Tocolysis in the management of preterm prelabor rupture of membranes at 22–33 weeks of gestation: study protocol for a multicenter, double-blind, randomized controlled trial comparing nifedipine with placebo (TOCOPROM)
Authors: Lorthe Elsa , Kayem Gilles ,   on behalf of the TOCOPROM Study Group and the GROG (Groupe de Recherche en Obstétrique et Gynécologie), Kayem Gilles , Lorthe Elsa , Ancel Pierre-Yves , Abdoul Hendy , Briand Nelly , Lehmann Blandine , Cabanne Clémence , Marret Stéphane , Foix l’Hélias Laurence , Goffinet François , Schmitz Thomas , Charlier Caroline , Autret Fanny , Azria Elie , Balitalike Jadot , Billiemaz Kareen , Bohec Caroline , Bolot Pascal , Bornes Marie , Bouchghoul Hanane , Bourennane Malek , Bretelle Florence , Carbillon Lionel , Castel Christine , Chauleur Céline , Corroenne Romain , Coste Karen , Datin-Dorrière Valérie , Desbriere Raoul , Desfrere Luc , Dreyfus Michel , Dommergues Marc , Durrmeyer Xavier , Favrais Géraldine , Flamant Cyril , Gallot Denis , Gries Julie , Haddad Bassam , Julé Laure , Laffaille Cécile , Lepercq Jacques , Letamendia Emmanuelle , de Marcillac Fanny , Miler Caroline , Morel Olivier , Norbert Karine , Perrotin Franck , Poncelet Christophe , Renesme Laurent , Roumegoux Claire , Rozenberg Patrick , Ruiz Mireille , Sentilhes Loïc , Sibiude Jeanne , Subtil Damien , Tillouche Nadia , Torchin Héloïse , Tosello Barthélémy , Verspyck Eric , Vivanti Alexandre , Winer Norbert 
Published: September 2021

Abstract
Background
Preterm prelabor rupture of membranes (PPROM) before 34 weeks of gestation complicates 1% of pregnancies and accounts for one-third of preterm births. International guidelines recommend expectant management, along with antenatal steroids before 34 weeks and antibiotics. Up-to-date evidence about the risks and benefits of administering tocolysis after PPROM, however, is lacking. In theory, reducing uterine contractility could delay delivery and reduce the risks of prematurity and its adverse short- and long-term consequences, but it might also prolong fetal exposure to inflammation, infection, and acute obstetric complications, potentially associated with neonatal death or long-term sequelae. The primary objective of this study is to assess whether short-term (48 h) tocolysis reduces perinatal mortality/morbidity in PPROM at 22 to 33 completed weeks of gestation.

Methods
A randomized, double-blind, placebo-controlled, superiority trial will be performed in 29 French maternity units. Women with PPROM between 220/7 and 336/7 weeks of gestation, a singleton pregnancy, and no condition contraindicating expectant management will be randomized to receive a 48-hour oral treatment by either nifedipine or placebo (1:1 ratio). The primary outcome will be the occurrence of perinatal mortality/morbidity, a composite outcome including fetal death, neonatal death, or severe neonatal morbidity before discharge. If we assume an alpha-risk of 0.05 and beta-risk of 0.20 (i.e., a statistical power of 80%), 702 women (351 per arm) are required to show a reduction of the primary endpoint from 35% (placebo group) to 25% (nifedipine group). We plan to increase the required number of subjects by 20%, to replace any patients who leave the study early. The total number of subjects required is thus 850. Data will be analyzed by the intention-to-treat principle.

Discussion
This trial will inform practices and policies worldwide. Optimized prenatal management to improve the prognosis of infants born preterm could benefit about 50,000 women in the European Union and 40,000 in the United States each year.

Trial registration
ClinicalTrials.gov identifier: NCT03976063 (registration date June 5, 2019).