The Boy Who Gave Birth to His Twin

Martin Brookes

December 2003

It must be quite something to discover you've been walking around all your life with your twin inside you. This is what happened to Alamjan Nematilaev, a seven-year-old boy from Kazakhstan. A strange feeling no doubt. Can we really think of Alamjan's twin as just that, a twin? Technically the answer is yes. A foetus in foetu, or baby within a baby, is a developmental hiccup that happens very rarely to identical twins. But the mistake comes so early in development that the twin inside never really had any chance of being a real live twin. Here we take a look at the pitfalls of embryonic development and reveal just what a rocky road it can be.

The boy who gave birth to his twin | Embryonic puzzle | Control genes | Fraught business | Find out more

We know how difficult it can be travelling around sometimes: traffic, roadworks and a million other inconveniences often obstruct our smooth passage from A to B. But the next time you're stuck in a logjam on the M25, remember that you've already made it down the most difficult road of all. It was the first journey of your life, and it puts the worst bank holiday traffic in the shade.

The journey from egg to embryo is the most perilous trip that any of us will ever have to endure. The majority of human embryos never make it; they are lost along the way to an obstacle course of developmental wrong turns and genetic blunders. Only a lucky few survive to face the tight squeeze into the outside world.

The great journey

We all start life as a fertilised egg; a single cell tumbling down the oviduct of our mother. Heading down towards the uterus, the cell begins to divide and multiply. One cell becomes two cells, two cells become four, four become eight and so on. By the time it reaches the uterus, the nascent embryo is already a hundred cells strong. As it prepares for implantation into the uterus lining, the embryo's cells start to assume regional identities, organising themselves into layers of distinctive tissue. Already, the ground plan of placenta, skin and bone is taking shape.

As the embryo continues to grow, the sheets of tissue curl over at their edges, eventually joining up to form a cylinder of cells. The hollow tube at its centre is destined to become the baby's gut. By four weeks the embryo has a distinct head and tail, a heart and a basic nervous system. Everywhere, cells are diversifying into the disparate tissues that make up the body – blood, skin, muscles, nerves and bone. Some cells even commit suicide, dissolving away to bring limbs, fingers and toes into sharp relief. By eight weeks, the embryo resembles the form of a human being.

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