Nausea drugs for morning sickness

I am concerned about the long term effects of ondansetron on the fetus.  It was prescribed for my daughter (4 1/2 weeks pregnant).  She took the drug for 2 days and the results were surprisingly marginal, considering that this drug is used for cancer patients undergoing chemo/radiation treatment.  It is my understanding that the drug thalidimide has been reintroduced in some cancer medications because of its growth inhibiting properties. That drug was at one time considered safe.  Do we really know what the long-term effects are of powerful drugs like ondansetron given in the first trimester?  This was the drug prescribed after my daughter called the doctor's office asking what she could do to relieve her morning sickness symptoms.  What safe alternatives are there to powerful drugs that could potentially cause health problems when these babies become adults. I look forward to comments.  Thanks.