Spontaneous preterm delivery is the most important cause of perinatal mortality in the Western world. Although women with a previous preterm birth (PTB) and women with a multiple gestations are at the highest risk of PTB, the majority of spontaneous PTBs occur in low-risk women.
Interventions for threatened PTB, such as tocolysis, bed rest, or placement of a cervical cerclage, have shown limited effectiveness. Only antenatal administration of corticosteroids improved neonatal outcome. Consequently, prevention of (the onset of) PTB is essential.
Identification of low-risk women who will deliver prematurely is crucial in the development of preventive strategies. One of the best predictors in this group is cervical length (CL), measured by transvaginal ultrasound at 20 to 22 weeks of gestation.
Recently, published studies showed promising results for progesterone in the prevention of PTB. As these studies evaluated the effect of progesterone in an unselected population with a combination of high-risk and low-risk women, the effectiveness of vaginal progesterone in a population with strictly low-risk women remains unknown.
Previous studies did not show maternal or fetal side effects of progesterone. We designed a multicenter study in low-risk women to evaluate the ability of CL measurement to detect those at increased risk for PTB.
Women with a short CL had asked to participate in a randomised clinical trial to evaluate whether subsequent progesterone treatment is effective. We defined low risk for PTB as women who did not have a history of PTB before 34 weeks of gestation. Here, we report the results of the trial, and results of the cohort will be published separately
Materials and Methods:
A multicenter double-blind placebo-controlled randomised clinical trial has performed within the Dutch Obstetric Research Consortium. It is a collaborative research effort of obstetric practices in the Netherlands. The present study has conducted in 7 university hospitals, 23 general hospitals, 29 ultrasound centres, and 160 midwifery practices. The trial has approved by the Medical Ethical Committee of the Academic Medical Center, Amsterdam, the Netherlands (MEC AMC 08–328).
Women with a low-risk singleton pregnancy and a CL 30 mm were included in our study. Low-risk pregnancy has defined as nulliparous, or multiparous women without a history of spontaneous PTB < 34 weeks of gestation. Exclusion criteria were age < 18 years, cervical cerclage, previous PTB < 34 weeks, preterm labour, or known congenital malformations.