Fetal Head Size Discrepancy in Late Pregnancy: Causes & Next Steps

Question
I am 24 years old. I am 36 weeks pregnant and had many sonograms and everything seemed perfect. I also had a 3-D sonogram at 28 weeks and she looked beautiful. I also had  the 5 month scan and everything was normal. Today I had a sonogram to determine the weight of the baby and she was approx. 5lbs. 9oz. The doctor said the head measured 2 weeks behind. I now have to go for another sonogram tomorrow. How could something happen now? I'm scared! Please answer my question.
Thanking you in advance

Answer
Everything may be perfectly normal. Don't worry. Sometimes, a sonogram will have a lag of the size of the baby and its gestational age. Sometimes, there can be Intrauterine growth restriction for various reasons. If all appeared to be progressing well, there is no reason to worry. Just see what the next sonogram shows. Usually, at 36  weeks gestation, it is normal for the estimated fetal weight  to be between 5-6lbs. Just be patient.