Derivation
variable: dmisabest [decade estimate of most recent (since last birth) miscarriage/abortion] (table[s]: tb_tbxto2007, tbold_part1/2, tb_tboto2007, tbold_control)
variable: dmisabmm [most recent (since last birth) miscarriage/abortion month] (table[s]: tb_tbxto2007, tbold_part1/2, tb_tboto2007, tbold_control)
variable: dmisabyear [most recent (since last birth) miscarriage/abortion year] (table[s]: tb_tbxto2007, tbold_part1/2, tb_tboto2007, tbold_control)
gen recbirdatex=2 if recbiryear~=.
replace recbirdatex=4 if recbirmm==. & recbiryear~=.
replace recbirdatex=5 if recbirest~=. & recbiryear~=.
la val recbirdatex datex