I read with great interest the recent Society for Maternal-Fetal Medicine Clinical Guideline concerning progesterone treatment to prevent preterm birth.

I applaud the Society for Maternal Fetal Medicine’s Publications Committee and Dr Berghella’s efforts to apply evidence-based medicine to clinical practice and to provide perspective about the sometimes contradictory results of a number of clinical trials of progesterone therapy.

In describing the National Institute of Child Health and Human Development Maternal-Fetal Medicine Unit Network trial, on page 380, the phrase “compounded 17P” is used. This may suggest to the reader that the drug that was used in this trial was supplied by a compounding pharmacy. This was not the case. The 17P drug that was used was manufactured by a research pharmacy using the US Food and Drug Administration’s Good Manufacturing Practices. We hope this information eliminates confusion regarding the drug that was used.