A million times each year in the U.S. a pregnant woman who is not remotely ready for delivery thinks she's entering preterm labor. Chagrin Falls-based CerviLenz wants her to know for sure -- at less cost. The best way until now to determine if the expecting mother is in fact in labor is to take an accurate measurement of cervical length. That requires an expensive transvaginal ultrasound. CerviLenz is marketing an inexpensive, easy-to-use disposable device that can quickly and accurately tell if a woman is about to give birth. Invented by a practicing obstetrician, the device is the first and only of its kind. The company is adding staffers in the field and will soon reach 12 employees. The devices are manufactured in Ohio.