Hypertension disorders during pregnancy can be dangerous. Women who suffer from high blood pressure may develop preeclampsia or eclampsia. Too much protein is excreted through the kidneys. As a result, the placenta may detach and/or the child may be delivered prematurely. In severe cases, the mother may suffer a cerebral hemorrhage, kidney failure or a ruptured liver. Many factors can contribute to high blood pressure and even affect the child’s future health. New research has found that the humidity and temperature outdoors during pregnancy could affect the future blood pressure of the unborn child.
How Humidity and Temperature Affect Blood Pressure in Childhood
A study from the University of Bristol has shown that exposure to relative humidity and temperature levels during pregnancy is linked to changes in blood pressure in children. Higher relative humidity in pregnancy has been associated with a steeper increase in blood pressure, and prenatal exposure to higher temperatures with a slower increase in blood pressure, particularly in childhood from ages 3 to 10 years. Although an increase in blood pressure is normal in this age range, these weather-related factors have been associated with a different rate of increase, particularly in childhood.
In previous studies, blood pressure was usually only measured at a single time point, focusing on individual exposures, particularly air pollution. In this study, researchers examined the association between a range of prenatal urban environmental exposures and changes in systolic and diastolic blood pressure from childhood to early adulthood using repeated blood pressure measurements.
The study analyzed repeated blood pressure measurements in over 7,000 participants aged between 3 and 24 years from the Bristol Children of the 90s Study, a world-leading longitudinal study, to examine the association between various features of the urban environment in pregnancy and blood pressure from childhood to early adulthood. The analyzes were repeated in four independent European cohorts with over 9,000 individuals in Finland, France and the Netherlands.
The research team examined 43 different measures of noise, air pollution, the built environment, natural areas, traffic, meteorology and unhealthy diet and found that prenatal outdoor temperature and humidity can influence changes in blood pressure, particularly in childhood.
Overall, the study showed that higher humidity was associated with a faster rise and higher temperature with a slower rise in systolic blood pressure in childhood. Higher humidity has been linked to a faster increase in diastolic blood pressure in childhood. In the UK cohort, higher levels of air pollution were associated with a faster rise in diastolic blood pressure in childhood and a slower rise in adolescence, but this association was not replicated in other cohorts. There was little evidence of an association between other urban environmental exposures and changes in systolic or diastolic blood pressure.
Children with high blood pressure are more likely to have higher blood pressure as adults, which can increase the risk of heart disease and stroke, as well as kidney disease and vascular dementia. Further work is needed to understand how weather-related conditions during pregnancy may affect the child’s blood pressure so that strategies can be developed to prevent cardiovascular disease in later adulthood related to prenatal environmental exposures.
The Role of Folic Acid
It is well known that folic acid is important for a healthy pregnancy. However, there is also increasing evidence that maternal nutrition during pregnancy may also influence the cardiometabolic health of the offspring through its effects on the intrauterine environment of the fetus. Folate is involved, among other things, in nucleic acid synthesis, gene expression and cell growth. Citrus juices and dark green vegetables are good sources of folic acid.
Research suggests that higher maternal folic acid levels may help counteract the adverse associations between maternal cardiometabolic risk factors and the child’s systolic blood pressure. In fact, in young adults, higher folic acid intake has been associated with a lower incidence of hypertension later in life. These results suggest that early risk assessment and intervention before conception and during pregnancy could lead to new ways to prevent hypertension and its consequences across the lifespan and across generations.