Femurs Measuring Behind

Does anyone know anything about the femurs measuring 2 weeks behind and the rest measuring 2 weeks ahead? I'm 32 weeks today and I get monthly growth scan for hypertension. His femurs have consistantly been measuring 1-2 weeks behind since my 20 week scan and the rest has been measuring ahead. I've been told all of the ultrasounds have been normal and I have an appointment tomorrow to discuss this month's scan. But I mistakenly googled it this time and kept seeing soft markers for downs. Should i be concerned?