###Human: What could the possible cause of miscarriage at 5th week? ###Assistant: Hello.  First trimester miscarriages are very common, and mostly they are due to underlying abnormalities in the baby which are not diagnosed on ultrasound, and the most common cause is chromosomal abnormalities. So nothing to worry about and you can try for your next baby and keep taking folic acid meanwhile. I hope it has helped you. If you require any further queries, please do not hesitate to contact me.