Doctors have known for quite some time that smoking while pregnant leads to an increased risk of giving birth to an underweight child. Now, a new study shows how smoking during pregnancy puts babies at risk of being born with a higher risk for eye diseases like glaucoma.
This new Danish study recorded the births of pregnant women, some of whom were smokers and some of whom were not. 80 percent of the women in this study didn't smoke during their pregnancy, whereas 18 percent were smokers and continued to smoke during pregnancy. 2 percent of women didn't smoke during pregnancy, however they did smoke beforehand.
After the babies were born, researchers measured every child's retinal nerve fiber. They found that all of the babies had an average retinal nerve fiber of 104 micrometers.
For those who don't know, retinal nerve fiber refers to a layer of fibers on the optic nerve that transmit visual signals from the retina to the brain. People with thinner than average retinal fiber layers have a higher susceptibility to diseases like glaucoma.
When researchers took a closer look at these babies, they found that the children born to those who smoked during pregnancy had retinal nerve fibers 5.7 micrometers thinner than children born to mothers who never smoked. Perhaps unsurprisingly, children of the women who stopped smoking during pregnancy also had stronger retinal fibers than the babies from mothers who smoked.
Researchers also noted that 4 percent of the babies in this study were born underweight. Since this study wasn't looking at the correlation between weight and retinal nerve fiber levels, there is no data do suggest being born underweight has any relation to the retinal nerve fiber levels in the eyes.
One critique leveled against this study is that there's no information on the socioeconomic status of the women involved in the research. This research also didn't show whether or not any of the mothers in the study were using alcohol during their pregnancy. Alcohol is well known to negatively impact fetal development.
Additionally, researchers don't have any data for how often or how many cigarettes the smoking mothers used each day. There's also no data on what kinds of tobacco products these women used.
Christopher Kai-Shun Leung, who works as a researcher at the Chinese University of Hong Kong, wrote an editorial piece about this study. Dr. Leung said this study reveals how smoking for even a short time period during pregnancy could have devastating effects on the baby's eye health.
Although Dr. Leung believes there's real value in this study, he believes more studies need to be done on this topic to understand the direct link between smoking and retinal nerve fiber levels. One issue Dr. Leung had with the study is the fact that the differences between retinal nerve fiber layers of smokers and non-smokers wasn't large enough to signal serious eye issues.
Despite his critique, Dr. Leung says that every mother who smokes during pregnancy should take these findings seriously. Even a small decrease in the thickness of retinal nerve fiber could have long-term effects on a child's vision.
Hakan Ashina, who works at the Rigshospitalet in Copenhagen, was the lead author on the study. This study, which was published under the name "Association of Maternal Smoking During Pregnancy and Birth Weight With Retinal Nerve Fiber Layer Thickness in Children Aged 11 or 12 Years The Copenhagen Child Cohort 2000 Eye Study," can be found in the latest edition of JAMA Ophthalmology.