What is the safest oral drug to slow or stop contractions?

Depends on patient. The drug(s) chosen to stop preterm labor all have benefits and all have side effects. A drug may work in some patients and not in others. Some patients may need higher doses than others. Pre-existing medical conditions may not allow certain patients to use some drugs. An perinatologist (specialist in treating such problems) or an experienced ob-gyn doctor can help a patient decide on a plan.