Researchers in Korea recently discovered associations between having kids and an increased risk of open-angle glaucoma (OAG), suggesting changes during pregnancy and delivery affect the development of the disease.

The study, recently published in the Journal of Glaucoma, included 1,798 postmenopausal women from the Korean National Health and Nutrition Examination Survey from 2010 to 2011. After performing a comprehensive eye exam and gathering information on demographics, comorbidities and health-related behaviors, researchers found the prevalence of OAG was 6.42%. They also found patients who had three or more deliveries were at increased risk of OAG compared with those who had two deliveries; however, two deliveries was not associated with a higher risk than one.

 “This might be because the optic disc can overcome small insults below a threshold, but the accumulation of multiple stressors could create an unfavorable environment around the optic nerve that crosses a certain threshold, initiating OAG,” the researchers said in the study.

The researchers believe hormonal changes and the effects of the birth process are both involved in the increased risk. Blood loss during delivery causes temporary systemic hypotension and decreased ocular perfusion, thus increasing the risk for glaucoma development or progression. In addition, increased oxytocin levels during labor can induce capillary constriction and decreases aqueous outflow, while stress during labor could induce the release of large amounts of epinephrine and norepinephrine, also increasing IOP.

 The study also found an independent association with younger age at first childbirth and a higher risk of OAG. Patients who were between the ages of 16 and 20, as well as 21 and 23, were at a higher risk of OAG compared with those ages 24 to 26 at first delivery.

 “Considering the fluctuations of hormone levels and physiology changes during pregnancy and after delivery, younger age at first delivery seems to be more stressful physiologically and neurophysiologically, which could affect the development of OAG,” the researchers said in the study.

 While the study highlights the role pregnancy and delivery play in the pathogenesis of glaucoma, further studies are needed to uncover the underlying mechanisms, the study concludes.