This issue is not clearly delineated from the research available. I haven't heard of any research done by Biogen on women taking Avonex who find out they are pregnant. I'm about to get married and plan to have a family someday. I figure that since I'll be on Avonex for quite some time, the chances I'll get pregnant on it could be pretty high. I read about one woman who was 23 months in February of last year who found she was pregnant while on Avonex and immediately stopped using the drug.
Information concerning the concomitant use of beta interferons and pregnancy is scant at best.
Not enough numbers are available for a firm answer in this area. The recommendation is that for any woman on beta interferons, such as Avonex, that a period preceding conception of two months be without the presence of drugs. Certainly, if conception is achieved, than Avonex or other beta interferons should be avoided during pregnancy. The medication can be resumed following pregnancy. At present there is no firm data that there is a risk but, to be on the safe side, it is recommended that these treatments be avoided during conception and pregnancy.