Weighing in at just 8.6 ounces (241 grammes), Saybie is believed to be the smallest baby ever to survive a premature birth.

Sharp HealthCare in the United States announced on May 29, 2019, that the infant girl was delivered by Caesarean section in December 2018 at just 23 weeks gestation after her mother suffered from pre-eclampsia – a life-threatening condition that causes very high blood pressure.

Although the infant was not identified by her real name due to her parents’ desire for privacy – Saybie is the nickname given by her medical team – Sharp said that after searching worldwide, it could find no lighter baby.

In April 2019, the world’s smallest surviving baby boy Ryusuke was allowed to go home three months after he was born weighing 9.1oz (258g).

Sharp Mary Birch Hospital for Women and Children neonatologist Dr Paul Wozniak explained that with babies this small, the first hurdle is simply making sure they get a chance to breathe.

Underdeveloped lungs mean they all need help, so placement of an extra-small breathing tube is essential, but such a delicate procedure often fails over and over again before a precise pair of hands is able to coax the device through the airway to the lungs.

Sometimes, intubation on tiny airways simply fails, contributing to a very high mortality rate among those born too early, he said.

But for Saybie, the tube went in on the first shot. Given that she was a full 100g smaller than the smallest baby he had ever tried to intubate and that it was necessary to cut down the smallest breathing tube that the hospital had in inventory, Dr Wozniak said feeling that instrument slide into place on the first try verged on the religious.

“When it went right in, oh, my God, it was instant relief,” he said.

Having a breathing tube in place so quickly allowed quick delivery of surfactant, a chemical that prevents the tightly-packed air sacs in a premature baby’s lungs from sticking together.

Use of this chemical is widely credited with significantly reducing the amount of respiratory distress in premature infants, especially in so-called micro-preemies born before 28 weeks.

As the largest maternity hospital in California, Mary Birch is used to handling plenty of premature babies and many are quite small.

But Saybie’s size – only nine inches (2.54 centimetres) long at birth – required adjustments for the hospital’s level three neonatal intensive care unit (NICU).

Special blood pressure cuffs were necessary, as were particularly microscopic diapers.

At just 245g, the scales built into standard NICU beds were thrown for a loop.

“Our beds can’t weigh anything that’s less than 300g, so we had to take her out and weigh her on the old-fashioned scale,” Dr Wozniak said.

Anyone who has had a premature baby in a NICU knows that every ounce of weight gain is cause for celebration.

It took Saybie about a month to hit the one-pound (453g) mark and a bit longer before her breathing tube could be removed.

At first, she received just a single millilitre of breast milk through her feeding tube at a time.

Premature babies are also more susceptible to infection than full-term babies because they spend less time connected to their mother’s blood supply, providing less chance to receive protective antibodies circulating in mom’s blood.

Though Staphylococcus infections are common in micro-preemies, Dr Wozniak said Saybie managed to avoid infection throughout her stay.

She also managed to stop receiving oxygen before going home and was able to feed on her own for a full month before leaving the hospital.

All of these items, Dr Wozniak said, were quite remarkable.

“Some babies we’ve had in here nine months to a year before they can go home,” he said. “To me, it’s remarkable she didn’t go home on oxygen, because most babies this small will, or with a feeding tube.”

According to a 2015 study, micro-preemies suffer particularly high mortality rates of 30% to 50%, and severe complications are so common that neonatologists keep a special card on them to refer to when talking about the odds with parents.

“For significant bleeding of the brain, that occurs in 35%, and chronic lung disease we see in about 47% of these babies,” Dr Wozniak said.

Why was this particular child able to defy such difficult odds so consistently?

The neonatologist said it’s a combination of factors. “It’s good genetics and that’s combined with good luck.”

Now five months old, Saybie weighed five pounds and six ounces (2.44kg) and was double her birth length at 16” (41cm) when she went home in early June 2019. – The San Diego Union-Tribune/Tribune News Service