A meta-analysis of placebo-controlled data published today indicates that vaginal progesterone reduces preterm birth and neonatal complications in women with a mid-trimester short cervix.
Progesterone is known as the pregnancy hormone and its concentration rises during the second half of the menstrual cycle to thicken the lining of the uterus, so it is ready to support the implantation of a fertilized egg. If pregnancy does not occur levels of progesterone decline again.
Once a fetus starts to develop the placenta continues to produce progesterone to prevent further ovulation. A decline in progesterone levels during pregnancy has been implicated in miscarriage and premature birth.
Premature birth is the most common complication of pregnancy, with 15 million babies being born each year before full term has been reached. Vaginal administration of progesterone is used in some countries to prevent miscarriage and has also been widely investigated as a means to lower the risk of premature birth in women found to have a short cervix at mid-trimester sonographic assessment.
The majority of studies have reported positive results. For example, in a study of 458 women with a short cervix, the rate of preterm birth before 33 weeks was reduced by 45%. However, data published in February 2016 cast doubt on the effectiveness of the treatment and the World Health Organization called for more evidence.
A meta-analysis has now been conducted on all randomized, placebo-controlled studies of vaginal progesterone used in women with a singleton gestation and a mid-trimester sonographic cervical length ≤25 mm.
The results were clearly in favor of vaginal progesterone lowering the risk of preterm birth. The rate of premature birth among women receiving vaginal progesterone was reduced at <28, <30, <32, <34, <35, and <36 weeks.
It was also shown to decrease the frequency of complications in babies who were born early and reduced the number of babies weighing less than 1500 grams. Furthermore, no deleterious effects on childhood neurodevelopment were observed.
The findings of our meta-analysis of individual patient data, which includes all available trials, should reassure clinicians and professional/scientific organizations that vaginal progesterone is efficacious and safe for reducing preterm birth and neonatal morbidity and mortality in women with a sonographic short cervix".
Lead author, Dr Roberto Romero.
Professor Kypros Nicolaides, Head of Obstetrics and Gynecology at Kings College, London, added "...recent evidence assessing the implementation of universal cervical length screening in women with a singleton gestation and treatment with vaginal progesterone to those with a short cervix suggests that this intervention could contribute to a reduction in the rate of preterm birth and associated neonatal morbidity and mortality in the United States."