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Pregnancy & Breastfeeding

• Does pregnancy increase the risk of becoming infected with West Nile virus?
• Can a pregnant woman pass West Nile virus to her unborn baby?
• Can West Nile virus be passed to a child through breast milk?
• Should women with symptoms of West Nile virus continue to breastfeed their children?
• What steps should pregnant and breastfeeding women take to reduce their risk of getting West Nile virus?
• Is it safe for pregnant and breastfeeding women to use insect repellents that contain DEET?

Does pregnancy increase the risk of becoming infected with West Nile virus?

No. Being pregnant does not increase a woman's risk of getting infected with West Nile virus. Pregnant women who have concerns about West Nile virus or any other health concern should speak with their doctor or health care provider.

Can a pregnant woman pass West Nile virus to her unborn baby?

Yes, this can happen, although there are only a few known cases. In one confirmed case in the United States a mother passed West Nile virus to her unborn baby and in that case, the child was born with serious medical problems. However, it is not known whether the problems were caused by West Nile or by other factors. Since the evidence shows it is possible to pass West Nile virus to an unborn child, pregnant women should take immediate steps to reduce their risk of mosquito bites. If they develop symptoms of West Nile virus infection, they should call their doctor or health care provider right away.

Can West Nile virus be passed to a child through breast milk?

There is evidence that this is possible. In one case in the United States, a woman was infected with West Nile virus after the birth of her child. She breastfed her baby, and the baby later tested positive for West Nile virus infection. Laboratory tests determined that West Nile virus was present in the breast milk. Investigators looking into the case believe it is unlikely that the baby was infected by a mosquito bite. They concluded that breast milk was the most likely source of infection. Despite being infected with West Nile virus, the child had no symptoms and remained healthy.

Should women with symptoms of West Nile virus continue to breastfeed their children?

Women who are breastfeeding their children should contact their doctors for advice if they have symptoms of any illness, including West Nile virus. It appears that West Nile virus can be passed through breast milk, but the level of risk is still unknown. On the other hand, the health benefits of breastfeeding are well known. Women who have concerns about the potential to transmit West Nile virus through breastfeeding should consult their doctor for advice in their specific situation.

What steps should pregnant and breastfeeding women take to reduce their risk of getting West Nile virus?

Since there is evidence that West Nile virus could be passed through breast milk and from a mother to her unborn child, it is important for pregnant and breastfeeding women to take steps to reduce their risk of West Nile virus infection.

The best way to reduce the risk of infection is to reduce the risk of mosquito bites. You can do this in two ways:

1. Minimize your exposure to mosquitoes; and
2. Eliminate mosquito breeding sites around your home and vacation property.

By taking simple precautions to lessen your chance of being bitten by a mosquito, you can also lessen your chance of getting West Nile virus:

• When going outdoors, use insect repellents that contain DEET or other approved ingredients.
• Try to avoid spending time outdoors when mosquitoes are most active.
• Wear protective clothing such as long-sleeved shirts, long pants and a hat. Light coloured clothing is best because mosquitoes tend to be more attracted to dark colours.
• Make sure that door and window screens fit tightly and have no holes that may allow mosquitoes indoors.

To eliminate mosquito breeding sites around your home and vacation property:

• Regularly (twice a week) drain standing water from items like pool covers, saucers under flower pots, recycle bins, garbage cans, etc. It takes only four days for eggs to grow into adult flying mosquitoes.
• Remove old unused items from around your property (i.e., old tires) which have a tendency to collect water.
• Change the water in wading pools, bird baths, pet bowls and livestock watering tanks twice a week.
• Cover rain barrels with screens.
• Clean out eavestroughs regularly to prevent clogs that can trap water.
• Purchase an aerator or ornamental pond. This will keep the surface water moving which will make the water inhospitable to mosquito larvae.

Is it safe for pregnant and breastfeeding women to use insect repellents that contain DEET?

There is no evidence that the use of DEET by pregnant or breast-feeding women poses a health hazard to unborn babies or children who are nursing. However pregnant or breastfeeding women may wish to consider the use of non-chemical methods to prevent mosquito bites as a first line of defence against West Nile virus.

For more information on insect repellents, including a list of non-chemical ingredients, and reducing mosquito populations, visit the Pest Management Regulatory Agency Web site and click on Mosquito Control, or call 1-800-267-6315 (toll-free in Canada).