15weeks pregnant. OBGYN said cervix length 2.4cm. Maternalfetal expert said it is too early to check cervix length. What if it worsens before next apptmt?

Cervical shortening. The average cervix at 15 weeks is usually 3 cm or more, but what's more important is whether or not there was funneling. When the tech pushes on the uterus and the membranes and cervix appear to flatten out or even bulge through the cervix then you have funneling. If that happens they likely discuss using a pessary or elective cerclage. Prior preterm birth patients do get the length check early.