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Refractive status during pregnancy in the United States: results from NHANES 2005-2008
Frances Wu1, Julie M Schallhorn1,2, Eugene A Lowry3,4
1Department of Ophthalmology, University of California, San Francisco, CA, USA.
Purpose:
Anecdotal reports of refractive changes in pregnancy are familiar to optometrists and ophthalmologists. Refractive stability during pregnancy has implications in both prescribing of refractive correction and candidacy for refractive surgery. This study aims to examine refractive status in a nationally representative sample of US pregnant women.
Methods:
The National Health and Nutrition Examination Survey (NHANES) is a weighted, stratified, cross-sectional survey of the US population conducted every 2 years. During 2005-2006 and 2007-2008, the exam included multiple ophthalmic tests including refraction, keratometry, and lensometry. Female participants aged 20-44 years with available vision examination data were included in the study. Subjects were excluded if best obtainable visual acuity was worse than 20/40 or there was prior history of cataract or refractive surgery. The primary outcome was defined as refractive change stratified by trimester of pregnancy.
Results:
301 pregnant women were matched with 301 nonpregnant controls based on age, ethnicity, and education. There was no difference in refractive error between pregnant women and matched nonpregnant controls (all p > 0.99). For the refractive change analysis, a subgroup of 60 pregnant subjects with glasses at presentation was matched to 60 nonpregnant controls. Multivariate regression showed a significant increase in refractive change versus prior to glasses prescription by trimester of pregnancy (p = 0.02), though this change was not in a specific direction (i.e., no significant shift toward either myopia or hyperopia).
Conclusions:
Pregnant women have greater refractive difference from prior spectacle prescription later in pregnancy, but the direction of this change is variable and not significant. This finding may reflect a longer time to last glasses prescription later in pregnancy, given concerns that refractive error fluctuates in pregnancy. Additional longitudinal studies are needed to better characterize the effects of pregnancy on refractive status.
