A total of 212 pregnant women ( 24 to 36weeks ' gestation ) , aged at least 17years , with LBPGP , will be randomly assigned to the verum auricular acupuncture plus standard obstetric care group ( VAAc ) , to the non-specific auricular acupuncture plus standard obstetric care group ( NSAAc ) , to the non-specific placebo auricular acupuncture plus standard obstetric care group ( PAAc ) , or the standard obstetric care group ( SOC ) .