Final answer:
Without the exact figures for the maternal mortality rate in 2003 within the provided references, it is not possible to accurately fill in the blank for the maternal mortality rate in that year.
Step-by-step explanation:
The maternal mortality rate has seen a significant decrease from 1915 to 2003. Referring to the provided data, it can deduce that maternal mortality rates have declined worldwide due to improvements in healthcare, understanding of maternal health, and addressing disparities in access to care. However, the exact figure for the maternal mortality rate in 2003 is not provided within the provided references. Given the context and the pattern of decline in maternal mortality, the rates in developed countries have become quite low, but without the exact number in the references, we can't provide a confident answer to this specific year.