Being told that you’re expecting twins can come as a shock. Some mothers may be thrilled, and even relieved, that they are carrying healthy babies and have created an instant family unit. Others may dread the increased parenting skills required, and the extra demands on finances, logistics and their time.
Once parents have got their heads round the fact that they will soon have more than one baby, the next major question is: will they be identical? Birth rate statistics for identical twins have remained stable over the years, despite the overall increase in multiple births since the late 1980s. The odds of having identical twins is about 3 in 1000, whereas the birth rate for all twins is about 33 in 1000.
If twins are identical, they are known as monozygotic. This means that they were formed from a single fertilised egg, which went on to split into separate embryos. They may or may not share a placenta. It is not always clear in utero whether twins are identical or not. The placentas of non-identical twins may fuse together in the womb giving the appearance of a single placenta making them appear to be identical. Conversely, approximately one-third of identical twins have separate placentas making them appear non-identical.
Gail and Chris Evans were told by their gynaecologist during a routine scan that their twin boys were non-identical. “The scan showed that the babies were in two separate sacs and that there were two placenta present”, said Gail.
By around 2 years of age, physical features – such as hair and eye colour, ear shape, teeth formation, hand and feet appearance – can usually indicate whether or not twins are identical. If such changes aren’t apparent, then zygosity determination can help. This DNA test is the only way to conclusively determine whether twins are identical or not.
As the Evans twins grew up, people always struggled to tell the boys apart. To clarify the matter once and for all, the family decided to arrange a zygosity test with AlphaBiolabs. This non-invasive twin test involves analysing tiny amounts of DNA from each of the brother’s cheek cells. Specific markers present in repeat sections of DNA are examined and compared; identical twins share the same DNA profile whereas non-identical twins have different DNA profiles.
“We couldn’t believe it!”, said Gail. “For 26 years we believed that our twin boys were non-identical. To our surprise the results confirmed that the boys are identical. This has ended years of speculation within the family and has provided us with conclusive scientific proof.”