 These studies suggest that in singleton pregnancies with a previous history of preterm birth progesterone treatment may prevent the patients from having subsequent premature births. Nonetheless, the results of these series must not be generalized to all pregnancies at high risk. Additional studies to evaluate the use of progesterone ovules in multiple pregnancies are necessary, as these pregnancies are increasing due to the advanced maternal age at the conception time and also due to the widespread use of assisted reproductive techniques. 