AbstractIntroductionPreterm birth is the most common cause of neonatal morbidity and mortality. Women with twin pregnancies and a short cervical length are at high risk for preterm birth. Vaginal progesterone and cervical pessary have been proposed as potential strategies to reduce preterm birth in this high‐risk population. Therefore, we aimed to compare the effectiveness of cervical pessary and vaginal progesterone in improving developmental outcomes of children born to women with twin pregnancies and mid‐trimester short cervical length.Material and methodsThis was a follow‐up study (NCT04295187) of all children at 24 months of age, born from women treated with cervical pessary or progesterone to prevent preterm birth in a randomized controlled trial (NCT02623881). We used a validated Vietnamese version of Ages & Stages Third Edition Questionnaires (ASQ‐3) and a red flag questionnaire. In surviving children, we compared the mean ASQ‐3 scores, abnormal ASQ‐3 scores, the number of children with any abnormal ASQ‐3 scores and red flag signs between the two groups. We reported the composite outcome of perinatal death or survival with any abnormal ASQ‐3 score in offspring. These outcomes were also calculated in a subgroup of women with a cervical length ≤28 mm (<25th percentile).ResultsIn the original randomized controlled trial, we randomized 300 women to pessary or progesterone. After counting the number of perinatal deaths and lost to follow‐up, 82.8% parents in the pessary group and 82.5% parents in progesterone group returned the questionnaire. The mean ASQ‐3 scores of the five skills and red flag signs did not differ significantly between the two groups. However, the percentage of children having abnormal ASQ‐3 scores in fine motor skills was significantly lower in the progesterone group (6.1% vs 1.3%, P = 0.01). There were no significant differences in the composite outcome of perinatal death or survival with any abnormal ASQ‐3 score in unselected women and in those with cervical length ≤28 mm.ConclusionsCervical pessary and vaginal progesterone may have comparable effects on developmental outcomes in children at ≥24 months of age, born to women with twin pregnancies and short cervical length. However, this finding could be likely due to a lack of study power.