**4.1. Dichorionic pregnancies**

Finberg et al. [46] suggested repeat scans every 4–6 weeks for noncomplicated dichorionic pregnancies. However, in current daily medical routine, surveillance is closer: follow-up ultrasound assessments are performed every 3–4 weeks [4, 47]. But, if a complication is suspected, and more specifically when CRL, estimated fetal weight or amniotic fluid volume are different between the two fetuses, routine scans have to be repeated every 2 weeks, or within a week [48].
