Introduction
Preterm birth is birth before 37 weeks of gestation.1 It can be induced or spontaneous (two-thirds of cases).2 In 2014, 14.84 million infants were born prematurely worldwide, comprising 10.6% of live births.3 In France, preterm birth represented 6% of singleton live births in 2016 (vs 4.5% in 1995).4 Preterm birth is associated with a significant increase in short- and long-term neonatal and infantile morbidity.5 Risk factors for spontaneous preterm birth are previous preterm birth, multiple gestations and abnormalities of the reproductive organs, vaginal infections, underweight or obesity before pregnancy, placenta previa, diabetes mellitus and gestational diabetes mellitus, maternal age, drug use, and smoking. Among the risk factors, a midtrimester sonographic short cervix is a good predictor of preterm birth.6, 7, 8 Thus, a previous study on asymptomatic patients with a singleton pregnancy and no history of preterm birth showed that cervical length ≤15 mm exposed them to a risk of delivery before 32 weeks of gestation of ≥50%.9 In France, cervical length screening of singleton pregnancies is recommended for women with a history of preterm birth but not systematically in other cases.1 In the United Kingdom and the United States, the National Institute for Health and Care Excellence (NICE) guidelines and the American College of Obstetricians and Gynecologists recommend midtrimester cervical length screening in case of singleton pregnancy and previous preterm birth or midtrimester loss.10,11 However, most guidelines except 2 advised against universal cervical length screening in singleton pregnancy.12,13 In the absence of previous preterm birth when an asymptomatic short cervix is detected (cervical length ≤25 mm without regular and painful uterine contractions), vaginal progesterone is recommended.1,14, 15, 16, 17 Progesterone is known for its immunomodulatory and antiinflammatory effects, and for its inhibitory effects on uterine contractions and the production of prostaglandins, responsible for cervical ripening.18 Administration of vaginal progesterone acts on the adaptive immune system by increasing the proportion of decidual CD4+ regulatory T cells.19 A 2012 meta-analysis showed that the use of vaginal progesterone in cases of singleton pregnancies with an asymptomatic short cervix significantly reduced the rate of preterm birth before 33 weeks’ gestation (12.4% vs 22.0%; odds ratio [OR], 0.58; 95% confidence interval [CI], 0.42–0.80).20 In the case of an asymptomatic short cervix with a history of preterm birth or late miscarriage, cervical cerclage is also recommended.1,15,21, 22, 23 In France, pessary is not recommended for this indication because of contradictory results concerning its efficacy. Vaginal progesterone and cerclage are equally effective in preventing preterm birth in women with a singleton gestation, previous spontaneous preterm birth, and a short cervix.15,24 However, a combination of these methods seems to give better results in reducing preterm birth rates, including those of pregnancies with a short cervix <10 mm.25 Spontaneous preterm birth with a personal history of preterm birth currently represents 10% of spontaneous preterm births in France.1 Therefore, 90% of spontaneous preterm births occur in patients without a history of preterm birth, but these are not detected because there is currently no universal cervical length screening program.26 Two retrospective studies showed that a universal cervical length screening program enabled to significantly reduce the rate of preterm birth.27,28 However, these results need to be verified in larger prospective cohorts. On this background, our study prospectively assessed the impact of a program for universal transvaginal ultrasound cervical length screening and treatment in cases of asymptomatic short cervix on the preterm birth rate, and its medical consequences.AJOG at a Glance
To the best of our knowledge, no study has evaluated the effect of introducing a universal transvaginal cervical length screening program on the preterm birth rate in a European country.
In a before-and-after study, the introduction of a universal transvaginal cervical length screening program in the South East of France was associated with a significant reduction in the singleton preterm birth rate (from 5.8% to 5.6%; adjusted odds ratio, 0.92; 95% confidence interval, 0.89–0.95; P<.029). In the prospective cohort study (ECHOCOL), the introduction of a universal transvaginal cervical length screening program was associated with a nonsignificant decrease in the rate of preterm birth at <37 weeks’ gestation (from 5.8% to 5.5%; adjusted odds ratio, 0.72; 95% confidence interval, 0.51–1.03; P=.068).
Our study showed a decrease in the rate of preterm birth within a large cohort in France after the implementation of a universal policy of cervical length screening to identify asymptomatic short cervix and provide preterm birth preventive treatment.