Sudafed while breastfeeding?

I wouldn't. The american academy of pediatrics says that sudafed is compatible with breast feeding. However, it's known to enter the milk; I advise against using any medicine that enters the milk unless you really have to, and I don't know of any situation where you really have to use sudafed.
Safe. But you always want to minimize baby's exposure to drugs. Take cautiously as needed.

Related Questions

I'm breastfeeding & dr rxd sudafed & guifen w/ codeine. Haven't taken yet but baby is sick now so will medicine passed into milk help him feel better?

No. Only tiny amounts of a breastfeeding mom's cold & cough meds get into her breastmilk, so should not affect the baby. Older babies with mild cold symptoms (such as stuffy/runny nose and mild cough, but are still happy/active) can be watched at home if ok with the doctor. The baby's doctor may want to test the baby for strep throat or the flu. Young babies under 3 months should be seen by a doctor.
Careful. Be careful taking sudafed while breastfeeding. It can decrease your milk supply. Codeine might make you sleep more soundly and not wake to your crying baby, or fall asleep while breastfeeding, which can be very dangerous (dropping baby to floor or rolling on baby/suffocating him). Add water to the air (humidifier) and flush your nose with saline. Honey can help coughs (for those over 1 yr old).
No. The Codeine will pass into breastmilk but its use is highly discouraged as some mothers are 'rapid metabolizers" of Codeine and can concentrate codeine's final product, morphine, in the milk. Pseudophedrine can decrease your milk supply. The best way to make your baby feel better is to breastfeed. The antibodies you are making to your cold are passing through your milk and are great protection.