1. JAMA Ophthalmology Journal Club Slides: Association of Maternal Smoking and Birth Weight With Later RNFL Thickness
Ashina H, Li XQ, Olsen EM, Skovgaard AM, Larsen M, Munch IC. 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. JAMA Ophthalmol. Published online March 2, doi: /jamaophthalmol

2. Introduction Importance:
Fetal exposure to the toxic effects of maternal tobacco consumption is widely known to be associated with adverse birth consequences.
Both maternal smoking during pregnancy and low birth weight have been implicated in impaired development of the retina.
Objective:
To investigate the associations of maternal smoking during pregnancy and low birth weight with retinal nerve fiber layer (RNFL) thickness in preadolescent children.

3. Methods
The Copenhagen Child Cohort 2000 Eye Study is a prospective, population-based, birth cohort study that included all children (n = 6090) born in 2000 in Copenhagen, Denmark.
Maternal smoking data were collected through parental interviews during pregnancy. Birth weight, pregnancy, and medical history data were obtained from the Danish Medical Birth Registry.
As a follow-up, the study performed eye examinations on 1406 of these children from May 1, 2011, to October 31, 2012.
Peripapillary RNFL thickness was measured using optical coherence tomography at the 11-year or 12-year follow-up examination.

4. Results
Of the 1406 children in the study, 1323 (94.1%) were included in the analysis.
In 227 children whose mothers had smoked during pregnancy, the peripapillary RNFL was on average 5.7 µm (95% CI, μm; P < .001) thinner than in 1035 children whose mothers had not smoked.
There was no difference identified in RNFL thickness when comparing 27 children whose mothers ceased smoking during pregnancy with 1035 children whose mothers had not smoked.
In low-birth-weight children (<2500 g), the RNFL was on average 3.5 µm (95% CI, μm; P = .02) thinner than in normal-birth-weight children.

5. Results
Characteristics of the Study Population Correlated With Maternal Smoking Status During Pregnancy

6. RNFL Thickness and Associated Factors in Children Aged 11 or 12 Years
Results
RNFL Thickness and Associated Factors in Children Aged 11 or 12 Years

7. Comment
Both maternal smoking during pregnancy and low birth weight were independently associated with having a thinner peripapillary RNFL at age 11 or 12 years.
The lack of a demonstrable RNFL deficit in children whose mothers ceased smoking during pregnancy may be a spurious finding, but no evidence suggests that it can ever be too late to stop smoking during pregnancy.
It remains to be determined whether more tissue means a higher number of optic nerve fibers and better resistance to optic nerve diseases, such as glaucoma.

8. Comment
There may be residual, unresolved confounding from socioeconomic effects included in the association with smoking.
In addition, we did not have information on maternal alcohol consumption during pregnancy or exposure to tobacco smoke in the form of passive smoking.
Overall, our observations support previous findings that intrauterine and perinatal factor can have long-lasting effects on the retina and the optic nerve.
These results add evidence to existing recommendations to avoid smoking during pregnancy and support measures that promote maternal and fetal health.

9. Conflict of Interest Disclosures
Contact Information
If you have questions, please contact the corresponding author:
Håkan Ashina, Department of Ophthalmology, Rigshospitalet, DK-2600 Glostrup, Copenhagen, Denmark
Funding/Support
The study was funded by the Bagenkop-Nielsen Foundation.
Conflict of Interest Disclosures
All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest and none were reported.