NEWNAN, Ga. -- A rare set of quadruplets has turned four months old!

11Alive first introduced you to the Miller quadruplets – three boys and one girl – shortly after their birth in December. Their delivery was special because the quadruplets were conceived naturally – without the use of any fertility drugs – something so rare that the odds are only one in 700,000. Their delivery was a first for Piedmont Newnan Hospital.

On Tuesday, Piedmont Newnan Hospital shared photos of the quartet, who are happy, healthy and growing just fine.

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PHOTOS | The Miller Quadruplets through the years

The infants turned 4-months-old on Sunday and returned to the hospital Tuesday afternoon to for a checkup with their mom Kourtney's OB, Dr. Heather Turner, and NICU staff. All of the babies weigh about 9 lbs each and are developing their own personalities, the hospital said. It's a vast improvement from when the four were delivered at about 30 weeks and weighed only three pounds.

11Alive’s Kaitlyn Ross was with the family when they were cleared to go home from the hospital in February. The Millers said it was a relief to finally have them all home. But four new babies means big adjustments for the family.

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Mom Koutney said everything with four takes a little more time – from clothing them, to feeding them, even to naming them. For the first few months, they were known as babies A, B, C and D when they were born. Kourtney said coming up with four names wasn't easy. But now, Bryant, Brandon, Braydon and Kenlee are all settling in nicely.

PHOTOS | Medical team delivers quadruplets at Piedmont