Last Week I Was Told That My Baby Had Enlarged

Last week I was told that my baby had enlarged lateral ventricles at 24 weeks, measurement was 9.91 mm (left). All other measurements indicates a normal baby according to my ultrasound results. The doctor said that an ultrasound should be done after 2 weeks to see the evolution of this measurement. She also said that in most cases this measurement decreased. What it is to be done if it will increase? Is it an amniocentesis necessary?