Where Did That Come From. A regular column that examines the history and origins of a particular medical topic.

Earlier this year we welcomed the birth of twins into the Danish royal family. Naturally it created world-wide media frenzy, being especially frenzied in Australia with Princess Mary being one of our own, and a popular lady at that. Twins are not all that common but, when combined with royalty, such occasions are few and far between.

Overall twins occur about once in every 77 births. The memories of ordinary folk generally do not go back longer than the great-grandparents, so the chances of knowing about such family events more than a 100 years or so ago are remote.

But because they are well recorded in history the pregnancies of at least one family have been closely monitored for centuries - the British Royal Family. Though, like most royal families of Europe, the Danish and British Royals are related, it is the latter which has a longer recorded lineage, so let's look at the twin history in that family.

Since 1066 when William of Normandy was crowned the first king of all England there have been 160 or so pregnancies in the royal family. That being so, statistically you would expect there to have been two sets of twins during that time; that is exactly the case. Regrettably, both events ended in disaster. One set was delivered by Queen Anne before she was crowned and the other to the consort of William IV, Adelaide, before he became king in the early part of the 19th century.

Before Scotland and England joined under a common ruler in 1625, the Scottish queens had also produced two sets of twins - so there have been four sets all told in the British Isles.

There are two types of twins, identical and non-identical, or fraternal. Identical twins are produced by a splitting of the ovum at conception. They are always the same sex and the gynaecological event is a chance and not inherited occurrence. Fraternal twins result from the release of two ova by the mother and can be an inherited characteristic of the parents and not chance. They can be the same or different sexes, and are no more alike than ordinary siblings. As we all know, our Princess Mary had non-identical twins.

Let's look first at the British regals' obstetrical history.
Queen Anne (1665-1714) had lots of pregnancies, 17 in all. Her husband, Prince George, who happened to be from Denmark and who, though regarded as a rather colourless and dull man who has made little impact on history, seems to have fulfilled his conjugal obligations. Tragically, most of the babies, including the twins, were stillborn and of those who did survive none lived to adulthood. The twins were Anne's 13th pregnancy and they died on 20 September 1696. The cause of the deaths was probably placental insufficiency.

Queen Adelaide went into premature labour during the seventh month of her pregnancy in April 1822. In an era of poor obstetrical care, the babies were too small to survive. If they had survived, the first born would have succeeded to the throne. In any event William's younger brother, Edward Duke of Kent, had a legitimate daughter in 1819 and it was she who eventually succeeded to the British throne in 1837 to become Queen Victoria
Looking to Scotland, a royal twin who did survive to serve as king was the son of James I of Scotland. His wife, Queen Joan, had delivered twin boys on 16 October 1430 at Holyrood Castle, Edinburgh. Sadly one child, Alexander, died later in his youth but his brother, James, known as ‘James of the fiery face' because of a birthmark, went on to become James II. In 1460 he had the great misfortune to be blown to bits by one of his own cannons while laying siege to Roxburgh Castle which at the time was held by the English.

The other multiple birth north of the border involved that tragic, though romantic, figure from British history, Mary Queen of Scots. Her life story was like an action-packed soap opera.

For reasons too complicated to outline here, her first husband, Henry Stewart (Lord Darnley), was murdered on 10 February 1567 in an explosion at his house which was probably instigated by the Earl of Bothwell, a man who had recently enjoyed the queen's favour. Mary herself may have been implicated. Anyway, Bothwell was acquitted and he and Mary ran off together and got married on 15 May. Opponents to the union captured them in June. Bothwell escaped, but Mary was taken and imprisoned in a lonely castle on an island in Loch Leven. There she not only abdicated from the throne, allowing her 12-month-old son to become James VI of Scotland (later James I of England), but miscarried twins.

The birth remained a secret until Mary herself recorded the episode in her memoirs years later. The maturity and sex of the foetuses is unknown, but as the recognition of twins in the products of conception is unlikely before 12 weeks, they were probably conceived after Darnley's death and before her marriage to Bothwell.

As there are no contemporary accounts of her pregnancy, it seems Mary either concealed it or the whole episode may have been a figment of her imagination. If they had survived, the elder (if a boy) would have had no claim to the Scottish throne as baby James had already been crowned king. In passing, as we have seen, James's father's family name was Stewart, and when he became James I of England he started the Stewart Dynasty which was later to include such luminaries as Charles I who was beheaded after the English Civil War and Charles II, that well-known womaniser.

If any of Queen Anne's great brood of children had survived into adulthood and had inherited the throne the Stewart dynasty would have continued; her great great grandmother was Mary Queen of Scots. As it was, Anne became the last of the line and the crown went to a George I from Hanover, a distant cousin who could not speak a word of English. Similarly, the Victorian era would have been called something else if Adelaide had come good with her twins.

But in her well-ordered life, Princess Mary of Denmark will, I am sure, have no such dramas and I know we all wish her and her family well.