In partnership with Changamka MicroHealth Ltd., and with the support of Grand Challenges Canada, we evaluate the impact of mobile phone-based vouchers for maternal care delivered to poor women in Vihiga District, near Lake Victoria in Western Kenya. We aim to increase the timely use of ante-natal care services, and to at least double the share of attended deliveries from a base of about 26%. We target 1,500 women to take part in the randomized control trial, providing some with vouchers for ante-natal care, delivery, and post-natal care, some with transport vouchers, and some with both.