WHEN Prince George's little brother or sister arrives in April (or May, if the Duchess of Cambridge ends up going overdue), she or he is likely to be born in St Mary's Hospital, London, with Wills looking on, before a bit of "skin-to-skin" bonding with Kate.

No doubt the Duchess is dusting off the birthing plan she drew up before having George, in which she'll have stated her preferences on everything from the use of birthing pools and gas and air, to delayed cord clamping and even what kind of music she wanted in her room.

Like everything these days, childbirth in 21st Century Britain is about choice. A recent BBC documentary, Childbirth: All Or Nothing - now available on iPlayer - follows four thirtysomethings, who cover the entire spectrum from home birth to full medical intervention and everything in between. But just how has childbirth evolved?

FULL CIRCLE

Over the centuries, we've gone from women giving birth in their private bedchambers, to a medicalised approach designed to limit maternal deaths - and now, back to a trend for home births, with just a midwife present.

Between 2009 and 2012, the maternal death rate in the UK was 10 in 100,000 women. In 1900s America (where this data appears more accessible), the death rate was 850 per 100,000.

In the century in between, medical advances, such as monitoring babies' heart rates and the advent of antibiotics, have succeeded in saving more lives. In recent years, the use of medical interventions has increased, with more women having elective caesareans (13.2% between 2013-14) and inductions (25 per cent).

KEEP OUT, MEN

In 1533, King Henry VIII's second wife Anne Boleyn disappeared into her private chambers for a month with her closest female attendants, as the Science Museum's excellent History Of Medicine website reveals in its interactive section on childbirth (www.sciencemuseum.org.uk). No dads were allowed.

But alcohol was. Women drank posset, an eggnog-like mixture of cream or milk and alcohol, to nourish and soothe the pain.

PAIN RELIEF

By 1857, when Queen Victoria was giving birth to Princess Beatrice, her ninth and last child, chloroform had become the drug of choice. But it could be fatal in strong doses, so her anaesthetist, Dr John Snow, kept a careful check. Even so, Victoria apparently passed out...

Men were allowed to be in the room, leading the charge for a more clinical version of childbirth - Victoria's husband Albert was so hands-on, he administered her first two doses of chloroform.

It was also custom for mothers to share a warm spiced wine drink, caudle, with the women who'd helped them give birth, though that declined when doctors said it made mothers more prone to infection - nowadays, women are advised not to drink alcohol while pregnant or breastfeeding.

By 1948, when the soon-to-be Queen Elizabeth II was in labour with Prince Charles at Buckingham Palace, laughing gas (nitrous oxide) had become the drug du jour, preceding epidurals. Penicillin meant fewer women died of infection and doctors were more willing to do caesarean-sections, which were considered risky.

INTERVENTION

Foetal monitoring began in the 1820s, as doctors used a stethoscope to listen to baby's heart in the womb. By the 1960s, specialised monitors meant a continuous printout of baby's vital signs was possible, but such monitoring was controversial, as some argued it meant the mother was tethered to the device.

Forceps, originally a secret invention by the Chamberlen family of male midwives, had become popular, with - by the 1850s - doctors modifying them to make them more comfortable.

BACK TO BASICS

In 1933, Suffolk-born obstetrician Grantly Dick-Read advocated a return to more simple methods in his first book, Natural Childbirth. His ideas were ridiculed by the establishment, but his second book, Childbirth Without Fear (1942), became an international bestseller.

Across the pond, midwives such as Ina May Gaskin were promoting similar concepts, such as birthing centres, water birth, and home birth as alternatives to the high-tech hospital model.

Dick-Read became the first president of the National Childbirth Trust (NCT) charity, which was set up in 1956 and advocates a more natural approach.

Ultimately, whether mums-to-be choose to give birth at home or hospital, the goal is still the same: for mother and baby to be safe and well.