Vanishing twin
Encyclopedia
A vanishing twin, also known as fetal resorption, is a fetus
in a multi-gestation pregnancy which dies in utero
and is then partially or completely reabsorbed by the mother or twin.
The occurrence of this phenomenon is sometimes referred to as twin embolisation syndrome or vanishing twin syndrome (VTS), since the 1980s when twin pregnancies were made visible early on by means of ultrasound.
Occasionally, rather than being completely reabsorbed, the dead fetus will be compressed by its growing twin to a flattened, parchment-like state known as fetus papyraceus.
If the fetus is absorbed completely, there are usually no further complications to the pregnancy, other than first trimester
vaginal bleeding
. However, if the event occurs in the second or third trimester, serious complications may include premature labor, infection due to the death of the fetus, and hemorrhage. Even at the end of the pregnancy, a low-lying fetus papyraceus may block the cervix and require a cesarean to deliver the living twin.
The vanished twin can die owing to a poorly implanted placenta
, a developmental anomaly that may cause major organs to fail or to be missing completely, or there may be a chromosome
abnormality incompatible with life. Frequently the twin is a blighted ovum, one that never developed beyond the very earliest stages of embryogenesis
.
in the Brody School of Medicine and adjunct professor of biology at East Carolina University
, vanishing twins occur in up to one out of every eight multifetus pregnancies and may not even be known in most cases.
Patricia J. Sulak, M.D., has reported similar findings: "In reporting 300 early pregnancies evaluated by means of ultrasound noted 21 twins, one triplet, and one quadruplet. Only three pairs of twins survived to term (85.6% loss of the second twin), whereas the triplet pregnancy evolved into a normal twin gestation, and the quadruplet pregnancy reported here also evolved into a singleton gestation. Additionally, the triplet pregnancy reported here also evolved into a pregnancy diagnosed by means of ultrasound that evolved into a twin gestation. These very high resorption rates, which cannot be explained on the basis of the expected abortion rate, again suggest intense fetal competition for space, nutrition, or other factors during early gestation, with frequent loss or resorption of the other twin(s)."
Since it is hypothesized that in some instances vanishing twins leave no detectable trace at birth or before, it is impossible to say for certain how frequent the phenomenon is. It was hypothesized for a long time that non-right-handed and non-left-handed individuals may be the survivors of "mirror image" identical twinning.
"Vanishing" twins are frequently encountered in pregnancies created as a result of IVF. Ultrasound scans are taken very early in these pregnancies (5-8 weeks), so that, where a multiple conception has occurred, it frequently happens that more than one amniotic sac can be seen in early pregnancy, whereas a few weeks later there is only one to be seen and the other has "vanished".
Fetus
A fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth.In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization.-Etymology and spelling variations:The...
in a multi-gestation pregnancy which dies in utero
In utero
In utero is a Latin term literally meaning "in the womb". In biology, the phrase describes the state of an embryo or fetus. In legal contexts, the phrase is used to refer to unborn children. Under common law, unborn children are still considered to exist for property transfer purposes.-See also:*...
and is then partially or completely reabsorbed by the mother or twin.
The occurrence of this phenomenon is sometimes referred to as twin embolisation syndrome or vanishing twin syndrome (VTS), since the 1980s when twin pregnancies were made visible early on by means of ultrasound.
Occasionally, rather than being completely reabsorbed, the dead fetus will be compressed by its growing twin to a flattened, parchment-like state known as fetus papyraceus.
If the fetus is absorbed completely, there are usually no further complications to the pregnancy, other than first trimester
Pregnancy
Pregnancy refers to the fertilization and development of one or more offspring, known as a fetus or embryo, in a woman's uterus. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets...
vaginal bleeding
Vaginal bleeding
Vaginal bleeding refers to bleeding in females that is either a physiologic response during the non-conceptional menstrual cycle or caused by hormonal or organic problems of the reproductive system. Vaginal bleeding may occur at any age, but always needs investigation when encountered in female...
. However, if the event occurs in the second or third trimester, serious complications may include premature labor, infection due to the death of the fetus, and hemorrhage. Even at the end of the pregnancy, a low-lying fetus papyraceus may block the cervix and require a cesarean to deliver the living twin.
The vanished twin can die owing to a poorly implanted placenta
Placenta
The placenta is an organ that connects the developing fetus to the uterine wall to allow nutrient uptake, waste elimination, and gas exchange via the mother's blood supply. "True" placentas are a defining characteristic of eutherian or "placental" mammals, but are also found in some snakes and...
, a developmental anomaly that may cause major organs to fail or to be missing completely, or there may be a chromosome
Chromosome
A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...
abnormality incompatible with life. Frequently the twin is a blighted ovum, one that never developed beyond the very earliest stages of embryogenesis
Embryogenesis
Embryogenesis is the process by which the embryo is formed and develops, until it develops into a fetus.Embryogenesis starts with the fertilization of the ovum by sperm. The fertilized ovum is referred to as a zygote...
.
Frequency
According to Charles Boklage, a professor in the Department of PediatricsPediatrics
Pediatrics or paediatrics is the branch of medicine that deals with the medical care of infants, children, and adolescents. A medical practitioner who specializes in this area is known as a pediatrician or paediatrician...
in the Brody School of Medicine and adjunct professor of biology at East Carolina University
East Carolina University
East Carolina University is a public, coeducational, engaged doctoral/research university located in Greenville, North Carolina, United States. Named East Carolina University by statute and commonly known as ECU or East Carolina, the university is the largest institution of higher learning in...
, vanishing twins occur in up to one out of every eight multifetus pregnancies and may not even be known in most cases.
Patricia J. Sulak, M.D., has reported similar findings: "In reporting 300 early pregnancies evaluated by means of ultrasound noted 21 twins, one triplet, and one quadruplet. Only three pairs of twins survived to term (85.6% loss of the second twin), whereas the triplet pregnancy evolved into a normal twin gestation, and the quadruplet pregnancy reported here also evolved into a singleton gestation. Additionally, the triplet pregnancy reported here also evolved into a pregnancy diagnosed by means of ultrasound that evolved into a twin gestation. These very high resorption rates, which cannot be explained on the basis of the expected abortion rate, again suggest intense fetal competition for space, nutrition, or other factors during early gestation, with frequent loss or resorption of the other twin(s)."
Since it is hypothesized that in some instances vanishing twins leave no detectable trace at birth or before, it is impossible to say for certain how frequent the phenomenon is. It was hypothesized for a long time that non-right-handed and non-left-handed individuals may be the survivors of "mirror image" identical twinning.
"Vanishing" twins are frequently encountered in pregnancies created as a result of IVF. Ultrasound scans are taken very early in these pregnancies (5-8 weeks), so that, where a multiple conception has occurred, it frequently happens that more than one amniotic sac can be seen in early pregnancy, whereas a few weeks later there is only one to be seen and the other has "vanished".
External links
- Vanishing twin at eMedicine.com
- Vanishing twin occurrence in India
- Photographic evidence of a vanished twin found on the placenta after delivery of the surviving twin
- LNC Newsletter - Vanishing Twin Syndrome and Fetus Papyraceus
- A review in Human Reproduction Update
- 50 articles about vanishing twin phenomenon in PubMed
- Article by Kramer with useful references
- Attachment Issues Associated with the Loss of a Co-twin Before Birth