I start taking flomax since august 2011. my wife becomes pregnant on september. will it be harmful?

I'm sorry but I couldn't find any information about this as there doesn't appear to be any studies done on it's safety in pregnancy as Flomax is not approved for use in females, and unfortunately they haven't mentioned anything about what risks there are if the male partner is using it. This is what I could find:

Overview

It is not known if Tamsulosin can cause harm to the fetus. It is not known if Tamsulosin is found in breast milk. Tamsulosin is not approved for use in women.
Tamsulosin Pregnancy Warnings

Tamsulosin has been assigned to pregnancy category B by the FDA. Animal data have failed to reveal evidence of fetotoxicity, even after doses that yielded blood levels that were approximately 50 times the human therapeutic exposure. There are no approved indications for use of this drug in females.

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Animal data have revealed significantly reduced fertility in males after doses that yielded blood levels that were approximately 50 times the human exposure with the maximum therapeutic dose. The mechanism is believed to be an adverse effect on the vaginal plug formation possibly due to changes of semen content or impairment of ejaculation. The effects on fertility were reversible within three days after a single dose and four to nine weeks after multiple dosing. Multiple doses up to 16 times the human exposure did not significantly alter male fertility in animals. Human data are not available. Animal data have revealed significantly reduced fertility in females after doses that yielded blood levels that were approximately 50 times the human exposure with the maximum therapeutic dose. The mechanism is believed to be related to impairment of fertilization. Multiple doses up to 16 times the human exposure did not significantly alter female fertility in animals. Human data are not available. There are no indications for this drug in females.

http://www.drugs.com/pregnancy/tamsulosin.html