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.
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.
However, many birth order experts agree that twins tend to organize themselves according to their overall place within the family. 2 For example, if they have one older sibling, they will both exhibit characteristics of a second born. If they are the oldest, they will adopt some traits of firstborns.
In addition, previous studies have shown that first-born twins are, on average, taller and heavier than second-born twins until adolescence (Silventoinen et al., 2007; Pietiläinen et al., 2002).
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.
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. It sounds like fraternal twins do indeed run in your family!
FSH stimulates the ovaries to produce eggs, and these gene variations likely contribute to hyperovulation — the release of more than one egg in a menstrual cycle. The genetic predisposition for twins only affects gestational parents.
Classically, the bigger twin is the more physically dominant. It's basic human nature, and particularly applicable to boys as they hit puberty. It happens often with singleton siblings too… the older is bigger and enforces him/herself through physical dominance.
There is one particular power though which twins possess, longevity. Fraternal twins live longer than singletons and identical twins longer still. Male identical twins on average, saw the most benefit.
Monoamniotic-monochorionic Twins
This is the rarest type of twin, and it means a riskier pregnancy as the babies can get tangled in their own umbilical cords. If you have monoamniotic-monochorionic twins, your healthcare provider will monitor your pregnancy closely.
There is no right or wrong answer, it's a personal preference. Some chose to be completely open or tell their twins to give a “smaller” twin leverage if he/she is older. Other choose not to tell so that they don't bicker about the subject or the dominate “older” twin doesn't have more leverage.
Barring pregnancies that result from assisted reproductive technology, dizygotic twins are far more common than monozygotic twins and account for 70 percent of all twin gestations.
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.”
Non-identical (dizygotic) twins happen when 2 separate eggs are fertilised and then implant into the womb (uterus). These non-identical twins are no more alike than any other 2 siblings. Non-identical twins are more common.
The hardest thing about having twins is...
“Managing the movement of two babies. Carrying them both up and down the stairs, getting them into the car, etc.” —Simeon R. “Often having to make one baby wait!” —Catharine D. “Being outnumbered—the logistics of two on one is definitely the hardest.
Factors that increase the chance of twins include: consuming high amounts of dairy foods, being over the age of 30, and conceiving while breastfeeding. Many fertility drugs including Clomid, Gonal-F, and Follistim also increase the odds of a twin pregnancy.
Because boys have the sex chromosomes XY, they must inherit their Y chromosome from their father. This means they inherit all the genes on this chromosome, including things like sperm production and other exclusively male traits.
Since identical twins share the same DNA, the children of two pairs of identical twins are legally cousins, but genetically more similar to siblings.
This is supported by a Dutch study of adult twins, which found no significant difference in IQ between singletons and twins from the same families.
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.
Vaginal Birth of Twins
The good news is that even though you have two babies, you only have to labor once. Once the cervix is open, each baby will have its own pushing stage. This means you will have to push twice, but the majority of the time the second twin is born much more easily than the first.