The only way to determine sex is by viewing the flowers - male flowers will have a different appearance than female flowers. I guess you could take your chances, but I'd avoid planting this aggressive and potentially invasive vine altoghether.

I sure hope you are referring to American bittersweet and not the invasive alien species!!
"The powerfully invasive oriental bittersweet vines kill other vegetation, engulfing and killing it. The germination of a bittersweet seed in the ground at the base of a tree seems harmless enough. Yet, it won't take long for the oriental bittersweet vine to make it to the tree's crown, a la Jack's beanstalk made famous in folklore. It can be difficult to imagine a vine killing a tree, but oriental bittersweet vines have slain many a giant. Capable of reaching 4 inches in diameter, oriental bittersweet vines wrap so tightly around their victims that the trees are strangled, in a process called girdling by arborists. Even when oriental bittersweet vines aren't strangling a plant, they envelop it in so much shadow that they rob the plant of the sunlight required for proper photosynthesis. Conservation New England reports that, in the case of smaller trees, uprooting can even occur, as the trees' root systems are unable to contend with the massive weight of entrenched vines. "
"Asiatic bittersweet is distinguished from American bittersweet by the fact that its fruit and flowers are located in clusters of three to seven in the axil of the leaves (between the leaf and the stem). American bittersweet's fruit and flowers are located at the branch tips only. It is very important for land managers, naturalists, and gardeners to distinguish between the native species and the invasive species in any control efforts."

Here is a link that might be useful: American vs. oriental bittersweet

I saw an American Bittersweet vine today that was fully 6 inches in diameter. Fortunately someone had taken a chainsaw to it.

The thing about Bittersweet is that you have to plant it in an area where all the trees are expendable.

I suppose Bittersweet does have a place in the environment. It is the only vine in New England that can strangle an entire forest. Perhaps I could plant it next to red maples I do not like and it would smother them.

I used to like seeing bittersweet in dried arrangements and always thought it would be neat to grow it. That was before I moved to New England where it is a terrible scourge and I can't get rid of it.

Jim