Hello, While Diphenhydramine has not been assigned a specific category by the FDA, studies have revealed that birth defects may, indeed, be associated with its use, though there is no definite evidence. So, instead of using this medication, I would suggest going for natural remedies to attain relief. Yet, if her consultant feels it necessary she may take it. Other remedies include steam inhalations using nilgiri oil, turmeric and vicks, using saline gargles and warm water to drink, local application of Vicks vaporub etc. Hope this helps.