Getting sick when you’re pregnant is especially difficult, but women whose children are at risk for developing asthma should avoid antibiotics, according to a new study.

The study, published in the Annals of Allergy, Asthma and Immunology, the scientific publication of the American College of Allergy, Asthma and Immunology (ACAAI), followed 298 mother-child pairs through the child’s third year of life.

The study found that 22 percent of the 103 children born to mothers who took antibiotics during pregnancy were diagnosed with asthma by age 3. In contrast, only 11 percent of the children born to mothers who didn’t take antibiotics prenatally were similarly diagnosed.