August 10, 2017, Moran Eye Center, University of Utah Health, Salt Lake City, Utah.
In a study released today in JAMA Ophthalmology, Moran Eye Center Director of Pediatric Retina, Mary Elizabeth Hartnett, MD; Julia Shulman, MD, New York Medical College, Valhalla; and colleagues study preeclampsia as a risk or a protective factor in retinopathy of prematurity (ROP).
The role of preeclampsia in ROP continues to be controversial, but Moran's Mary Elizabeth Hartnett, MD, is tracking it down.
Preeclampsia, a high blood pressure condition in pregnant women, can lead to decreased blood flow to the placenta. If left untreated, it can be fatal. Both preeclampsia and ROP are linked to premature birth. Some studies suggest that preeclampsia is an increased risk for ROP, while others suggest it has protective effects on ROP.
"Only premature infants develop ROP. In ROP, blood vessels in the retina grow outside of their normal space. This can lead to blindness. The more premature the infant, the more likely the infant is to develop ROP and the more severe the ROP may be, said Hartnett. "We also know there is an association between premature birth and preeclampsia. This linkage makes it difficult to discern the effect of preeclampsia on risk of ROP."
The goal of this study was to address conflicting literature. Researchers analyzed preterm, low-birth-weight infants and full-term infants born to mothers who had preeclampsia or mothers who did not. They reviewed 290,992 live births in Utah from January 1 through December 31, 2010. They then performed similar analyses on a subset of the entire group, this time of only premature infants.
Results of this study show that in the full-term infants, preeclampsia was a risk factor for ROP and for severe ROP. However, when researchers analyzed only infants with premature birth, preeclampsia appeared protective.
Why the conflicting results? The authors believe that a plausible interpretation for the conflicting results is that maternal preeclampsia increases the risk of infant ROP, and this is seen when analysis is performed on the entire cohort of preterm and full-term infants. However, when assessing the direct effects of preeclampsia on ROP by restricting to preterm infants from the cohort, there is risk of selection and other biases since premature birth is an outcome of preeclampsia.
While these results show true differences in an association for ROP between the full-term and pre-term, low-birth-weight infants, these contradictory results may reflect biases in the current literature that restrict a cohort to prematurity, which is an outcome of preeclampsia.
While further research is needed, results from this study lend some clarity to the association between ROP and preeclampsia. Nonetheless, there is "biologic evidence that experimentally induced maternal uteroplacental insufficiency, in the absence of premature birth, may lead to mechanisms in offspring that protect against retinopathy," said Hartnett.
JAMA Ophthalmology. Doi:10.1001/jamaophthalmol.2017.2697
Published online August 10, 2017.