Monoamniotic twins

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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 Placentation.svg
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 twins that share the same amniotic sac within their mother's uterus. [1] Monoamniotic twins are always monochorionic and are usually termed Monoamniotic-Monochorionic ("MoMo" or "Mono Mono") twins. [1] [2] They share the placenta, but have two separate umbilical cords. Monoamniotic twins develop when an embryo does not split until after formation of the amniotic sac, [1] at about 9–13 days after 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.

Contents

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:

Diagnosis

Abdominal ultrasonography of monoamniotic twins at a 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. Monoamniotic twins at 15 weeks.jpg
Abdominal ultrasonography of monoamniotic twins at a 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 doppler imaging and non-stress tests help to assess the situation and identify potential cord problems. [4]

There is a correlation between having a single yolk sac and having a single amniotic sac. [1] However, it is difficult to detect the number of yolk sacs, because the yolk sac disappears during 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 inpatient care, with continuous monitoring, [1] preferably in the care of a 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 ACOG and RCOG both recommend premature delivery by 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

Related Research Articles

<span class="mw-page-title-main">Amniocentesis</span> Sampling of amniotic fluid done mainly to detect fetal chromosomal abnormalities

Amniocentesis is a medical procedure used primarily in the prenatal diagnosis of genetic conditions. It has other uses such as in the assessment of infection and fetal lung maturity. Prenatal diagnostic testing, which includes amniocentesis, is necessary to conclusively diagnose the majority of genetic disorders, with amniocentesis being the gold-standard procedure after 15 weeks' gestation.

<span class="mw-page-title-main">Stillbirth</span> Death of a fetus before or during delivery, resulting in delivery of a dead baby

Stillbirth is typically defined as fetal death at or after 20 or 28 weeks of pregnancy, depending on the source. It results in a baby born without signs of life. A stillbirth can often result in the feeling of guilt or grief in the mother. The term is in contrast to miscarriage, which is an early pregnancy loss, and sudden infant death syndrome, where the baby dies a short time after being born alive.

<span class="mw-page-title-main">Umbilical cord</span> Conduit between embryo/fetus and the placenta

In placental mammals, the umbilical cord is a conduit between the developing embryo or fetus and the placenta. During prenatal development, the umbilical cord is physiologically and genetically part of the fetus and normally contains two arteries and one vein, buried within Wharton's jelly. The umbilical vein supplies the fetus with oxygenated, nutrient-rich blood from the placenta. Conversely, the fetal heart pumps low-oxygen, nutrient-depleted blood through the umbilical arteries back to the placenta.

<span class="mw-page-title-main">Chorion</span> Outermost fetal membrane around the embryo in amniotes

The chorion is the outermost fetal membrane around the embryo in mammals, birds and reptiles (amniotes). It develops from an outer fold on the surface of the yolk sac, which lies outside the zona pellucida, known as the vitelline membrane in other animals. In insects, it is developed by the follicle cells while the egg is in the ovary. Some mollusks also have chorions as part of their eggs. For example, fragile octopus eggs have only a chorion as their envelope.

<span class="mw-page-title-main">Selective reduction</span> Abortion of one or more (but not all) fetuses in a multiple pregnancy

Selective reduction is the practice of reducing the number of fetuses in a multiple pregnancy, such as quadruplets, to a twin or singleton pregnancy. The procedure is also called multifetal pregnancy reduction. The procedure is most commonly done to reduce the number of fetuses in a multiple pregnancy to a safe number, when the multiple pregnancy is the result of use of assisted reproductive technology; outcomes for both the mother and the babies are generally worse the higher the number of fetuses. The procedure is also used in multiple pregnancies when one of the fetuses has a serious and incurable disease, or in the case where one of the fetuses is outside the uterus, in which case it is called selective termination.

Fetal distress, also known as non-reassuring fetal status, is a condition during pregnancy or labor in which the fetus shows signs of inadequate oxygenation. Due to its imprecision, the term "fetal distress" has fallen out of use in American obstetrics. The term "non-reassuring fetal status" has largely replaced it. It is characterized by changes in fetal movement, growth, heart rate, and presence of meconium stained fluid.

Oligohydramnios is a medical condition in pregnancy characterized by a deficiency of amniotic fluid, the fluid that surrounds the fetus in the abdomen, in the amniotic sac. It is typically diagnosed by ultrasound when the amniotic fluid index (AFI) measures less than 5 cm or when the single deepest pocket (SDP) of amniotic fluid measures less than 2 cm. Amniotic fluid is necessary to allow for normal fetal movement, lung development, and cushioning from uterine compression. Low amniotic fluid can be attributed to a maternal, fetal, placental or idiopathic cause and can result in poor fetal outcomes including death. The prognosis of the fetus is dependent on the etiology, gestational age at diagnosis, and the severity of the oligohydramnios.

<span class="mw-page-title-main">Umbilical cord prolapse</span> Complication of pregnancy where the umbilical cord slips out of the uterus prior to birth

Umbilical cord prolapse is when the umbilical cord comes out of the uterus with or before the presenting part of the baby. The concern with cord prolapse is that pressure on the cord from the baby will compromise blood flow to the baby. It usually occurs during labor but can occur anytime after the rupture of membranes.

<span class="mw-page-title-main">Twin-to-twin transfusion syndrome</span> Medical condition

Twin-to-twin transfusion syndrome (TTTS), also known as feto-fetal transfusion syndrome (FFTS), twin oligohydramnios-polyhydramnios sequence (TOPS) and stuck twin syndrome, is a complication of monochorionic multiple pregnancies in which there is disproportionate blood supply between the fetuses. This leads to unequal levels of amniotic fluid between each fetus and usually leads to death of the undersupplied twin and, without treatment, usually death or a range of birth defects or disabilities for a surviving twin, such as underdeveloped, damaged or missing limbs, digits or organs, especially cerebral palsy.

Rupture of membranes (ROM) or amniorrhexis is a term used during pregnancy to describe a rupture of the amniotic sac. Normally, it occurs spontaneously at full term either during or at the beginning of labor. Rupture of the membranes is known colloquially as "breaking (one's) water," especially when induced rather than spontaneous, or as one's "water breaking". A premature rupture of membranes (PROM) is a rupture of the amnion that occurs at full term and prior to the onset of labor. In cases of PROM, options include expectant management without intervention, or interventions such as oxytocin or other methods of labor induction, and both are usually accompanied by close monitoring of maternal and fetal health. Preterm premature rupture of membranes (PPROM) is when water breaks both before the onset of labor and before the pregnancy's 37 week gestation. In the United States, more than 120,000 pregnancies per year are affected by a premature rupture of membranes, which is the cause of about one third of preterm deliveries.

<span class="mw-page-title-main">Prelabor rupture of membranes</span> Medical condition

Prelabor rupture of membranes (PROM), previously known as premature rupture of membranes, is breakage of the amniotic sac before the onset of labour. Women usually experience a painless gush or a steady leakage of fluid from the vagina. Complications in the baby may include premature birth, cord compression, and infection. Complications in the mother may include placental abruption and postpartum endometritis.

<span class="mw-page-title-main">Nuchal cord</span> Medical condition

A nuchal cord is when the umbilical cord becomes wrapped around the fetus's neck. Symptoms present in the baby shortly after birth from a prior nuchal cord may include duskiness of face, facial petechia, and bleeding in the whites of the eye. Complications can include meconium, respiratory distress, anemia, and stillbirth. Multiple wraps are associated with greater risk.

Postterm pregnancy is when a woman has not yet delivered her baby after 42 weeks of gestation, two weeks beyond the typical 40-week duration of pregnancy. Postmature births carry risks for both the mother and the baby, including fetal malnutrition, meconium aspiration syndrome, and stillbirths. After the 42nd week of gestation, the placenta, which supplies the baby with nutrients and oxygen from the mother, starts aging and will eventually fail. Postterm pregnancy is a reason to induce labor.

<span class="mw-page-title-main">Velamentous cord insertion</span> Velamentous placenta

Velamentous cord insertion is a complication of pregnancy where the umbilical cord is inserted in the fetal membranes. It is a major cause of antepartum hemorrhage that leads to loss of fetal blood and associated with high perinatal mortality. In normal pregnancies, the umbilical cord inserts into the middle of the placental mass and is completely encased by the amniotic sac. The vessels are hence normally protected by Wharton's jelly, which prevents rupture during pregnancy and labor. In velamentous cord insertion, the vessels of the umbilical cord are improperly inserted in the chorioamniotic membrane, and hence the vessels traverse between the amnion and the chorion towards the placenta. Without Wharton's jelly protecting the vessels, the exposed vessels are susceptible to compression and rupture.

<span class="mw-page-title-main">Twin reversed arterial perfusion</span> Rare complication of monochorionic twin pregnancies

Twin reversed arterial perfusion sequence, also called TRAP sequence, TRAPS, or acardiac twinning, is a rare complication of monochorionic twin pregnancies. It is a severe variant of twin-to-twin transfusion syndrome (TTTS). In addition to the twins' blood systems being connected instead of independent, one twin, called the acardiac twin, TRAP fetus or acardius, is severely malformed. The heart is missing or deformed, hence the name "acardiac", as are the upper structures of the body. The legs may be partially present or missing, and internal structures of the torso are often poorly formed. The other twin is usually normal in appearance. The normal twin, called the pump twin, drives blood through both fetuses. It is called "reversed arterial perfusion" because in the acardiac twin the blood flows in a reversed direction.

<span class="mw-page-title-main">Monochorionic twins</span> Identical twins that share the same placenta

Monochorionic twins are monozygotic (identical) twins that share the same placenta. If the placenta is shared by more than two twins, these are monochorionic multiples. Monochorionic twins occur in 0.3% of all pregnancies. Seventy-five percent of monozygotic twin pregnancies are monochorionic; the remaining 25% are dichorionic diamniotic. If the placenta divides, this takes place before the third day after fertilization.

The following outline is provided as an overview of and topical guide to obstetrics:

<span class="mw-page-title-main">Circumvallate placenta</span> Medical condition

Circumvallate placenta is a rare condition affecting about 1-2% of pregnancies, in which the amnion and chorion fetal membranes essentially "double back" on the fetal side around the edges of the placenta. After delivery, a circumvallate placenta has a thick ring of membranes on its fetal surface. Circumvallate placenta is a placental morphological abnormality associated with increased fetal morbidity and mortality due to the restricted availability of nutrients and oxygen to the developing fetus.

Amnioinfusion is a method in which isotonic fluid is instilled into the uterine cavity.

The anomaly scan, also sometimes called the anatomy scan, 20-week ultrasound, or level 2 ultrasound, evaluates anatomic structures of the fetus, placenta, and maternal pelvic organs. This scan is an important and common component of routine prenatal care. The function of the ultrasound is to measure the fetus so that growth abnormalities can be recognized quickly later in pregnancy, to assess for congenital malformations and multiple pregnancies, and to plan method of delivery.

References

  1. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 "Monoamniotic Twins". Pregnancy info.net. Retrieved July 9, 2009.
  2. "Mono Mono Twins". Twin Pregnancy and Beyond.
  3. Shulman LS, van Vugt JM (2006). Prenatal medicine . Washington, DC: Taylor & Francis. p. 447. ISBN   0-8247-2844-0.
  4. 1 2 3 4 5 6 7 8 9 10 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. Hack KE, Derks JB, Schaap AH, Lopriore E, Elias SG, Arabin B, Eggink AJ, Sollie KM, Mol BW, Duvekot HJ, Willekes C, Go AT, Koopman-Esseboom C, Vandenbussche FP, Visser GH (February 2009). "Perinatal outcome of monoamniotic twin pregnancies". Obstetrics and Gynecology. 113 (2 Pt 1): 353–60. doi:10.1097/AOG.0b013e318195bd57. PMID   19155906. S2CID   10186845.
  7. Baxi LV, Walsh CA (June 2010). "Monoamniotic twins in contemporary practice: a single-center study of perinatal outcomes". The Journal of Maternal-Fetal and Neonatal Medicine. 23 (6): 506–10. doi:10.3109/14767050903214590. PMID   19718582. S2CID   37447326.
  8. 1 2 Royal College of Obstetricians and Gynaecologists (16 November 2016). "Management of Monochorionic Twin Pregnancy". BJOG. 124 (1): e1–e45. doi: 10.1111/1471-0528.14188 . PMID   27862859.
  9. Dias, T; Mahsud-Dornan, S.; Bhide, A.; Papageorghiou, A. T.; Thilaganathan, B. (12 January 2010). "Cord entanglement and perinatal outcome in monoamniotic twin pregnancies". Ultrasound Obstet Gynecol. 35 (2): 201–204. doi: 10.1002/uog.7501 . 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. Khandelwal, Meena; Revanasiddappa, Vanitha B.; Moreno, Sindy C.; Simpkins, Gunda; Weiner, Stuart; Westover, Thomas (May 2016). "Monoamniotic Monochorionic Twins—Can They Be Delivered Safely Via Vaginal Route?". Obstetrics & Gynecology. 127 (Supplement 1): 3S. doi:10.1097/01.AOG.0000483625.92567.88. S2CID   25507744.