Pregnancy reduces, not increases, risk of myopia onset or progression
Pregnancy does not increase the risk of myopia, according to a recent study that demonstrated exactly the opposite, such that pregnant women have a lower risk of myopia onset or progression compared with their nonpregnant counterparts.
The study population comprised 10,401 women aged 20 to 50 years old from the SUN Project, a multipurpose, prospective and dynamic cohort of university graduates conducted in Spain. Followed for up to 14 years, the women completed questionnaires assessing pregnancy and refractive changes at baseline and biennially thereafter.
Results showed an inverse association between pregnancy and the risk of myopia development or progression during each of the 2-year periods over the follow-up, with a fully adjusted hazard ratio of 0.61 (95 percent CI, 0.49 to 0.75) after controlling for known potential confounders.
Researchers noted that the inverse association between pregnancy and risk of myopia progression might potentially be explained by the higher exposure to outdoor activities reported in pregnant women during their maternal leaves (time of outdoors physical activity, 6.9 vs 5.2 hours per week in nonpregnant women; p=0.002).
Researchers also pointed out that the influence of pregnancy on myopia progression demands special attention due to the high prevalence of myopia and its important socioeconomic consequences.
“Our findings, if confirmed by further studies, can be of great relevance today. The most common age of females who seek refractive surgery is between 20 and 30 years, and this age coincides with the period of their lives that they are most likely to get pregnant,” they said.
Changes that occur in the cardiovascular, hormonal, metabolic, hematologic and immunologic system during pregnancy are believed to have an impact on the ocular system. Previous data indicate that water retention during pregnancy induces changes on corneal thickness and curvature, and these changes could modify the corneal refractive index. Hormonal changes may also play a role, as progestins and oestrogens increase the permeability of the crystalline lens to water, thus reducing the refractive index. [Afr J Reprod Health 2008;12:185–196]