The number of women having multiple births in the UK has increased year on year since 1980. There are numerous reasons for this and include:

  • the increased use of fertility treatment. On average, one in 10 IVF pregnancies results in a multiple birth.
  • mothers waiting later to start their families. Women aged 45 and over are most likely to have a multiple birth: in 2015, 102.4 out of every 1000 women giving birth in this age group had a multiple birth.1
  • maternal history. A mother is more likely to have multiple births if there is a history of multiple pregnancies in her family.
  • An increase in obese mothers. Research has shown that obesity can lead to more multiple births.

Whether or not the twins, triplets, quadruplets and higher multiple babies are identical depends on how the babies were formed. Non-identical siblings are the result of separate fertilised eggs. These babies are no more alike than any other brothers or sisters, and may be both male, both female, or one of each. They share DNA in common as in the case of siblings from different births.

Identical siblings are formed from a single fertilised egg, which went on to split into separate embryos. This means their DNA is exactly the same.

An easy way to determine whether multiple children from the same birth are genetically identical or not is by zygosity twin testing. The test involves analysing tiny amounts of DNA from inside each sibling’s mouth. Specific markers present in repeat sections of DNA are examined. These 24 Short Tandem Repeat (STR) loci include the Amelogenin (gender) locus. The DNA seen at each of these STR loci is compared between the tested individuals; identical siblings will share the same DNA profile whereas non-identical siblings will have different DNA profiles.

An increasing and novel use of a DNA zygosity profile is as a unique gift idea for multiple birth parents and/or their children. For more information on Zygosity twin testing, please contact AlphaBiolabs on 0333 600 1300; email:;