Meghan's pregnancy technically classed as 'geriatric pregnancy'

Meghan, Duchess of Sussex is expecting her first child at age 37. Photo / AP

Meghan, Duchess of Sussex, and Prince Harry today revealed they are expecting their first royal baby next spring.

Because of her age, the 37-year-old is technically classed as having a "geriatric pregnancy".

The term has been around for decades to describe a pregnant woman over the age of 35 - but is not widely used any more because of its "insulting" tone.

Meghan is in "good health" and has already had a successful 12 week scan - meaning the child was conceived towards the end of July and start of August.

The former Suits actress, who is in Sydney for the start of a three-week tour of New Zealand, Australia and the Pacific Islands, is one of thousands of women to have delayed their pregnancy.

The Queen, who today congratulated the couple on their news, was also 37 when she gave birth to her fourth child, Prince Edward, in 1964.

Sophie, Countess of Wessex, was 38 when she gave birth to Lady Louise in 2003 and 42 when James, Viscount Severn, was delivered four years later.

NHS figures released last year showed the number of women over 40 giving birth in England and Wales has tripled since the 1980s.

The data revealed 14.7 per 1000 had a child after turning 40 in 2014 - drastically up from the 4.9 per 1000 recorded in 1984.

Delayed pregnancies are usually made by career-focused women who have instead decided to focus on establishing themselves a high-flying job.

Female fertility begins to sharply decline after age 35 - the age technically classed as being a geriatric pregnancy.

However, the term has gone out of fashion and has been replaced by other names, such as "older mothers" and being of an "advanced maternal age".

Parenting blogs slam the term - which has been used for decades - as being "atrocious" and "insulting".

The Royal College of Gynaecologists and Obstetricians defines the "optimum period for childbearing" as being between 20 and 35.

In a position statement nearly a decade old, the body said it encourages women to "consider having families during the period of optimum fertility".

Women in their late 40s have as little as a one in 20 chance of becoming pregnant because of their lower supply of eggs, which are less capable of being fertilised.