Final answer:
The greatest impact on reducing maternal and infant mortality rates is likely to be through improved healthcare access, especially for the impoverished and addressing factors like ethnicity, and the provision of quality postnatal care and education.
Step-by-step explanation:
The greatest impact on decreasing maternal mortality and infant mortality rates in the United States is likely to come from improving access to quality healthcare, especially for those from poorer socio-economic backgrounds. Poverty, the unique American healthcare system, and ethnicity are significant contributors to higher infant mortality rates in the US. Furthermore, the availability of quality postnatal care, addressing malnutrition, providing education, and ensuring sanitary living conditions are critical in reducing these rates. The use of modern technology, such as mobile phones and financial technology services for faster access to funds and healthcare, may also contribute to decreasing mortality rates, as evidenced by research suggesting that mobile money transfers can lead to quicker treatment and better chances of recovery for infants.