Birth Order and Twins The babies' order of birth is determined by their position in the womb, which can change throughout pregnancy. In some cases, which baby is born first depends on how the mother delivers; the order might be switched if the mother had a Cesarean section rather than vaginal delivery.
For vaginal delivery of both infants, the twins decide birth order by their placement in the uterus. Once the babies are large enough to stay in one position in the womb, the twin lowest in the uterus is known as Baby A and the one furthest from there is Baby B, according to the Stanford Medicine News Center.
This is why fraternal twins run in families. However, only women ovulate. So, the mother's genes control this and the fathers don't. This is why having a background of twins in the family matters only if it is on the mother's side.
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.
A phenomenon known as superfetation can occur when a second egg gets released and fertilized after a person is already pregnant. 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.
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.
People over 30, and particularly those over age 35, are more likely to conceive twins. 4 This is because the level of follicle-stimulating hormone (FSH) rises as birthing parents get older. FSH is responsible for the development of eggs in the ovaries before they are released.
Certainly, there are many examples of twin sets where the firstborn twin is a dominant leader and the secondborn is a subdued follower.
Despite the clinical impression that firstborn twins do better than second-born twins, recent reports have shown no difference in perinatal mortality between them. In order to evaluate differences in twins, more sensitive means than perinatal deaths are necessary.
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.
While men can carry the gene and pass it on to their daughters, a family history of twins doesn't make them any more likely to have twins themselves. 3 But, if a father passes on the "twin gene" to his daughter, then she may have a higher chance than normal of having fraternal twins.
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.
Are twins hereditary? Yes, some types of twins are hereditary, meaning that twins run in families. Heredity on the mother's side ups a couple's odds of conceiving fraternal twins. Fraternal twins are two babies from two different eggs that were released from the ovaries simultaneously.
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.
When people refer to Irish twins, it's important to recognize that although the siblings are close in age, they are not actually twins. In other words, they were not born during the same gestational period. Calling them Irish twins is just an informal way of classifying siblings that are born close together.
All fraternal twins are di/di, but identical twins can also be di/di. How is this possible? With a fraternal twin pregnancy, separate eggs are individually fertilized by two different sperm cells creating two individual zygotes. Each zygote will have its own placenta and amniotic sac.
Many people believe twins skip a generation, but that's just a myth. The idea that twins skip generations likely comes from the fact that the genetic factors contributing to twins only come from the gestational parent's side.
Many authorities recommend that monoamniotic twin pregnancies be delivered by elective cesarean as early as 32 to 34 weeks of gestation due to the risk fetal demise secondary to cord entanglement. Continuous electronic fetal monitoring of both fetuses is required throughout labor and delivery.
The first wife (died ante 1770), of Feodor Vassilyev (b. 1707–c. 1782), a peasant from Shuya, Russia, gave birth to 16 sets of twins.
What Is Oldest Child Syndrome? Oldest Child Syndrome is believed by some to be evidence of common characteristics that can be attributed to birth order. These traits of first-born children include a sense of entitlement, responsibility, and ambition.
For women born 1870-1899, moms of twins averaged reproductive spans of 14 years 11 months versus 14 years for singleton moms. Both results were statistically significant. Moms of twins also were older at the time of their last birth.
In fact, one British study tested ESP potential among identical twins and found that they were correct about 25% of the time, the same as any other siblings. There is one particular power though which twins possess, longevity. Fraternal twins live longer than singletons and identical twins longer still.
At three months:
The three-month stage marks the end of the “fourth trimester” and your twins can better adapt to life outside the womb. For one thing, they'll sleep in longer stretches of about three- to four-hour chunks.
Twins are more or less equally likely to be female or male.
Mixed-gender twins are the most common type of fraternals, some 50 percent are boy-girl. To understand this combination: Males have XY chromosomes, females have XX chromosomes.