It can be concerning if no gestational sac is seen on ultrasound in the 6th week of pregnancy, especially with a low beta hCG level like However, there are several factors to consider before jumping to conclusions. It's possible that the pregnancy is still at an early stage and the gestational sac has not yet developed or may be too small to detect. Additionally, incorrect dating or positioning during the ultrasound could also contribute to not seeing the sac. To get a clearer picture, your doctor may recommend repeating the ultrasound after a few days or weeks to monitor any changes in the development of the gestational sac and embryo. In some cases, this could indicate a potential miscarriage or ectopic pregnancy, but further evaluation is necessary before reaching any definitive conclusions. It's important to consult with your healthcare provider who can provide personalized guidance based on your specific situation and medical history.