Question: [Yebamoth 61b](http://halakhah.com/yebamoth/yebamoth_61.html#PARTb) discusses the positive commandment of being fruitful and multiplying. As far as I am aware, one makes no blessing before intercourse. Why not?

Please cite sources!

Answer: 
The Maggid Ta'alumos to the Rif on Maseches Berachos, daf 35a (25a in pages of the Rif) says that we do not make the blessing because she may not get pregnant and then the mitzvah was not fulfilled. He also addresses that Onah is a negative commandment and therefore has no blessing.

However, he does indicate that the blessings under the Chuppah do constitute a general birkas hamitzvah.
UPDATE FOUND THIS:

> 
> The גליוני הש"ס to Berachos 35a discusses that there should be a
>  blessing on marital relations, and concludes that Birkas Ha'erusin
>  accomplishes that. It would seem he held this concept can extend to
>  other pleasures, although this could still be in the realm of "a need
>  of the body.
>  <https://judaism.stackexchange.com/a/34856/1857>
> 
> 
>