It has been well documented that twins are shorter at birth than are singletons and that a difference in body height remains for at least a few years after birth (1–4).
Infants from twin pregnancies are generally born smaller than singletons; therefore, it has been suggested that twins represent a naturally occurring model of IUGR.
Multiples do tend to be born smaller than single babies. But it's not because their growth rate is necessarily slower — in fact, for twins, it's about the same as any other baby's until about weeks 30 to 32, when they do slow down a tad, since they're competing more for nutrients.
Although the majority of monozygotic twin pairs achieve an identical height, a proportion of them are discordant. Because monozygotic twins completely share their genome, differences in their adult height are not due to heritable factors.
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).
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.
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.
Conclusion: Twin fetus experience slowing of growth beginning at ∼26 weeks of gestation and a greater degree of asymmetric growth pattern compared with singletons. These findings suggest that the slower growth of twins may reflect a state of "relative growth restriction" compared with singleton gestations.
An analysis of the total study population using generalized estimating equations showed that the twins were 0.6 cm (95% confidence interval: 0.4, 0.7) shorter than were the singletons after adjustment for a series of background factors.
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.
The average length for newborns is between 19 and 20 inches long – to be exact, 19 inches for female babies and 19.75 inches for male babies. That said, healthcare providers consider a newborn length anywhere between 18.5 and 20.9 inches to be normal for full-term babies.
Fraternal Twins Boy and Girl
Since conception happened for each egg, each egg carries the sex chromosome of the father. A girl has XX chromosomes while a boy has XY chromosomes. A boy-girl combination is the most common form of these kind of twins.
Most twins, triplets and more grow and develop along roughly the same lines as their singleton peers – even those who start out much smaller will catch up in time.
Twins are more or less equally likely to be female or male.
As a general rule of thumb, your height can be predicted based on how tall your parents are. If they are tall or short, then your own height is said to end up somewhere based on the average heights between your two parents. Genes aren't the sole predictor of a person's height.
Twin delivery, on average, occurs around 35 to 36 weeks. Triplets and quadruplets may come even sooner. Moms of singletons, on average, deliver at 39 weeks. Since many twin births happen early, the average twin arrives weighing about 5 1/2 pounds.
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.
The researchers found that twins at age 7 had I.Q.'s an average of 6.6 points lower than those of their singleton brothers and sisters, and that by age 9 their average I.Q. was 6.9 points lower.
“Having twins is not twice as hard—it's exponentially more difficult,” says Natalie Diaz, author of What To Do When You're Having Two and CEO of Twiniversity, a global support network for parents of twins.
It is estimated that 1 in 250 natural pregnancies will naturally result in twins. While twin pregnancies can happen by chance, there are some factors that may increase your odds of having two babies at the same time. Let's learn about twins!
Having two babies at a time is associated with a longer life, according to a new study. But that's not because doubling up on dirty diapers increases life span; instead, moms of twins are physically stronger in the first place.
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.
It is likely that twins' awareness of one another starts sooner than seven or eight months of age. An article by the late doctor, T. Berry Brazelton, observed that at age three to four months, an infant identical female twin seemed disoriented when her sister was removed from the room.
Using the family-based adult sample, no differences in IQ scores were found between twins and their singleton siblings.