Thirty-one years ago, it was the same spectacle outside St. Mary's Hospital in London -- hordes of media and onlookers camped out waiting for the arrival of the newest royal heir.
Since that time, when Prince William was born, we've mapped the human genome, cloned a sheep and created a vaccine to protect against chickenpox. We can program our 3-D televisions with our smartphones.
But as for our skill at predicting the arrival of the royal baby -- reportedly due on Saturday for Prince William's wife Kate, the Duchess of Cambridge?
"If you're taking an office pool and trying to pick a day, we are as bad at that now as we were 30 years ago," said Hyagriv Simhan, chief of maternal fetal medicine and vice chair of obstetrics at Magee-Womens Hospital of UPMC.
That said, doctors are generally much more sure these days than they were a generation ago about the timing of a woman's 40-week due date.
Pregnancy is still dated, as it has been for decades if not centuries, primarily by the date of the mother's last menstrual period, said Eugene Scioscia, vice chair of obstetrics and gynecology for the West Penn Allegheny Health System.
The biggest change in the field has been ultrasound technology, which was just getting started in pregnancy use in the early 1980s.
Using ultrasounds, pregnancy can be dated much more accurately. And the earlier the ultrasound, the more accurate the date. The advent of first-trimester genetic testing, which has become popular in the past decade, has pushed ultrasounds earlier and earlier, said Dr. Scioscia, meaning that women have a better sense of their due dates than they did even a decade ago.
Home pregnancy tests have helped, too, he said, because women are aware of their pregnancies closer to the date of their last menstrual period.
"The diagnostic ability to date someone has changed drastically," he said. "We can really narrow someone's due date in terms of accuracy quite well."
But even if the due date is known to the minute, that doesn't mean that a baby will come out on time. "It happens when it's going to happen," said Dr. Simhan. For the majority of women, he said, that day is between 38 and 40 weeks.
A study from 2002 found that 52 percent of spontaneous births -- those that did not involve cesarean sections or inductions -- took place between weeks 37 and 39. Thirty-six percent of births happened in the two weeks after a woman's due date, with just 6 percent occurring after 42 weeks.
After 42 weeks, the chance of stillbirth increases substantially, Dr. Simhann said. Decades ago, women were allowed to go beyond 42 weeks more frequently, because the dating of the pregnancy was much more of a guessing game.
With due dates now known precisely, what makes one baby stay snugly in the womb while others bust out ahead of schedule?
"Should I be able to answer that question, I would receive the next Nobel Prize in medicine," Dr. Scioscia said. "It's been studied ad nauseam and we don't know."
It isn't just idle curiosity resting on when the duchess will birth the next heir to the throne.
Baby betting has become a big industry in England, with bets taken on everything from the due date to the baby name (favorites are Alexandra for a girl and James for a boy) to the color of Kate's sister Pippa Middleton's dress on her first visit to meet the baby (white/cream leading at 4-1 odds).
There are now 2-1 odds that the baby will arrive in the last week of July, according to the Paddy Power bookmaker.
When the royal heir does make his or her presence known, the first communication with the public will likely be with an official notice on a glass-fronted easel at Buckingham Palace. Depending on the time of day, a 41-gun salute will then take place in Hyde Park.
And then -- and only then -- will the Palace begin to announce the birth via Twitter -- yet another advance since the last royal baby watch outside St. Mary's Hospital.
Anya Sostek: firstname.lastname@example.org or 412-263-1308. First Published July 11, 2013 4:00 AM