If twins are a boy and a girl, clearly they are fraternal twins, as they do not have the same DNA. A boy has XY chromosomes and a girl has XX chromosomes. Girl-boy twins occur when one X egg is fertilized with an X sperm, and a Y sperm fertilizes the other X egg.
In 99.9% of cases boy/girl twins are non-identical. However, in some extremely rare cases resulting from a genetic mutation, identical twins from an egg and sperm which began as male (XY) can develop into a male / female pair.
Fraternal twins, in which each of two eggs is fertilized by a different sperm cell, occur in about four of every 1000 births. About half of those result in male-female twin pairs.
Dizygotic (DZ) or fraternal twins (also referred to as "non-identical twins", "dissimilar twins", "biovular twins", and, informally in the case of females, "sororal twins") usually occur when two fertilized eggs are implanted in the uterus wall at the same time.
As per the university, MoMo twins are some of the rarest types of twins, making up less than one per cent of all births in the United States. According to Dr Gupta, MoMo twins account for “fewer than 0.1 per cent of all pregnancies and one per cent of identical twins”.
Septuplets (7)
The Frustaci septuplets (born 21 May 1985, in Orange, California) are the first septuplets to be born in the United States.
Monochorionic-monoamniotic twins are identical twins that share both a placenta and an amniotic sac. This is the rarest and highest risk form of twin pregnancies.
It's equally unsurprising that a Danish study found that twins are less likely to get married than non-twins. As twins have a partner from birth, the study suggests that they may not have the same desire for marriage as singletons.
Identical (i.e., monozygotic, or MZ) twins share 100 percent of their genes, whereas fraternal (i.e., dizygotic, or DZ) twins generally share only 50 percent of their genes.
They come from the same fertilized egg and share the same genetic blueprint. To a standard DNA test, they are indistinguishable. But any forensics expert will tell you that there is at least one surefire way to tell them apart: identical twins do not have matching fingerprints.
Multiple pregnancy usually happens when more than one egg is fertilized. It also can happen when one egg is fertilized and then splits into 2 or more embryos that grow into 2 or more babies. When one fertilized egg splits into 2, the babies are called identical twins.
As a parent of twins, I'm pretty sure that you know the answer to the question “which twin is older?” It is, of course, the child that was born first.
Vanishing twin syndrome was first recognized in 1945. This occurs when a twin or multiple disappears in the uterus during pregnancy as a result of a miscarriage of one twin or multiple. The fetal tissue is absorbed by the other twin, multiple, placenta or the mother. This gives the appearance of a “vanishing twin.”
"Twins married to twins who both have babies at the same time." Since identical twins share the same DNA, the children of two pairs of identical twins are legally cousins, but genetically more similar to siblings.
The risk of preterm labor and premature birth are heightened when there is more than one baby in the womb. 1 Other conditions such as preeclampsia, placental dysfunction, and twin-to-twin transfusion syndrome are more prevalent in twin pregnancy and increase the risk of an early delivery.
Trisomy 13 (also known as Patau syndrome) - MN Dept. of Health.
If the 12 – called duodecaplets – are all born alive they would represent a medical miracle and break the record of American mother Nadya Suleman, who recently gave birth to the world's longest-surviving octuplets.
The longest interval between the birth of twins is 90 days, in the case of Molly and Benjamin West, dizygotic (fraternal) twins born in Baltimore, Maryland, USA to parents Lesa and David West (all USA) on 1 January and 30 March 1996.
The worlds heaviest twins, with an aggregate weight of 12.58 kg (27 lb 12 oz), were born to Mary Ann Haskin (USA), of Fort Smith, Arkansas, USA on 20 February 1924.
Found at Lokomotiv in southern Siberia and dated to 7810-7640 cal BP, the woman in grave R11 is the earliest known instance of a mother of twins. She died at the age of 20-25 and was buried in prone and extended position with 15 mammuth teeth; her burial did not stand out in terms of funerary treatment or grave goods.