Gender result error

Meron po bang ngkamali ng Gender result during Utz here? 2nd pregnancy ko and I'm carrying twins, 2 boys ang result, Boy n na din un panganay ko.. medyo skeptic lng aq kc d nman ma point nun ng ultrasound un gender in Twin A at Twin B... mura lng un procedure, Php760 sa twins.. samantalang sa Commonwealth Hospital (near SM Fairview) nasa Php3,600 nun 13 weeks to know the hearbeat.. Gaano ka taas kaya ang reliability nun...