I just had my first ultrasound my crl is measuring 7 weeks 6 days but the gs is measuring 5 weeks 6 days. the babies heart beat was 138bpm. everything ive read is that if the gs is more then 5 mm smaller pregnancy may not be viable mine is 9mm out?

By NIH website: the rate of fetal death was 80.0% when the gestational sac diameter-crown-rump length difference was less than 5 mm, 26.5% when the difference was 5-7.9 mm (P less than .002 compared with less than 5 mm), and 10.6% when the difference was 8 mm or more (P less than .0001 compared with less than 5 mm). Your fetus should be fine, take care and good luck with your pregnancy.