Retinal Layer Thinning During Pregnancy May Foretell Adverse Outcomes

The inner superior ganglion cell layer (GCL) is thinner in patients with high-risk pregnancies who go on to have obstetrical complications, according to a study published  in the Journal Français d’Ophtalmologie. The study suggests that individuals with preexisting vascular risk factors may display retinal thinning even before pregnancy.

The prospective study enrolled 32 women (age range, 18-45 years), 15 of whom developed an adverse outcome — hypertension linked to pregnancy, preeclampsia, preeclampsia-related maternal organ dysfunction, or preterm delivery — and 17 with uncomplicated pregnancies. Women received care at a large university-affiliated hospital in Israel, from January 2017 to May 2018. The analysis excluded patients with gestation shorter than 24 weeks, history of conditions such as chronic hypertension, or diabetes before pregnancy. Three participants were excluded for subretinal or intraretinal fluid. 

Preterm birth was the most frequently-experienced adverse outcome — participants in the complex pregnancy group delivered, on average, more than 3 weeks earlier than 37 weeks of gestation, compared with uncomplicated pregnancies (P =.005), and almost 50% of early high-risk patient deliveries required cesarean sections. 

Prenatal ocular testing involved nondilated, fovea-centered swept-source OCT. Individuals who developed an adverse outcome exhibited thinner macular inner superior ganglion cell layer (GCL) thickness, 84.5±6.9 µm compared with low-risk participants, 89.5±6.1 µm (P =.04), as well as total inner superior layer measurement of 295.5±39.1 µm, compared with 302.5±12.7 µm for those with uncomplicated pregnancies (P =.03). Inferior retinal layer volume was also thinner, 289.0±13.9 µm for those with higher obstetrical risk, compared with the normal cohort measuring 301.0±17.1 µm (P =.03). Total macular measurement was 7.5±0.3 mm³ for those with subsequent complications, as opposed to 7.7±0.3 mm³ in the low-risk group (P =.02).

In addition to potential prediction of obstetrical risk levels, retinal thinning may also signal lasting secondary consequences for patients’ eyes. “Long-term ophthalmologic follow-up for women who experienced high-risk pregnancy may be necessary,” the researchers advise.

Previous studies have compared high and low risk maternal retinal volume, with results varying from retinal thickening in high-risk pregnancies, to thinning or comparable thicknesses. Some analyses included individuals with subretinal or intraretinal fluid, which increases the total measurement. 

GCL thinning can be prompted by high systolic blood pressure, the researchers explain. They added that osmotic and vitreous volume changes in pregnancy may also lead to thinning of the “most superficial nuclear layer.” Additionally, cytokines upregulated with preeclampsia have been shown to disrupt ganglion cell metabolism. Retinal changes have been revealed in pre-clinical diabetes, and with chronic hypertension. Investigators note vascular disorders that thin retinal layers may concurrently be associated with disorders that trigger high-risk pregnancies.

“Vascular conditions associated with retinal thinning should be kept in mind, for such conditions could also be risk factors for developing obstetric complications,” according to the researchers. “This would mean that women with preexisting vascular risk factors would display retinal thinning even before pregnancy.”

Limitations of this investigation include a relatively small cohort, as well as no analysis of intraocular pressure (IOP) changes. Strengths comprised the exclusion of those with baseline fluids, as this factor could influence retinal thickness.