My wife has cervical length 3cm at 21 week  in anamoly scan and was 3.9 cm at 17 week scan . During previous pregnancy we had abortion due no absent of cardic  activity in fetus at 5th month through normal delivery .this time  in anamoly scan placenta is right lateral posterior low lying , lower edge covering the internal os n doctor suggested we need cervical stitch ( cervical carclage) what should we do now , is it necessary to do this ? N what are the major risk of cervical carclage