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interlocking
/in·ter·lock·ing/ (-lok´ing) closely joined, as by hooks or dovetails; locking into one another.A rare—circa 1:1,000 twin gestations—complication of vaginal delivery of twins; the 1st twin presents in breech and descends ‘locking’ his/her head above the head of the 2nd twin in vertex presentation; if the 2nd baby is already in the pelvis, loss of 1st baby is almost inevitable and interventional decapitation of 1st infant may be necessary to save the 2nd infantinterlocking
Obstetrics A rare complication of vaginal delivery of twins; the 1st twin presents in breech and descends 'locking' his head above the head of the 2nd twin in vertex presentation; if 2nd baby is already in the pelvis, loss of 1st baby is almost inevitable and interventional decapitation of 1st infant may be necessary to salvage the 2nd infant Prevention C-section. Cf Selective termination.