Splitting of the embryo may occur at any time during the first 2 weeks after fertilization, resulting in several forms of monozygotic twins.
About one-third of identical twins split soon after fertilisation and form completely separate twins. Like fraternal twins, these twins have separate placentas. The other two-thirds split after they attach to the wall of the womb.
Twins (non-identical) can be born at completely different times, sometimes even years apart.
Can an embryo split after 6 weeks? What about having twins happen after your first-trimester scan? It's very unlikely, as most twin embryos split within the first 2 weeks of fertilization.
The most accurate way to tell if twins are identical is through a DNA test. This can only be done after your babies are born. The placenta could also provide clues. If your first ultrasound scan is done before 14 weeks, it should be possible to tell accurately what kind of placenta your twins have.
Seeing twins at 6 weeks is definitely possible. The exact time twins can be detected depends on the type of twins, for example, if they're identical (from one egg) or not. At this stage, the presence of two yolk sacs can be seen, and separate heartbeats distinguished.
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.
Subsequently, Maria was induced in the hospital at 36 weeks and she gave birth to Katie, who weighed 5 lb, 10 oz. Hence, the total interval of time between the two twins was Eighty Seven (87) days which is an absolute medical miracle as both the babies and the mother are healthy and safe.
What is the likelihood of having more than one set of twins? If existing twins are identical the chance of having another set is the same as most women, about 1 in 250. If the twins are non- identical the chances of having twins again are much higher.
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).
Around one in three sets of twins is identical. This occurs because the fertilised egg divides in two while it is still a tiny collection of cells. The self-contained halves then develop into two babies, with exactly the same genetic information.
The reason why the egg splits is unknown – but the main theory has been that the process happens randomly. This is unlike the process whereby non-identical twins develop as a result of two separate eggs being fertilised by two sperm – a process that runs in families, unlike “monozygotic twinning”, researchers said.
In pregnancies with one placenta and two amniotic sacs, you will definitely have identical twins. Additionally, when your babies share a placenta, there is a greater risk for complications, such as twin-to-twin transfusion syndrome.
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.
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.
(Identical twins come from a single fertilized egg that splits in half, while fraternal twins occur when two different eggs are fertilized simultaneously). So, how many months apart are Irish twins? It's technically possible for two siblings to be as close as 9 or 10 months apart.
Identical twins have identical genetic programming. If lifestyle had no impact on aging, twins would age at the same rate. Differences in lifestyle and environment have long been suspected of influencing the pace at which we age, and a study published in Plastic and Reconstructive Surgery by Guyuron et al.
The median twin-to-twin delivery interval time was 19 min (range 2–399 min) and 68% of all second twins were delivered within 30 min.
While the typical definition of Irish twins is two children spaced 12 or fewer months apart, people do sometimes use the term more loosely to include children born 13, 14, or more months apart, particularly if the children end up in the same grade in school.
A couple of findings on ultrasound can help. If a first trimester ultrasound between weeks 8 and 13 shows that the fetuses share one placenta(or are “monochorionic”), the fetuses are identical more than 99% of the time. However, if the fetuses have two separate placentas, they can still be identical.
Twin baby development at 8 weeks
You can see them both on ultrasound now and your provider can detect heart beats. Their cells have been multiplying and are differentiating into different body systems and body parts, and their organs are forming rapidly.