Can A Low Sperm Count Cause Miscarriage?

My daughter has had 4 miscarriages and each time been told after the scan the sac had been formed but no baby inside. Her partner has taken Epilim for over 20years and I am wondering if it is possible he could be infertile?They have had genetic tests and been told that everything is ok and healthy. However his sperm has not been tested. She has just found out she is 5 weeks pregnant and scared the scan will reveal the same results as previous> what else can they do?