Stress During Pregnancy Increases Offspring's Risk of Asthma

A new study has found that maternal stress during pregnancy is associated with increased risk of asthma in their offspring.

It is always advised to avoid stress during pregnancy as any level of stress leads to negative outcomes for mothers as well as their infants. The negative outcomes include several developmental and behavioral problems. The new study, led by researchers at the Harvard School of Public Health, states that stress among pregnant mice led to elevated risk of allergy-induced asthma in their offspring.

The naturally occurring stress hormone - Glucocorticoids (GCs) - helps keep inflammation at low levels. The other synthetic versions of this hormone include prednisone, dexamethasone and hydrocortisone. These are most often used to treat allergic reactions.  However, the same glucocorticoids can cause inflammation and ramp-up allergic responses to irritants like air pollution or pollen. During normal pregnancy, the levels of GC are already high and the stage is set for a harmful allergic response in case the levels rise in response to stress.

The current study, led by Robert Lim, Alexey V. Fedulov and Lester Kobzik, looked at whether the rise in GC due to maternal stress during pregnancy triggered the development of asthma in the offspring. For this, they exposed one set of pregnant mice to a single bout of stress and the second set of mice to dexamethasone so as to replicate the effects of stressful occurrence. The third set of mice were given sufficient metyropone - a steroid inhibitor that curbs the release of stress hormone, to counteract the rise in stress hormone after exposure to stress and the fourth set of mice was part of a control group.

The researchers noticed that high levels of stress hormone in the mother can cross the placenta and rise fetal levels of CORT, eventually leading to higher chances of asthma and allergies. The offspring of all mice were exposed to allergens after birth.

Researchers explain, "Only the offspring of stressed mothers demonstrated increased asthma susceptibility compared with nonstressed mothers. We also demonstrated that a single episode of stress significantly elevated maternal stress hormone levels. These results indicate that maternal stress can play a role in the initiation of asthma by increasing asthma susceptibility in offspring."

The finding appears in the AJP: Lung Cellular and Molecular Physiology.