Understanding Contraction-Stopping Medications During Pregnancy

Question
My sister-in-law went to the hospital three early to her due date and her contractions were 5 minutes apart her cervix was still thick and they said it was to early. So her doctor gave her a shot in her arm. She would like to know exactly what is in this "shot", and will it make her pregnancy be longer?

Answer
Usually, we use Terbutaline to stop preterm labor. Terbutaline is given as a subcutaneous injection and will stop any contractions a woman may have. It will not prolong the pregnancy and, hopefully, will allow the pregnancy to continue until the due date. Somtimes, if the contractions do not stop, we continue to give the terbutaline orally at home. HOwever, if the contractions stopped with the inuection, nothing else need be done.