Sean is a fact-checker and researcher with experience in sociology and field research. For the most part, twins and multiples share the same birthday. However, depending on the time of day the babies are born and how long the timespan is between each baby's birth, twins can be born on different days.
Twins with different ages
When this happens twice within one menstrual cycle, it's known as superfecundation. In this case, both fertilized eggs will develop, but one twin will be slightly older than the other.
Which twin is older? The oldest twin is the one who is born first. It doesn't matter whether twins are born vaginally or by C-section; the first one out of the womb is considered the oldest. This may be the baby who was labeled baby A during the ultrasounds, but it might not if the other one makes it out first.
They may have different lifestyles – exercise, smoking, drinking, nutrition, job stress, etc. As identical twins get older they may look more and more different, because they are exposed to more diverse environments. The science of epigenetics explains how these environmental influences can affect the genes.
Twins with different birthdays are rare, and the chance of twins being born in different years is 1 in 2 million, according to the news release by Natividad. Though the incident is rare, it's not the first time twins have been born in separate years.
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.
In rare cases, fraternal twins can be born from two different fathers in a phenomenon called heteropaternal superfecundation. Although uncommon, rare cases have been documented where a woman is pregnant by two different men at the same time.
It's a common misconception that twins skip a generation in families. There is absolutely no evidence, other than circumstantial, that twins are more likely to occur every other generation.
Twins not only have a bestie from birth — they also live longer than singletons. And those two factors may be related, according to new University of Washington research.
At age 7, the mean IQ score of twins was 5.3 points lower than that of singletons in the same family, and at age 9, the score was 6.0 points lower. The lower intelligence of twins in childhood may partly be a consequence of the reduced fetal growth and shorter gestations of twins, say the authors.
Medically, this 7-year defect is very rare. Twins are typically born with a bit of a delay — a few minutes to a few hours. Some even have separate birthdays, due to being born just before and just after midnight. The Zeitgest girls were not only born 7 years apart, but Ms.
A parasitic twin is an identical twin that has stopped developing during gestation, but is physically attached to the fully developing twin. The fully developed twin is also known as the dominant or autosite twin.
As expected, first-born twins had greater birth weight than second-born twins. With respect to height, first-born twins were slightly taller than second-born twins in childhood.
Twins (non-identical) can be born at completely different times, sometimes even years apart.
Most often, fetuses known in utero as twin A are also first born and thus retain their label. However, this is not always the case, such that the twin A newborn was previously labeled twin B in utero and vice versa.
The authors of the study believe the reason twins live longer may be because of the social support they provide each other, and the psychological and health benefits that come with that social connection. "There is benefit to having someone who is socially close to you who is looking out for you," Sharrow said.
At every age, identical twins had higher survival rates than fraternal twins. And, fraternal twins had higher survival rates than people in the general population. For men, the peak survival benefit of being a twin was at age 45.
Longer lives
When analyzing the data by gender, the researchers found that female identical twins lived, on average, about 63.4 years, whereas female fraternal twins lived about 61.4 years and the general Danish female population lived about 58.8 years, Sharrow said.
Monoamniotic-monochorionic Twins
These types of twins share a chorion, placenta, and an amniotic sac. This is the rarest type of twin, and it means a riskier pregnancy as the babies can get tangled in their own umbilical cords.
The quick answer to this question is that, in a twin pregnancy, it is the mother's genes that determine twins. First up, giving birth to identical twins is not genetic, but conceiving fraternal twins is. The mother may have the genetic trait of releasing two eggs in one menstrual cycle.
However, for a given pregnancy, only the mother's genetics matter. Fraternal twins happen when two eggs are simultaneously fertilized instead of just one. A father's genes can't make a woman release two eggs.
A double pregnancy, or superfetation, is extremely rare — in fact, there aren't even stats on how often it happens — but it's scientifically possible. We're not saying you should worry about it happening to you, just that you can't say that it's impossible.
"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.
Fraternal twins are formed when two eggs meet two sperm in the womb. Each is fertilized independently, and each becomes an embryo. With identical twins, one egg is fertilized by one sperm, and the embryo splits at some later stage to become two.