Following is a response from Senior DHS staff member, Tom Pullum:
The following Stata lines will merge the PR and IR files, with one record for each woman in the IR file. Hope this is what you are looking for.
* PR/IR merge for ZM71, Zambia 2018 DHS
* specify a workspace
cd e:\DHS\DHS_data\scratch
use "...ZMIR71FL.DTA", clear
gen cluster=v001
gen hh=v002
gen line=v003
sort cluster hh line
save ZMIRtemp.dta, replace
use "...ZMPR71FL.DTA", clear
keep if hv117==1
gen cluster=hv001
gen hh=hv002
gen line=hvidx
sort cluster hh line
merge cluster hh line using ZMIRtemp.dta
tab _merge
keep if _merge==3
drop _merge
* save this file with another name