Fetal ultrasound show small head circumference and also small stomach?

Gestational age ?: Depends what gestational age/trimester you had study done, serial measurements will establish a pattern and let you know what is the next step, one measurement is not a diagnosis, especially if this first trimester. Should compare HC to weight and crown-rump length to get full picture on growth

Need more info: you must provide more details--how many ultrasounds were done, and at what gestational age, and who did the exams--an ultrasound tech or a perinatologist? And how small was it? Were parental head circumferences measured?--sometimes a parent will be affected with benign familial microcephaly.

Fetal ultrasound: Depending on several factors, including the experience of the sonographer, the fetal head and abdominal measurements can be on the "small" side. If your ob provider is not concerned, it is probably just because fetuses , just like older children, grow at different rates, and "catch up later".