Vanishing Twin Syndrome And Its Connection To Maternal Health

When you hear the sentence “a vanishing twin”, you think to yourself, is it possible for a baby to vanish or disappear just like that? Does this baby really vanish, as if this were happening in a movie? And if this does occur, where does this baby go, and what about the other twin? Actually, sometimes one of the twins does vanish inside the uterine and the other one usually stays alive, and this is called vanishing twin syndrome.

What is vanishing twin syndrome?

• As you can deduce from the name, vanishing twin syndrome (VTS) means one of a set of twins or multiple embryos dies in the uterus, disappears, or gets resorbed partially or entirely, leading to a singleton pregnancy¹
• The loss of the twin could happen like a regular miscarriage, and in this case, the pregnant parent is often aware of the condition, or it could occur in the form of vaginal bleeding or spotting, which is a common complication during the first trimester, and in this case, the twin loss usually goes unnoticed¹
• It has been estimated that vanishing twin syndrome occurs in about 50% of pregnancies that start with three or more gestational sacs, in about 36% of twin pregnancies, and in about 12-30% of in-vitro fertilisation pregnancies²

Causes of vanishing twin syndrome

There are several factors that were found to contribute to the vanishing twin syndrome:¹

• Advanced maternal age (> 30 years)
• Chromosomal abnormalities in the lost twin
• The utilisation of assisted reproductive techniques (ART), such as in vitro fertilisation (IVF)
• Genetic and teratogenic factors
• Anatomical abnormalities in the placenta, such as a small placenta
• Increase the incidence of multiple gestations

How does vanishing twin syndrome occur?

Vanishing twin syndrome may occur through one of these three possible mechanisms:

The resorption of the vanishing twin

It’s still unknown how exactly the process of resorption occurs, yet it is the most likely physiologic explanation for VTS. Resorption often happens in the first trimester, and the evidence suggests that it doesn’t affect the surviving twin. Some study results have shown that it can be observed from the seventh week to the twelfth week of gestation.¹

Blighted ovum

A blighted ovum means that there is no embryo inside the gestational sac that can be seen via ultrasonography. Some studies found that most vanishing twin cases were found to be anembryonic pregnancies that existed alongside normal pregnancies. This case could result in vaginal bleeding in the first trimester, which means that the anembryonic sac has been expulsed. In this situation, it’s recommended to make a thorough ultrasonographic examination before doing any dilation or curettage (removal of tissue from inside of the uterus) as this may lead to the accidental abortion of the other live twin.¹

Foetus papyraceous

Foetus papyraceous is a very rare condition, mostly occurring in multiple gestations. It means that the vanishing foetus is compressed or flattened between the other viable foetus and the uterine wall. It usually happens at the beginning of the second trimester. The vanishing foetus might be completely resorbed, or it might be macerated (softened and separated) as the pregnancy continues and negatively affect the viable twin. This situation could be observed via regular ultrasonographic examinations.¹

Vanishing Twin Syndrome and its connection to maternal health

Many studies have been conducted to examine vanishing twin syndrome and its connection to maternal health. In one study, there was a comparison between vanished twin pregnant parents and other pregnant parents in regards to pregnancy and labour complications and outcomes. The results showed that vanished twin pregnant parents were more susceptible to the following pregnancy and labour complications: gestational diabetes mellitus, intrauterine growth restriction (IUGR), chronic hypertension (high blood pressure), hypertensive disorder, premature rupture of membranes (PROM), polyhydramnios, oligohydramnios, vasa previa, cervical insufficiency, second trimester bleeding, labour induction, and preterm delivery.³

In a group of studies, it was estimated that vanishing twin syndrome leads to various pregnancy complications, especially after IVF procedures. These outcomes include gestational and pregestational diabetes, preeclampsia, placenta previa, placental abruption, retained placenta, and operative delivery.⁴

Nevertheless, most of the cases only suffered from more minor complications including vaginal bleeding or spotting, pelvic pain, or uterine cramps. These usually occurred in the first trimester, and most of the pregnant parents don’t notice that they have gone through an abortion.¹

The effects of Vanishing Twin Syndrome on the surviving twin’s health

A study showed that the twin survivor of vanishing twin syndrome had an increased risk of negative perinatal outcomes. In the early stages of the condition, the surviving twin is at risk of low birth weight, newborn jaundice, and oligohydramnios in the exposed foetus. While in the late stages of the condition, the twin is at a higher risk of oligohydramnios, preterm birth, and neonatal intensive care unit admission. Moreover, maternal nulliparity (has never given birth) and ovulatory dysfunction were found to be associated with the incidence of an early vanished twin, which means that the pregnant parent probably had to undergo IVF, or intracytoplasmic sperm injection pregnancy.⁵

It was observed that the incidence of the vanished twin occurring in the second semester indicated a higher risk for the viable twin in terms of growth restriction, premature delivery, and perinatal mortality when compared to the first trimester.² The viable twin here might suffer from cerebral palsy and foetal malformations.¹

Diagnosis of Vanishing Twin Syndrome

It has been established that ultrasound examination during pregnancy can confirm the existence of the vanishing twin.¹

A study was conducted to compare the level of the hormone human chorionic gonadotropin (hCG) between normal twin pregnancies and vanishing twin pregnancies, and it was observed that pregnant parents with vanishing twin pregnancies have a slightly higher hCG level than the normal ones. It is suggested that the abnormal levels of this hormone may have existed in the earlier days of the implantation.¹

After giving birth, an examination of the placenta could help to establish further details about the vanishing twin.¹

It is critical to apply the ultrasound carefully, especially in the early stages of the pregnancy, because it could lead to incorrect interpretation, such as diagnosing a placental cyst incorrectly as a gestational sac.¹

Management of Vanishing Twin Syndrome

Where there aren’t any adverse effects or complications after losing the foetus, there is not any need for specialist medical care. However, when the vanished twin leads to severe outcomes, whether for the pregnant or the surviving twin, the pregnancy should be treated as a high-risk pregnancy in order to prevent any further complications.¹

It is also important to make regular prenatal visits to monitor the health of the pregnant parent and the surviving twin to detect any adverse signs as early as possible.¹

FAQ’s

How long do you bleed with vanishing twin syndrome?

It depends on the severity of the case; in simple cases, which represent the majority of cases, it is usually a similar amount to spotting, whereas in severe cases it could be more significant.

Does vanishing twin syndrome affect the surviving baby?

This also depends on the severity of the case. In simple cases, the surviving baby is not affected, whereas in severe cases, they may experience serious complications.

What are the psychological effects of vanishing twin syndrome?

It’s normal for a pregnant parent to go through grief after vanishing twin syndrome due to the distress of experiencing a miscarriage and losing their baby, yet they are still pregnant and should take care of themselves and the surviving baby. Therefore, it is crucial that the pregnant parent seeks help to support their health, not just physically but also mentally, for example by talking to a specialist and spending time with friends and family. They also should ask their healthcare provider for important information and details about their case in order to understand exactly what they are experiencing.

Summary

Vanishing twin syndrome is a condition in which one of the twins disappears from the uterus in different ways. Most of the time, it occurs without any obvious or severe symptoms; therefore, it might happen without the pregnant parent’s knowledge. However, in some cases, it may lead to numerous serious complications and outcomes for both the pregnant parent and the surviving twin. Consequently, it is recommended to make regular medical visits throughout the pregnancy to monitor it closely and effectively.