Progesterone and Aminophylline for the Prevention of Preterm Labour

The aim of this study is to investigate whether the combination of aminophylline and Progesterone (P4) is acceptable to women at high-risk of Pre-term labour (PTL). If this proves to be the case, a larger double blind, randomised controlled trial will be conducted to test the hypothesis that the combination of P4 and aminophylline reduces the risk of PTL more effectively than P4 alone. The study is a randomised study where participants will be either administered a combination of aminophylline and Progesterone (P4) or Progesterone (P4) alone.As the study is open label, the participants and the study doctor will know which study medications the participant is taking at all times during the study.