"My baby is 9 years old today, and more then ever we realize how precious every day is," Spears captioned the photo. "So, we have to thank these 2 HEROES John and Victoria are the first responders, who literally saved Maddie's life, and they were able to celebrate her another year of her life with us this past weekend! Thank God for these amazing people, and thank you God for your amazing grace. We are so blessed today, and everyday with this little angel! HAPPY BIRTHDAY MADDIE."