Definitions of the levels of evidence (I, II-1, II-2, II-3, and III) and grades of recommendations (A-E and I) are provided at the end of the "Major Recommendations" field.
- Women at risk for preterm labour (PTL) should be encouraged to participate in studies on the role of progesterone in reducing the risks of preterm labour. (I-A)
- Women should be informed about the lack of available data for many neonatal outcome variables and about the lack of comparative data on dosing and route of administration. Women with short cervix should be informed of the single large randomized controlled trial (RCT) showing the benefit of progesterone in preventing PTL. (I-A)
- Women and their caregivers should be aware that a previous preterm labour and/or short cervix (< 15 mm at 22 to 26 weeks' gestation) on transvaginal ultrasound could be used as an indication for prophylactic progesterone therapy. The therapy should be started after 20 weeks' gestation and stopped when the risk of prematurity is low. (I-A)
- On the basis of the data from the RCTs and meta-analysis, it is recommended that in cases where the clinician and the patient have opted for the use of progesterone the following dosages should be used:
- For prevention of PTL in women with history of previous PTL: 17 alpha-hydroxyprogesterone 250 mg intramuscularly (IM) weekly (I-B) or progesterone 100 mg daily vaginally. (I-A)
- For prevention of PTL in women with short cervix of <15 mm detected on transvaginal ultrasound at 22 to 26 weeks: progesterone 200 mg daily vaginally. (I-A)
Definitions:
Quality of Evidence Assessment*
I: Evidence obtained from at least one properly randomized controlled trial
II-1: Evidence from well-designed controlled trials without randomization
II-2: Evidence from well-designed cohort (prospective or retrospective) or case-control studies, preferably from more than one centre or research group
II-3: Evidence obtained from comparisons between times or places with or without the intervention. Dramatic results in uncontrolled experiments (such as the results of treatment with penicillin in the 1940s) could also be included in this category
III: Opinions of respected authorities, based on clinical experience, descriptive studies, or reports of expert committees
Classification of Recommendations**
A. There is good evidence to recommend the clinical preventive action.
B. There is fair evidence to recommend the clinical preventive action.
C. The existing evidence is conflicting and does not allow to make a recommendation for or against use of the clinical preventive action; however, other factors may influence decision-making.
D. There is fair evidence to recommend against the clinical preventive action.
E. There is good evidence to recommend against the clinical preventive action.
I. There is insufficient evidence (in quantity or quality) to make a recommendation; however, other factors may influence decision-making.
*The quality of evidence reported in these guidelines has been adapted from The Evaluation of Evidence criteria described in the Canadian Task Force on Preventive Health Care.
**Recommendations included in these guidelines have been adapted from the Classification of Recommendations criteria described in the Canadian Task Force on Preventive Health Care
