What is Vanishing Twin?
Vanishing twin is a phenomenon, in which early ultrasonography scan conducted within six to ten weeks result reported a twin pregnancy, but only one baby seen in the scan conducted less than 12 weeks after conception. It has been observed bleeding and loss of tissue are symptoms of typical miscarriage, but vanishing twin syndrome is asymptomatic.
In vanishing twin syndrome, the growth of the embryo merely ended at very early stage and reabsorbed within the gestational sac or can produce compressed fetus or cause subtle abnormality on the placenta, which includes the formation of a cyst, fibrin or shapeless materials1,2,5.
Causes of Vanishing Twin
Anomalies that effect in the vanishing of a fetus usually happen at the early stage of fetus development rather than happening from a sudden slur. Placental or fetal analysis often discloses the involvement of abnormal chromosomal fact.
These abnormalities include the existence of diploidy, triploidy, and sex chromosome variation and consequences on pathological findings in placenta, repeated villus sampling and skin biopsies. Therefore, researchers assume that the vanishing twin syndrome has a chromosomal abnormality follows disappearance.
It also assumed that inappropriate cord implantation has a role in vanishing twin syndrome1,2,6.
Vanishing Twin Predominance
Globally the rate of multiple gestations is almost 3.3 percent to 5.4 percent at eight weeks of pregnancy. Whereas, vanishing twin syndrome occurs in 21 percent to 31 percent of multiple gestations. Furthermore, research data showed that 10 percent to 15 percent of single birth is resultant of twin gestation2.
Vanishing Twin Syndrome Symptoms
Vanishing twin usually appears within the first trimester and does not provide typical symptoms as in normal miscarriage. But some females reported that they experience mild bleeding and cramping. In rare cases, vanishing twin syndrome can appear at second and third trimester with mild bleeding and cramping2,3,6.
Survivors & Complications
Usually mother has less life risk, but usually face some maternal complications like premature delivery, infection of retained fetus, severe bleeding after delivery, heavy clotted bleeding, obstructive labor needs cesarean delivery.
But some complications occur in a live fetus. The possible morbidity is cerebral palsy, poor perfusion through vascular linkage by placental anastomoses, short-term hypotension, and skin necrosis. Medical attention requires to monitor and management of these conditions, otherwise, the life of the fetus become in danger.
Other complications include the low birth weight of the remaining fetus. This also has serious medical consequences like restricted intrauterine growth, which increase the risk of mortality and may require hospitalization and admission to neonatal care unit.
- Premature delivery may occur before 37 weeks of gestation, but in vanishing twin syndrome influence very premature delivery before 32 weeks of gestation, which increases the risk of mortality almost three-fold more than full term delivery.
- Cerebral palsy may resultant of transmission of thromboplastin protein from the departed fetus to the remaining fetus and this leads to increase the load of thromboplastin. Excessive load of thromboplastin can damage central nervous system of the survive fetus.
- Decreased vascular perfusion may the primary reason of development of cutis aplasia2,4.
Factors Affecting Vanishing Twin
Vanishing twin syndrome is not gender bias disorder, both sexes of the fetus have similar tendency to develop this abnormality. There is no report found in favor of race-specific incidence. But researchers suspected that advanced maternal age has increased the risk of placental and fetal chromosomal abnormalities. Usually, older than 30 years of females have a higher tendency to develop vanish twin syndrome2.
Some important considerations require for precautionary purpose, these are
- Definite confirmation about no viable fetus residue present is required before performing dilation and curettage.
- In repeated performance of villus sampling for a multifetal gestation may cause the presence of mosaic placenta.
- There is a risk of vanished twin with abnormal chromosomal placenta may interfere a viable fetus with normal chromosomes. However, implantation of multiple eggs with reabsorption of several during the course of the pregnancy multiple eggs in fertility treatments is yet now unclear.
- Parents have to more careful about their singleton children because vanishing twin syndrome can affect survive fetus and provides many complications. Research study findings found that after preterm birth of the child with vanishing twin syndrome has a tendency to get motor difficulties.
- If parents already had vanishing twin syndrome, then they should aware about threatened abortion.
Some misguiding diagnostic features may be considered as vanishing twin syndrome, which include
- Decidual response on ultrasonography
- Observing of amniotic cavity through sonogram and considered as a second fetus
- Examine the chorionic sac through sonogram and considered as a second fetus
- Observation of yolk sac or extraembryonic coelom through sonogram and considered as a second fetus
- Observing of hydropic transformation in chorionic villi or subchorionic hemorrhage through sonogram and considered as a second fetus2,4,6.
Following are the tests perform in the gynae and obstetrics unit in hospital or clinic
Different biomarkers like plasma protein-A, Alpha-fetoprotein, Beta-human chorionic gonadotropin are tested in the laboratory for vanishing twin syndrome. But the biomarkers reports are only provided correct result in vanishing twin syndrome, but if a dead fetus remains in the sac, then obtained result is faulty.
Amniocentesis can also perform in the laboratory, but there is a chance of false-positive results in a vanishing twin fetus.
Ultrasonography provides confirmation for vanishing twin syndrome2.
Treatment and Management
No special treatment require for uncomplicated vanishing twin syndrome. But due to the risk of several complications the clinician must provide special attention to avoid infection and consumptive coagulopathy by periodic careful monitoring of the survive fetal growth. In addition, instruct pregnant women if vaginal hemorrhage, cramping, and/or pelvic pain occur then immediately ask for medical care. Dilatation and curette usually requires after confirmation of no viable remains through imaging diagnosis2,6.
- What is vanishing twin syndrome? Online available at http://www.babycentre.co.uk/x563309/what-is-vanishing-twin-syndrome
- Ann L Anderson-Berry; Vanishing Twin Syndrome; Online available at http://emedicine.medscape.com/article/271818-overview#a6
- Vanishing Twin Syndrome; American Pregnancy Association; Online available at http://americanpregnancy.org/multiples/vanishing-twin-syndrome/
- Evonne Lack; Strange but true: Vanishing twins; Online available at http://www.babycenter.com/0_strange-but-true-vanishing-twins_10364948.bc
- Vanishing Twin Syndrome, Online available at http://www.babycenter.com/0_strange-but-true-vanishing-twins_10364948.bc
- Vanishing Twin Syndrome, Online available at https://www.huggies.com.au/childbirth/multiple-births/twins/vanishing-twin-syndrome