Monoamniotic twins

Source: Wikipedia, the free encyclopedia.
Various types of chorionicity and amniosity (how the baby's sac looks) in monozygotic (one egg/identical) twins as a result of when the blastocyst or embryo splits.

Monoamniotic twins are identical or semi-identical

fertilization.[3] Monoamniotic triplets or other monoamniotic multiples[4] are possible, but extremely rare.[1]
Other obscure possibilities include multiples sets where monoamniotic twins are part of a larger gestation such as triplets, quadruplets, or more.

Occurrence

Monoamniotic twins are rare, with an occurrence of 1 in 35,000 to 1 in 60,000 pregnancies.[1][5]

Complications

The survival rate for monoamniotic twins has been shown to be as high as 81% [6] to 95% [7] in 2009 with aggressive fetal monitoring, although previously reported as being between 50%[1] and 60%.[4] Causes of mortality and morbidity include:

  • Cord entanglement: The close proximity and absence of amniotic membrane separating the two umbilical cords makes it particularly easy for the twins to become entangled in each other's cords, hindering fetal movement and development.[4] Additionally, entanglement may cause one twin to become stuck in the birth canal during labor and expulsion.[1] Cord entanglement happens to some degree in almost every monoamniotic pregnancy.[1]
  • Cord compression: One twin may compress the other's umbilical cord, potentially stopping the flow of nutrients and blood and resulting in fetal death.[1][4]
  • Twin-to-twin transfusion syndrome (TTTS): One twin receives the majority of the nourishment, causing the other twin to become undernourished. TTTS is much more difficult to diagnose in monoamniotic twins than diamniotic ones, since the standard method otherwise is to compare the fluid in the sacs. Rather, TTTS diagnosis in monoamniotic twins relies on comparing the physical development of the twins.[1]

Diagnosis

gestational age of 15 weeks. There is no sign of any membrane between the fetuses. A coronal plane is shown of the twin at left, and a sagittal plane
of parts of the upper thorax and head is shown of the twin at right.

Ultrasound is the only way to detect monoamniotic-monochorionic twins before birth.[4] It can show the lack of a membrane between the twins after a couple of weeks' gestation, when the membrane would be visible if present.[4]

Further ultrasounds with high resolution

non-stress tests help to assess the situation and identify potential cord problems.[4]

There is a correlation between having a single

embryogenesis.[1]

Cord entanglement and compression generally progress slowly, allowing parents and medical caregivers to make decisions carefully.[4]

Treatment

Only a few treatments can give any improvements.

Sulindac has been used experimentally in some monoamniotic twins, lowering the amount of amniotic fluid and thereby inhibiting fetal movement. This is believed to lower the risk of cord entanglement and compression. However, the potential side effects of the drug have been insufficiently investigated.[1][4]

Regular and aggressive fetal monitoring is recommended for cases of monoamniotic twins to look for cord entanglement beginning after viability. Many women enter

perinatologist, an obstetrician that specialises in high-risk pregnancies.[4] However RCOG's guidelines[8] cite Dias et al.[9] in observing that cord entanglement is nearly always found in monoamniotic pregnancies and it is not clearly associated with poor outcomes, with most fetal deaths instead arising from twin reversed arterial perfusion
or fetal anomaly.

The clinical guidelines of

cesarean section between 32 and 34 weeks.[10][8] A retrospective study in 2016 argued that there is evidence vaginal delivery can be equally safe and reduce complications for some monoamniotic twins[11]
but this finding has not been incorporated into clinical guidelines.

See also

References

  1. ^ a b c d e f g h i j k l m n "Monoamniotic Twins". Pregnancy info.net. Retrieved July 9, 2009.
  2. ^ "Mono Mono Twins". Twin Pregnancy and Beyond.
  3. ISBN 0-8247-2844-0
    .
  4. ^ a b c d e f g h i j MoMo Twins; Monochorionic Monoamniotic Twins Archived 2016-04-08 at the Wayback Machine By Pamela Prindle Fierro, About.com. Retrieved on July 9, 2009
  5. ^ "How rare are MoMo twins". MoMoTwins.org. Retrieved Feb 14, 2022.
  6. S2CID 10186845
    .
  7. S2CID 37447326
    .
  8. ^
    PMID 27862859
    .
  9. PMID 20069540
    .
  10. ^ American College of Obstetricians and Gynecologists (ACOG) (May 2014). "Multifetal gestations: twin, triplet, and higher-order multifetal pregnancies". ACOG practice bulletin, no. 144. {{cite journal}}: Cite journal requires |journal= (help)
  11. S2CID 25507744
    .
Retrieved from "https://en.wikipedia.org/w/index.php?title=Monoamniotic_twins&oldid=1216682704"