Just found out my baby is underweight.

I'm 37 weeks and 3 days. First Child. And The doctor told me she is 
5 pounds, 15 ounces. And that her head is quite small. But nothing is wrong with her. I am a slim/tiny person that could also be it. I hope n pray everything goes well🙏 Has Anyone Had A 5 pound baby at 9months? And or a c-section. ?