What methods do not work to prevent preterm labor?

Researchers have found that some methods for trying to stop preterm labor are not as effective as once thought. These include:

Home uterine monitors¹
Routine screening of all asymptomatic women for bacterial vaginosis (Trichomonas vaginalis) infection.² Routine screening and treatment with antibiotics did not reduce preterm birth; in fact, the latter increased the risk of preterm birth.²

Citations

Iams, J. D., Newman, R. B., Thom, E. A., Goldenberg, R. L., Mueller-Heubach, E., Moawad, A., et al. (2002). Frequency of uterine contractions and the risk of spontaneous preterm delivery. New England Journal of Medicine, 346, 250–255.
Carey, J. C., Klebanoff, M. A., Hauth, J. C., Hillier, S. L., Thom, E. A., Ernest, J. M., et al. (2000). Metronidazole to prevent preterm delivery in pregnant women with asymptomatic bacterial vaginosis.New England Journal of Medicine, 342, 534–540.