10) was more in PV than that in UV.

Conclusions

These results demonstrated that PV were characterized by much weaker responses to MgSO₄ compared with nonplacental vessels. The difference was related to weaker calcium channel activity and minor contractile phenotype smooth muscle cells in PV, providing important information for further understanding treatments with MgSO₄ in preeclampsia.

Effect of Fetal Sex on Maternal and Obstetric Outcomes

Fetal sex plays an important role in modifying the course and complications related to pregnancy and may also have an impact on maternal health and well-being both during and after pregnancy. The goal of this article is to review and summarize the findings from published research on physiologic and pathologic changes that may be affected by fetal sex and the effect of these changes on the maternal and obstetrical outcomes. This will help create awareness that fetal sex is not just a random chance event but an interactive process between the mother, the placenta, and the fetus. The reported effects of male sex on the course of pregnancy and delivery include higher incidence of preterm labor in singletons and twins, failure of progression in labor, true umbilical cord knots, cord prolapse, nuchal cord, higher cesarean section rate, higher heart rate variability with increased frequency, and duration of decelerations without acidemia and increased risk of gestational diabetes mellitus through the poor beta cells function. Similarly, female fetal sex has been reported to modify pregnancy and delivery outcomes including altered fetal cardiac hemodynamics, increased hypertensive diseases of pregnancy, higher vulnerability of developing type 2 DM after pregnancy possibly because of influences on increased maternal insulin resistance. Placental function is also influenced by fetal sex. Vitamin D metabolism in the placenta varies by fetal sex; and the placenta of a female fetus is more responsive to the relaxing action of magnesium sulfate. Male and female feto-placental units also vary in their responses to environmental toxin exposure. The association of fetal sex with stillbirths is controversial with many studies reporting higher risk of stillbirth in male fetuses; although some smaller and limited studies have reported more stillbirths with female fetus pregnancies. Maternal status such as BMI may in turn also affect the fetus and the placenta in a sex-specific manner. There is probably a sex-specific maternal-placental-fetal interaction that has significant biological implications of which the mechanisms may be genetic, epigenetic, or hormonal. Determination of fetal sex may therefore be an important consideration in management of pregnancy and childbirth.