The phenomenon of having a twin grow inside of you is known as fetus-in-fetu (FIF). This condition is incredibly rare and only occurs in approximately 1 in of every 500,000 live births. Fetus-in-fetu occurs when an identical twin embryo is joined in the mother’s womb and is forced to remain partially developed inside of their co-twin.
The twin embryo will often be wrapped in a thin membrane and have its own network of blood vessels, allowing it to receive nourishment from the host twin. The partially developed twin will typically be located in the abdomen or chest of its host twin, and in most cases can be easily seen on an ultrasound.
During childbirth, the complete fetus is usually removed via a cesarean section. Once the fetus-in-fetu is removed, it is generally seen as a complete but nonviable fetus. Depending on how long the fetus survived in its host twin’s womb, the tissue may or may not appear histologically normal.
In some cases, the fetus will display signs of abnormality or malformation, due to it not receiving the proper nutrition or medications that would have been provided to a normal pregnancy.
Fetus-in-fetu is an extremely uncommon congenital anomaly, and it is still largely unknown what causes it. Researchers do know, however, that it is not hereditary and can occur with any set of fraternal or identical twins.
It is incredibly difficult to diagnose prenatally, and therefore FIF is usually discovered during birth or postmortem examination.
Table of Contents
What does it mean when a twin is absorbed?
When a twin is absorbed, it means that one of the identical twins has incorporated the physical and/or genetic characteristics of the other twin into its own special identity. This can happen due to the shared placenta in the womb, where one twin can literally absorb the other.
This can lead to the surviving baby having some characteristics that appear to belong to the other twin such as physical features, blood type, or even a genetic mutation. In some cases, the surviving twin will even display the extra limb or organ of the other.
In other cases, the twin that is absorbed can remain as its own distinct entity, while the characteristics of the absorbed twin become a part of the other twin. In either case, the twins are still considered to be unique individuals in their own right, even though they may be made up of genetic material from both twins.
What happens if you absorb your twin?
If someone attempts to absorb their twin, it could result in a life-threatening or even fatal situation. When twins share the same environment during gestation, they are able to form a unique type of physical connection known as ‘twin fusion’.
This connection is essentially a single umbilical cord, wherein the two twins can essentially share the same blood flow and nutrients from one another. In some cases, a twin who is weaker or smaller compared to the other may essentially ‘absorb’ its counterpart.
This is known as ‘vanishing twin syndrome’, and can happen if the absorbed twin does not receive the necessary nutrients it needs to survive. As a result, the unborn baby may become bloated as the remaining cells from the absorbed twin will be incorporated into the remaining baby’s body.
Symptoms of vanishing twin syndrome could include an enlarged abdomen, increase in weight, and changes in the shape of the head due to excess fluid build-up. In rare cases, it can be life-threatening if the larger or stronger twin’s organs become overstretched due to the absorption.
Ultimately, if someone attempts to absorb their twin in their mother’s womb, it could result in serious consequences. It is therefore important to ensure that proper prenatal care is given to ensure both twins’ health and wellbeing in the case of a multiple gestation pregnancy.
How common is an absorbed twin?
Absorbed twins, also known as conjoined twin resorption, are an extremely rare occurrence, and the exact prevalence is unknown. It is estimated that one in 500,000 pregnancies results in an absorbed twin, but this statistic is not definitively established.
In some cases, one twin is partially or completely absorbed by the other in the early stages of the pregnancy due to unequal division of the fertilized egg. This results in a unique situation where one fetus will receive more nutrients from the mother than the other.
When this occurs, the dominant twin will absorb some of the tissue and organs of the weaker twin, resulting in a single embryo with parts of the absorbed twin. Most absorbed twins are not discovered until after delivery, since the absorbed twin does not often show up on ultrasound images.
It is also possible for an absorbed twin to be mistaken for a “vanishing twin” due to its lack of presence on ultrasound images.
Can humans absorb their twin?
No, humans cannot absorb their twin. Though it is theoretically possible for two fetuses to fuse during development and share a single placenta, such instances are very rare. A study published in 2015 found that only 1 in every 10,000 humans has remnants of a twin inside their body.
This is known as chimerism, and while it can cause issues like irregular hormone production and organ malfunction, it doesn’t mean that the surviving twin has ‘absorbed’ the other. In some cases, the remnants of the vanished twin can remain undetected until a person undergoes medical testing in late adulthood.
Is a vanishing twin considered a miscarriage?
Yes, a vanishing twin is considered a miscarriage. A vanishing twin occurs when one fetus in a multiple pregnancy has a spontaneous miscarriage during the first trimester. In some cases, the other twin may be indistinguishable during follow up ultrasounds and it is only known that a miscarriage occurred due to changes in hormone levels.
Vanishing twins may be caused by genetic factors, chromosomal abnormalities, or other factors. The causes of a vanishing twin are difficult to pinpoint, which is why it is considered a miscarriage. This type of pregnancy loss can be difficult to process, especially if the other twin is still viable.
It is important for those affected to seek medical and emotional support after a vanishing twin is diagnosed.
Do you bleed with a vanishing twin?
Yes, it is possible to bleed with a vanishing twin, which is a term for when one of the fetuses in a twin pregnancy is miscarried or does not develop in the womb. This is also known as vanishing twin syndrome when both fetuses are lost, but if only one is not developing then it is called a vanishing twin.
Bleeding associated with a vanishing twin is usually seen when the fetus is lost during the first trimester of pregnancy and may appear as light spotting or as a heavier bleeding with clots. Depending on the amount of fetal tissue left in the uterus, cramps similar to menstrual cramps may also be experienced.
In some cases, the remaining fetus will continue to develop normally, while in others the mother may have to undergo further medical tests to ensure that the pregnancy is healthy. If the amount of bleeding is high, it is important to seek medical attention to ensure that everything is okay.
Can vanishing twin happen after heartbeat?
Yes, it is possible for a vanishing twin to occur after a heartbeat has been detected. This occurs when a twin pregnancy is detected but one of the twins ultimately fails to continue developing, resulting in the fetus becoming reabsorbed into the mother’s body.
The pregnancy can continue with a single viable fetus, but due to the presence of the vanishing twin, the pregnancy can become more complicated. In some cases, the mother may need to be closely monitored for signs of infection or other complications due to the presence of the vanishing twin.
As a result, it is important to seek medical advice if any fetal heartbeat is detected and to discuss any concerns with a physician.
What causes fetal resorption?
Fetal resorption, or often known as “pregnancy loss”, is a very common phenomenon in pregnancies. It is typically caused by the death of the embryo or fetus, and the body’s subsequent absorption of the deceased matter.
Including chromosomal abnormalities, maternal immune responses, placental abnormalities, bacterial or viral infections, hormonal imbalances, exposure to hazardous substances, physical trauma, and nutritional deficiencies.
Chromosomal abnormalities are one of the more common causes of fetal resorption. When a fetus has a chromosomal abnormality, the body will naturally reject it, leading to its death. This process is known as a spontaneous abortion.
Maternal immune responses can also cause fetal resorption. In this case, when the woman’s immune system perceives the fetus as a foreign body, it will try to reject it, causing the fetus to die and then be reabsorbed.
Placental abnormalities can also be responsible for fetal resorption. This is often due to a variety of factors, such as abnormal development of the placenta, which restrict the fetus’ access to oxygen and nutrients or cause physical trauma to the fetus.
Bacterial or viral infections can also lead to fetal resorption. When the fetus is exposed to the bacteria or virus, it can cause serious complications, leading to its death and eventual absorption by the mother’s body.
Hormonal imbalances can cause fetal resorption as well. When levels of certain hormones (such as cortisol, estrogen, and progesterone) are not at their proper levels, it can lead to a decrease in the levels of oxygen and nutrients available to the fetus, resulting in its death.
Exposure to hazardous substances can also cause fetal resorption. Certain toxins, such as lead and mercury, can be toxic to the developing fetus, leading to its death and absorption by the mother’s body.
Physical trauma can also lead to fetal resorption. In some cases, a mother’s physical condition can affect the fetus, such as an injury to the abdomen or fall. These situations can lead to the death of the fetus and then reabsorption by the mother’s body.
Nutritional deficiencies can also be a factor in fetal resorption. When the mother does not have access to adequate nutrition, the fetus may die and then be reabsorbed. This is often seen in situations where the mother has an eating disorder or is malnourished due to poverty or disease.
In conclusion, fetal resorption is most often caused by chromosomal abnormalities, maternal immune responses, placental abnormalities, bacterial or viral infections, hormonal imbalances, exposure to hazardous substances, physical trauma, and nutritional deficiencies.
It is important for women to understand the possible causes of fetal resorption so that they can take the necessary steps to prevent it.
How rare is a chimera human?
Chimera humans are incredibly rare, with only a handful of cases ever reported. The phenomenon of chimerism refers to the presence of two genetically distinct cell populations in the same individual, and humans exist in a range of chimeric form.
The majority of cases occurring in humans involve a mixture of male and female cells, or two different types of female cells. Some cases have also been reported in which the chimera is composed of cells with different chromosomal constitutions, including two different types of cells in one organ.
Because chimera humans are so rare, and because the condition may not manifest in any visible symptoms, it can be difficult to accurately track and tally the number of reported cases. Most reports suggest there are only around 6 known cases of chimeric humans worldwide.
It is important to note that chimeric conditions can occur naturally in both sexes, though they are all technically considered a type of intersex or gender variant situation.
Though there have been some reports of human chimerism over the past few decades, the condition remains largely mysterious and misunderstood. Due to its rarity and the lack of research, it is impossible to accurately assess the prevalence of the condition.
However, it is likely that chimera humans are much more common than recorded and that many cases are likely to go undiagnosed or even unnoticed.
Can a vanishing twin survive?
In rare cases, vanishing twins can survive. This is when one twin vanishes due to an early embryo loss, but the other survives. It is estimated that up to 30% of all twin pregnancies will result in one vanishing twin.
In most cases, the vanishing twin is absorbed by the other twin, the mother, or even the placenta. In some cases, the vanishing twin may survive, but be either much smaller or miscarried. In some rare instances, the surviving twin may develop medical complications due to the presence of the vanishing twin.
For instance, the surviving twin may experience chromosomal abnormalities, or developed tissue or organ damage due to the presence of the vanishing twin. Additionally, the twin may suffer from anemia, blood clots or low birthweight.
It’s important to consult with a doctor if you have questions or concerns about a twin pregnancy.
How do you know if a twin was absorbed?
It can be difficult to know if a twin was absorbed in the womb because the definitive signs are rarely visible after birth. However, there are a few signs and symptoms that may indicate the possibility that a twin was absorbed in the womb.
For example, higher than normal levels of hormones, such as human chorionic gonadotropin (hCG) and alpha-fetoprotein (AFP), may be present in certain blood tests. Ultrasound imaging may also reveal remaining tissue from a twin or extra body parts, such as arms or legs, despite the fact that the infant has been born with only one body.
Additionally, the surviving twin may experience deformities or abnormalities due to the material and space that the other twin had occupied. In severe cases, the surviving twin may have severely underdeveloped organs (depending on the amount of material that was lost).
Therefore, it is important to seek medical attention if any of these signs or symptoms are present to determine the cause.
What Week Do twins absorb each other?
Twins usually begin to absorb each other in the 8 to 12th week of gestation, which is when most of their organs are starting to develop. During this time, an ultrasound might be able to detect the amniotic fluid and fluid found between the two fetuses, which shows that they are absorbing each other.
After this period, the two fetuses will still appear separate on an ultrasound and any apparent absorption is no longer detectable. With prenatal medical care, the early detection of the absorption process can help doctors assess the risk of complications and intervene if necessary.
What is the rarest combination of twins?
The rarest combination of twins are conjoined twins. Conjoined twins occur when, in the early stages of development, an embryo only partially separates to form two individuals. These twins will be physically connected at some point on their bodies, most often at the chest, stomach, or pelvis.
This type of twinning is very rare, occurring in only one in 200,000 pregnancies. Conjoined twins occur more often in female births and more frequently in certain ethnic populations, such as Southeast Asian and African populations.
There is a variety of conditions caused by different degrees of conjoined twins. The condition can range from partially conjoined twins who can be surgically separated, to completely conjoined twins who share vital organs such as the liver, heart, or intestines and will have an even lower rate of survival.
Conjoined twins are typically born prematurely, and the prognosis for each twin can vary greatly, from complete separation to one or both of them not surviving.
Which type of twin births are most common?
The most common type of twins are dizygotic, also known as fraternal twins. These twins form when two separate eggs are fertilized by two separate sperm and then implant in the mother’s uterus. Fraternal twins make up about 70% of all twin pregnancies and can be either the same or different genders.
Fraternal twins can also be a combination of two different ethnicities and/or hair, eye and skin color. When twins are the same gender, they can either be identical or fraternal.
Identical twins form when a single fertilized egg splits into two and results in a pair of genetically identical babies. They are relatively rare, accounting for only 30% of twin pregnancies, and they always develop with the same gender.
Identical twins may look very alike on the outside, but they each have their own unique fingerprints.
There is also a third, rarer form of twinning known as “half-identical” twins. These form when a single fertilized egg splits partially and then each half is fertilized by a separate sperm. This form of twinning is relatively rare and accounts for only 1 in 100,000 births.
