Maternal Smoking During Pregnancy Weakens the Child’s Optic Nerve – University of Copenhagen

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07 March 2017

Maternal Smoking During Pregnancy Weakens the Child’s Optic Nerve


New research from Rigshospitalet, Zealand University Hospital and the University of Copenhagen shows that the link between the retina and the brain is weaker in children whose mother smoked during pregnancy.

Danish researchers have just completed the first large study of the optic nerve in children. It shows that the optic nerve of children aged 11-12 years is thinner among children whose mother smoked during pregnancy than among children whose mother did not smoke. The study has just been published in the esteemed journal JAMA Ophthalmology. A total of 1,323 Danish children participated in the study.

‘We discovered a five-per cent deficiency in the optic nerve tissue when we compared children of mothers who smoked during pregnancy to children of mothers who did not smoke. This difference was not affected by other differences between the children, such as birth weight’, says Student of Medicine Håkan Ashina, who conducted the study as part of his bachelor project and is the first author of the article.

The researchers are not familiar with the biological mechanism behind cigarette smoking’s effect on the optic nerve. However, they do know that the number of nerve fibres is higher at the early stages of pregnancy, and that around half of the nerve fibres are normally discarded later in the pregnancy as part of the natural maturation of the optic nerve.

‘It may be this process that is affected by the substances consumed through cigarette smoking’, says Professor Michael Larsen from the Department of Clinical Medicine at Rigshospitalet, who supervised the project.

Weak Link May Affect Eyesight
A thin optic nerve does not determine whether or not the child needs glasses, but it may affect the child in the long term, says Research Associate Professor Inger Christine Munch from the Department of Ophthalmology at Zealand University Hospital, who is the senior author of the article: 

’The optic nerve loses nerve fibres throughout life, and if the number of nerve fibres drops below a certain level the person will develop glaucoma with blind spots in the field of vision. We can therefore assume that people are better equipped to avoid developing glaucoma and blindness if they are born with a more well-developed optic nerve’.

The Eye Is Part of the Central Nervous System
The optic nerve, which is the link between the eye and the brain, is part of the central nervous system.

‘We still do not know whether smoking during pregnancy affects the brain or the optic nerve specifically. In other contexts, the optic nerve is highly sensitive to innate weaknesses in energy metabolism and to drugs that weaken energy metabolism, e.g. tuberculosis medicine. We also have the data to study such connections, and we are doing so in ongoing research projects’, Michael Larsen says.