"The both of us were very, very uncomfortable," she said.
Buckley said that by 38 weeks, her doctor saw no reason to make her continue to wait. So on March 12, the 31-year-old from Corning, New York, went to deliver the baby through a planned C-section, she said.
She said it took two doctors at Arnot Ogden Medical Centre - one pushing down on Buckley and one pulling Harper out from under her ribs - to bring the 15-pound, 5-ounce (7kg) girl into the world.
"I was in awe," Buckley said of the moment she and her husband, Norman, saw their newborn daughter for the first time. "Yes, she was big, but she was entirely perfect to me."
In fact, Harper was twice the size of most newborns. Buckley admitted that the morning after she gave birth, "I felt like I had been hit by two tractor-trailers simultaneously."
Norman and Joy Buckley married in 2008 and, soon after, tried to get pregnant. It didn't happen.
Buckley said she was diagnosed with polycystic ovarian syndrome - a hormonal disorder that makes it harder for women to get pregnant and carry a baby - and was told she had about a 15 per cent chance to conceive naturally. She said she also has Type 2 diabetes.
The couple decided to become foster parents to a newborn baby, Heaven, and several years later adopted her.
Then the couple got a surprise.
In 2016, Buckley said, she took a pregnancy test because she had not been feeling well. Their son, Chase, was born on December 12, 2016 - at 5kg, the mother said.
Buckley said she could not believe it when she learned in summer 2017 that she was pregnant with another "miracle baby."
But the delivery would be rough.
When doctors were performing the C-section, Buckley said, her husband almost fainted - not because he was squeamish but because he was so worried about her.
"It was a pretty violent thing to watch," she said.
Buckley said she felt as though she had been beaten up and her newborn "had bruises all over her body from being pulled out."
Harper is still in the newborn intensive care unit at the hospital, but Buckley said she hopes to be able to take her home soon.
Regan Theiler, chair of the Division of Obstetrics at the Mayo Clinic in Rochester, said it is "really unusual" to see babies born that large, explaining that the average is between 5.5 and 7.5 pounds (2.5 and 3.5kg).
According to the Mayo Clinic, when babies are born weighing above average, the condition is called "fetal macrosomia," which describes about 9 per cent of babies born worldwide.
It states:
"Fetal macrosomia can be caused by genetic factors as well as maternal conditions, such as obesity or diabetes. Rarely, a baby might have a medical condition that speeds fetal growth.
"In some cases, what causes a larger than average birth weight remains unexplained."
Theiler, an obstetrician-gynecologist, said macrosomia is most commonly seen in women with diabetes. She said the condition seems to be related to the high level of insulin in the mother, "which acts like a growth factor," and can make the baby grow larger than normal.
Theiler said that although the condition can result in negative outcomes, "the long-term outcomes are very good for these babies" if there is no trauma during childbirth.
Officials from the New York Health Department told the New York Post that they are investigating to determine whether the newborn, who was born with the weight of an average 5-month-old, may be the largest baby born in the state.
But, Buckley said, that's not what matters.
"I don't care about the state record. I don't care about the news articles," she said. "I care that I was given the opportunity to become a mum again."
