In the majority of vaginal births, Baby A is born first. But occasionally the twins switch positions at the last minute, and Baby B emerges first, as further noted by the Stanford Medicine News Center. Still, the birth order is relatively straightforward.
So the firstborn is really the youngest. Answering the “which twin is older” question from strangers is one thing. Fielding the questions from friends, family, or the twins themselves is another story. You should discuss as a couple your approach for answering this question with people you know.
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.
Most twin, triplet or more babies will be slightly different in size, but sometimes 1 baby is significantly smaller than the other/s. This is called 'selective' fetal growth restriction.
Overall, the differences in height and BMI between first and second born twins were modest even in early childhood, while adjustment for birth weight reduced the birth order differences but did not remove them for BMI.
Ultrasound exams are performed regularly to calculate the twins' weights and watch their growth and fluid levels. Although the smaller twin's growth may be somewhat restricted, in most cases the smaller twin will grow well enough to function normally.
Abstract. Despite the clinical impression that firstborn twins do better than second-born twins, recent reports have shown no difference in perinatal mortality between them.
Dizygotic twin pregnancy – where two eggs are fertilised in the same cycle (65% of all twins). These are sometimes called fraternal twins as they have the same genetic makeup as do brothers and/or sisters.
Fraternal twins live longer than singletons and identical twins longer still. Male identical twins on average, saw the most benefit. The rarity of twins has inspired many myths about them.
Identical twins are almost always the same sex, although there are some rare exceptions to this rule. Because identical twins occur when a single fertilized egg splits and forms two embryos, each embryo has the same chromosomes (usually, XX for girls or XY for boys).
Identical twins
Identical (monozygotic) twins happen when a single egg (zygote) is fertilised. The egg then divides in 2, creating identical twins who share the same genes. Identical twins are always the same sex, so if your twins are identical, you'll have 2 girls or 2 boys.
Anita Makhtur, previously childless Indian woman, gave birth to twin boys in December 2009, at the age of 51, after IVF treatment. She was unable to get pregnant for 23 years because of fibroma uteri and had two unsuccessful attempts of IVF. She is probably the oldest woman who had IVF using her own unfrozen oocytes.
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.
Twins can change positions, but if they're head-down at 28 weeks, they're likely to stay that way. When delivering twins vaginally, there is a risk that the second twin will change position after the delivery of the first. Research shows that second twins change positions in 20 percent of planned vaginal deliveries.
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 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.
Dizygotic (DZ) twins, also called fraternal twins, occur when two egg cells are each fertilized by a different sperm cell in the same menstrual cycle. DZ twins are about twice as common as MZ twins, and they are much more likely to run in families.
However, few genes appear to be definitively linked to hyperovulation, so it could just be that genetics in general on the mother's side contribute to the probability of having fraternal twins. Heredity on the father's side, on the other hand, does not increase a couple's odds of having twins.
The best students tend to be the oldest of three children, with a brother less than two years younger than them and a sister at least five years younger. Birth order studies are a dime a dozen, but scientists have spilled far less ink on sibling configurations.
In prenatal ultrasounds, the baby positioned lowest in the uterus is given the designation of “Baby A.” Under this convention, Baby A will likely be born first in a vaginal delivery. However, about 75 percent of twins are delivered by cesarean section.
While the average single baby weighs 7 pounds at birth, the average twin weighs 5.5 pounds. Triplets typically weigh 4 pounds each, and quads weigh 3 pounds each.
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.”
Some identical twins can have different heights and weights. This is because height and weight are controlled by what you eat as well your DNA. Differences in diet can start earlier than you might imagine. When the twins are growing inside the uterus, there can be differences in how well they connect to the placenta.