# Locked twins

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'''Locked twins''' is a rare complication of [multiple pregnancy](/source/multiple_pregnancy) where two fetuses become interlocked during [presentation](/source/Presentation_(obstetrics)) before birth. It occurs in roughly 1 in 1,000 twin deliveries and 1 in 90,000 deliveries overall.<ref name=borah>{{cite journal|title=Locked Twins: A Rarity|journal=Annals of Medical and Health Sciences Research|first1=T.|last1=Borah|first2=A.|last2=Das|year=2012|pages=204–205|issue=2|volume=2|doi=10.4103/2141-9248.105676|pmid=23439954|pmc=3573520 |doi-access=free }}</ref> Most often, locked twins are delivered via [Caesarean section](/source/Caesarean_section), given that the condition has been diagnosed early enough. The fetal mortality rate is high for the twin that presents first, with over 50% being [stillborn](/source/stillborn).

==Description==
There are two types of locked twins: breech/vertex and vertex/vertex. In breech/vertex presentations, which are much more common, the first twin is in the [breech position](/source/breech_position), presenting feet-first, and the second is in the [cephalic](/source/Cephalic_presentation) (vertex) position, presenting in the normal head-first manner.<ref name=jacob>{{cite book|title=A Comprehensive Textbook of Midwifery and Gynecological Nursing|page=343|last=Jacob|first=Annamma|publisher=[Jaypee Brothers](/source/Jaypee_Brothers)|year=2012|isbn=9789350255575}}</ref> In these cases, the chin of the first twin locks behind the chin of the second twin while in the [uterus](/source/uterus) or [birth canal](/source/birth_canal), preventing [vaginal delivery](/source/vaginal_delivery).<ref name=fortner>{{cite book|title=The Johns Hopkins Manual of Gynecology and Obstetrics|page=119|editor-last=Fortner|editor-first=Kimberly B.|publisher=[Lippincott Williams & Wilkins](/source/Lippincott_Williams_%26_Wilkins)|year=2007|isbn=9780781762496}}</ref> In vertex/vertex presentations, where both twins are positioned for head-first delivery, the two heads become locked at the [pelvic brim](/source/pelvic_brim), preventing either fetus from passing through the [pelvic inlet](/source/pelvic_inlet) in a vaginal delivery.<ref name=jacob/>

Contributing factors to the interlocking of twins include uterine [hypertonicity](/source/hypertonicity), small fetal size, and reduced levels of [amniotic fluid](/source/amniotic_fluid) following [rupture of the membranes](/source/rupture_of_the_membranes).<ref name=fortner/> It is more likely to occur in women with large pelvises, young [primigravida](/source/primigravida)e (young women in their first pregnancy), and pregnancies with [monoamniotic twins](/source/monoamniotic_twins).<ref name=borah/>

==Management==
If locked twins are diagnosed in early delivery, before either twin is born, both fetuses can be delivered by [Caesarean section](/source/Caesarean_section). If one fetus has been partially born, attempts can be made to disimpact the twins manually, such as by the [Zavanelli maneuver](/source/Zavanelli_maneuver), with a view to performing an assisted delivery with [ventouse](/source/ventouse) or [forceps](/source/Forceps_in_childbirth).<ref name=kock>{{cite book|title=Maternal and Newborn Care: A Complete Guide for Midwives and Other Health Professionals|page=25.5|publisher=Juta Academic|last1=De Kock|first1=Joanita|last2=Van der Walt|first2=Christa |year=2004|isbn=9780702164026}}</ref> If the diagnosis is made only after the first locked twin has died in the birth canal, or if it is not expected to survive, the first twin may be [decapitated](/source/Decapitation) and its head pushed up to allow safe delivery of the second twin.<ref name=jacob/><ref name=kock/>

At least one case has been reported where [hexoprenaline](/source/hexoprenaline) was used to relax the uterine [smooth muscle](/source/smooth_muscle) to thereby temporarily inhibit labour and disimpact the fetal heads.<ref name=borah/>

==Outcomes==
Since locked twins are often diagnosed in the late stages of delivery, it is often too late to intervene to save the life of the first twin and thus there is a high rate of [stillbirth](/source/stillbirth), estimated to be over 50%.<ref name=borah/><ref>{{cite book|title=Selected Topics in Obstetrics and Gynaecology-2|page=65|year=2006|first1=Shirish N. |last1=Daftary |first2=Shyam V. |last2=Desai|publisher=BI Publications|isbn=9788172252328}}</ref>

==References==
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== External links ==
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{{Pathology of pregnancy, childbirth and the puerperium |state=expanded}}

Category:Complications of labour and delivery
Category:Twin
Category:Stillbirth

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Adapted from the Wikipedia article [Locked twins](https://en.wikipedia.org/wiki/Locked_twins) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Locked_twins?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.