Light duty

Hi, i just went for my 1st appt yday. Requested for light duty letter for me to submit to my employer, but doc says i just need to work it out with my employer. (My jobscope involves lots of walking/standing and a bit of running when there's a need to. But there's also counter based work that all my pregnant colleagues went through during their pregnancy.) Problem is, my company need a black and white letter for them to approve the light duty and accomodate to my pregnancy. Hv any moms ever managed to get doc to write one?