A mum and dad are celebrating the arrival of their ‘hidden twin’ who had odds of just 1 in 30,000 of being born.

Sadie Brittle, from Polesworth, Warwickshire, experienced a potentially life threatening ectopic pregnancy, where a fertilised egg implants itself outside of the womb, typically in the fallopian tubes.

While that fertilised egg had to be removed, internal bleeding masked the fact that the baby’s twin, Teddie, had implanted normally in her womb and was still alive. This is known as a heterotopic pregnancy.

“I wondered why my stomach was still so swollen,” Sadie told the BBC, “and that’s when we found out that he was the hidden twin.”

Teddie was born at George Eliot Hospital in Nuneaton, weighing 6 lbs 10 oz (3kg).

“I just can’t believe that he’s here and he’s okay,” Sadie added.

Heterotopic pregnancies

A heterotopic pregnancy is a condition where one foetus has implanted outside the uterus (usually in a fallopian tube), while the other is in the uterus. As this second foetus is not always discovered straightaway, it is often referred to as the hidden twin.

The condition is most common in couples who has conceived with medical assistance, such as in vitro fertilization (IVF). According to recent information the rates could be around 1 in 7,000 pregnancies, or 1 in 900 where ovulation in medically induced.

However, in natural conceptions the odd of a heterotopic pregnancy is just 1 in 30,000.

Some studies have found that heterotopic pregnancies can carry an increased risk of miscarriage of the second twin developing in the womb, but around 67% of women are able to carry the baby to term following treatment.