Hi Rani Good morning,
Thanks for your question.
TIFFA scan is done for targeted imaging of fetal anomalies. Usually it is done at 18-20 weeks. Most of the major structural abnormalities can be picked up at this stage except for heart or cardiac defects. The best time to view a babies heart is at 24 weeks of gestation.
I don't think you should be so worried at present. You have two choices; you may wait for 4 weeks & go for a repeat scan at 24 weeks or you may go for a tertiary level scan from a specialist sonologist in your area. If the report is still not certain other options are fetal echocardiography
or perhaps doppler ultrasound
Best of luck.