Purpose : Evaluation of the retinal vasculature during pregnancy has been limited due to concerns regarding the use of fluorescein dye and dilating drops. The purpose of this study was to use noninvasive optical coherence tomography angiography (OCT-A) to compare the retinal vasculature in third trimester high risk pregnancies to low risk pregnancies.

Methods : OCT-A imaging was performed on women at high risk for a complicated pregnancy course during the third trimester and compared with a control group of women who were at low risk for complicated pregnancies. Vessel perfusion density (PD) and vessel length density (VLD) of the superficial vascular plexus (SVP), intermediate capillary plexus (ICP), and the deep capillary plexus (DCP) were calculated in ImageJ per prior published technique. Seven zones in each layer were analyzed: 1) whole image (entire field of view); 2) fovea (circle centered on the fovea with 0.5mm radius); 3) parafovea (ring centered on the fovea with inner/outer radii of 0.5/1.5 mm); and 4-7) superior, inferior, nasal, and temporal inner macula subfields per the early treatment diabetic retinopathy study. Post-partum imaging at 2-6 months was performed on a subset of patients.

Results : 134 eyes in 78 women with high risk pregnancies and 16 eyes in 9 women with low risk pregnancies were imaged in the third trimester. The most common pregnancy risk factors were advanced maternal age, diabetes mellitus, and intrauterine growth restriction. Compared to low risk pregnancies, whole image SVP-PD and SVP-VLD in high risk pregnancies had significant reductions in perfusion (p<0.001 and p=0.025, respectively). Whole image ICP-PD and ICP-VLD also trended towards reductions in perfusion. Whole image DCP-PD and DCP-VLD trended towards increases in perfusion. Imaging was repeated in 6 eyes in 3 women with high risk pregnancies in the postpartum period. Postpartum imaging revealed a trend toward opposite perfusion changes in SVP-PD, SVP-VLD, DCP-PD, and DCP-VLD.

Conclusions : OCT-A can be used to safely and noninvasively characterize the retinal vasculature during pregnancy. Relative to low risk pregnancies, high risk pregnancies experience significant reductions in vascular perfusion in the SVP-PD and SVP-VLD. Further studies may be warranted to better characterize the effect of risk factors on retinal vasculature perfusion and if perfusion changes are reversed with delivery.