Fetomaternal Acid–Base Balance and Electrolytes during Pregnancy

Association of maternal mineral status with the risk of preterm birth: a retrospective cohort study

Background

There has been a gradual increase in the proportion of preterm birth in China during the past several decades. Maternal malnutrition is a significant determinant for preterm birth. Nevertheless, comprehensive studies investigating serum mineral levels during pregnancy associated with preterm birth remain scarce. This study aims to assess the associations between maternal serum mineral levels and the risk of preterm birth.

Methods

This retrospective cohort study of 18,048 pregnant women used data from a tertiary hospital in China from January 2016 to December 2022. Demographic data and serum mineral concentrations in the second and third trimesters of mothers were collected from the hospital information system. Analysis was performed using restricted cubic splines and logistic regression models.

Results

The proportion of preterm birth in this study was 6.01%. Phosphorus [P for overall = 0.005; P for nonlinear = 0.490; OR (95%CI) = 1.11 (1.04, 1.18)] and chlorine [P for overall = 0.002; P for nonlinear = 0.058; OR (95%CI) = 1.11 (1.03, 1.19)] showed a significant positive correlation with preterm birth in a linear fashion. Furthermore, serum levels of potassium (P for nonlinear <0.001), sodium (P for nonlinear = 0.004), and magnesium (P for nonlinear <0.001) exhibited non-linear relationships with the risk of preterm birth.

Conclusion

Serum levels of some minerals during pregnancy were associated with the risk of preterm birth among pregnant women. In addition to commonly recognized micronutrients such as folic acid, iron, and vitamin D, healthcare providers should also pay attention to the levels of these minerals during pregnancy.

A chirality-sensitive approach to predict chemical transfer across the human placental barrier

The placenta is a membrane that separates the fetus from the maternal circulation, and in addition to protecting the fetus, plays a key role in fetal growth and development. With increasing drug use in pregnancy, it is imperative that reliable models of estimating placental permeability and safety be established. In vitro methods and animal models such as rodent placenta are limited in application since the species-specific nature of the placenta prevents meaningful extrapolations to humans. In this regard, in silico approaches such as quantitative structure-property relationships (QSPRs) are useful alternatives. However, despite evidence that drug transport across the placenta is stereoselective (i.e., governed by the spatial arrangement of the atoms in a molecule), many QSPR models for placental transfer have been built using 2D descriptors that do not account for chirality and stereochemistry. In this study, we apply a chirality-sensitive and proven QSPR methodology titled "EigenValue ANalySis" (EVANS) to build QSPR models for placental transfer. We deploy EVANS along with robust machine learning algorithms to build (i) regression models on a dataset of environmental chemicals (dataset PD I) followed by (ii) classification models on a set of drug-like compounds (dataset PD II). The best models were found to achieve state-of-the-art performance, with the support vector machine algorithm returning rtrain2=0.85,rtest2=0.75 for PD I, and the logistic regression algorithm giving accuracy 0.88 and F1 score 0.93 for PD II. The best models were interpreted with the Shapley Additive Explanations paradigm, and it was found that autocorrelation descriptors are crucial for modelling placental permeability. In conclusion, we demonstrate the need of a chirality-sensitive approach for modelling placental transfer of chemicals, and present two predictive QSPR models that may reliably be used for prediction of placental transfer.

A Case of Recurrent Gestational Hypokalemia Due to an Exaggerated Physiological Response to Pregnancy: The Importance of Using Pregnancy-Specific Reference Ranges

Hypokalemia in pregnancy can occur secondary to hemodilution of pregnancy, physiological changes during pregnancy, or other pathological conditions. It should be investigated the same way as in non-pregnancy with particular emphasis on the importance of using pregnancy-specific reference ranges when interpreting clinical laboratory test results. Here, we present a case of a woman who had late-trimester gestational hypokalemia requiring potassium supplementation affecting four consecutive pregnancies. We thought that there was accompanying hypomagnesemia and hypobicarbonatemia in previous pregnancies, so we suspected a form of renal tubular dysfunction exacerbated by pregnancy. Subsequent investigation and the use of pregnancy-specific reference ranges revealed that this was an exaggerated physiological response to pregnancy.

Respiratory Acid-Base Disorders

Respiratory acid-base disorders are often not thought of as frequently as their metabolic cousins, which occur more frequently in the emergency department. Although most respiratory and acid-base disturbances are driven by lung pathology, central nervous system and other organ systems can and do play a role as well. Although managing the airway and appropriate mechanical ventilation may be necessary, it is akin to placing a band-aid on a large wound. It is crucial for the emergency clinician to discover the etiology of the disturbance as management depends on treating the underlying etiology to prevent worsening acid-base status.