The Switch Rhinocort Aqua, a nasal steroid used to treat nasal allergy symptoms, has been found appropriate for use by pregnant women. On the basis of data submitted by the drug's maker, AstraZeneca, the Food and Drug Administration upgraded the prescription drug last month from a pregnancy safety rating of category C (no birth defects data available) to category B (no increased risk of birth defects shown). The change in status makes the drug the first nasal steroid approved for pregnant women; this kind of drug is generally regarded as safer in pregnancy than a systemic allergy drug (like Zyrtec, Claritin and Benadryl , all of which have B ratings).

The Evidence Data submitted by AstraZeneca showed that birth defects were no more common among nearly 3,000 Swedish women who used the drug during pregnancy and gave birth between 1995 and 1998 than among some 290,000 other Swedish women who gave birth in that same period.

The Caution Despite the new rating, allergists advise pregnant women to check with their doctor before using the drug. The rule in pregnancy is to limit use of drugs, even those with good study data, says Beth Corn, head of the allergy clinic at the Mount Sinai Medical Center in New York. A safer first option for a pregnant woman, said Corn, would be saline spray or drops -- basically salt water -- to flush out nasal passages.

The Alternatives Category C nasal steroids such as Flonase and Nasonex, which are sometimes prescribed for pregnant women, may be just as safe as Rhinocort, but there is little research to prove it, say obstetricians. The makers of these products say they have no plans to study the drugs' safety in pregnant women.

-- Francesca Lunzer Kritz