By week seven, the embryo is already squirming about. But at this point it's so small you can't possibly feel its periodic contortions. In fact, it may be several more months before the fetus makes his presence known to you. The usual time frame is more like 18 to 22 weeks, though, especially for first pregnancies. Veteran moms tend to feel fetal movement earlier than first-time moms.
Uterine muscles are less taut, so a woman is more sensitive to soft kicking.
Besides, if you've been pregnant before, you'll probably recognize the feel of a fetal kick, and can differentiate it from other belly rumblings, such as say, gas. Bear in mind, too, that your build may have something to do with when you'll be able to distinguish a hunger pang from a left jab. Women with smaller frames tend to feel movement earlier than women who are overweight. That said, we'll give it a try. Typically, you might first recognize a delicate tapping.