Scared of another CHD

Third baby. the first two were born with a congenital heart defect. My first child had to have heart surgery at five days old. It was a very serious condition with a .003 chance of survival. she's now 3 and wonderful! my second child hand a regular heartbeat. not very concerning, except for my first child was so serious that they monitored very closely/carefully. really scared me! I'm 19 weeks and go for my first ultrasound soon and I'm very nervous!