Girls, I went for an ultrasound today. We could see normally, but they…

Girls, I went for an ultrasound today. We could see normally, but they directed me for a pelvic ultrasound. They said it's a gestational pregnancy (they calmed me down). The baby is growing, there's heartbeat. But there's one thing. I'm very upset ? because of what I was afraid of. They said there's a threat, I need to be treated ? How scary is this? What can cause it? And what further actions should I take?! Please tell me ??