The calculation of the under-five rates is vastly more complex. DHS uses a synthetic (or life table) approach. Deaths and risk are assessed within an interval of time, such as the five years before the survey, and within eight sub-intervals of age. The method is described in the Guide to DHS Statistics https:// www.dhsprogram.com/pubs/pdf/DHSG1/Guide_to_DHS_Statistics_29 Oct2012_DHSG1.pdf.

It happens that within the next couple of weeks I will be putting a Stata program onto the DHS website that calculates these rates. I'm afraid you will have to wait until then.