An Australian woman birthed a 13-pound baby. What are the health risks?

Natasha Corrigan is making international headlines after giving birth to a 13-pound, 4-ounce baby—or a "fat little man," as she called him.

Brian Liddle Jr. is one of the biggest babies ever born in Australia, and is twice the average birthweight. Corrigan gave birth to Brian after seven hours of a natural labor, which she said extra staff members had to help with due to the baby's size.

Corrigan isn't the first person to give birth to a larger-than-average baby:

* The biggest baby ever was born 22 pounds in Ohio, according to the Guinness World Records. Sadly, the boy, named "Babe," died 11 hours later.

* Last year, a Perth, Australia, woman gave birth to a 13-pound baby through cesarean section.

* Just weeks after, an Indian woman had a 15-pound baby girl, also via a c-section.

There has been a 15 to 25% increase in babies weighing 8 pounds and 13 ounces or more in the past two to three decades in developed countries, according to 2013 report from medical journal The Lancet.Those babies and their mothers face some additional risks.

Though the average birthweight is 7 pounds and 11 ounces and more than 10 pounds is considered fairly large, "What the right size is for any mom or baby is quite a big range," according to Dr. Hyagriv Simhan, director of maternal-fetal medicine at Magee-Women's Hospital at the University of Pittsburgh Medical Center.

There are certain health conditions, such as diabetes, or gestational diabetes—which develops during pregnancy—that predispose women to having babies over 10 pounds, Simhan said. A baby that weighs more than 10 pounds poses the risk of delivery complications such as excessive bleeding for the mother, increasing the likelihood of long-term nerve injuries or needing a c-section. Even then, the risk of bleeding and delivery complications loom.

Long-term health complications to the baby include obesity in childhood and potentially beyond, he said

How some babies get so big

Multiple factors contribute to large birthweight, including diabetes or family history. A woman who is 6-foot-2 and 180 pounds is more likely to have a larger baby than a 5-foot-3 woman who weighs 100 pounds, Simhan said, adding that physicians attempt to predict birthweight using traditional methods such as ultrasounds and physical exams.

"We have to use these inaccurate methods of gauging size," he said. "In women who are undergoing labor, if we think a baby is larger than average, we'll definitely follow the labor," and potentially suggest a c-section if progress is slow or stalled.

The c-section delivery rate in the U.S. declined for the third year in a row to 32% of births in 2015, the lowest rate since 2007, according to the Centers for Disease Control. More than 2.7 million babies in the U.S. were delivered through vaginal birth in 2015.

Additional risks posed by larger babies

Immediate risks of a large birthweight for the mother are delivery complications such as vaginal and rectal laceration or postpartum hemorrhage, according to Dr. Clark Nugent, a professor of gynecology and obstetrics at the University of Michigan. Long-term risks include high risk of pelvic floor disorders or prolapse, he added.

For the baby, there's also a higher risk of shoulder dystocia, or when the baby's head delivers but the shoulders don't, and oxygen takes too long to deliver.

"Any time that someone is delivering a baby, we have to be prepared for shoulder dystocia," Nugent said.

Other potential health complications include low blood sugar or an elevated blood count, which could lead to the baby being admitted to a neonatal all-intensive nursery.

Women remain in the hospital after delivering a baby with a large birthweight via c-section for 3-4 days should there be no complications, which is standard, Simhan said. Recovery time after vaginal deliveries depends on complications, including tears or injuries, which are more common with large babies.

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