Photo of a pregnant women's stomach showing a healthcare professional (only torso showing for both people) listening to the baby's heartbeat with a stethoscope to check for risks of preterm birth.
Credit: EmiliaUngur/Shutterstock

Women with a short cervix can reduce the risk of having a preterm birth by having treatment with vaginal progesterone, which is particularly helpful in women with a cervix length of 25mm or less, shows research from Amsterdam University Medical Center (UMC).

Most women have a cervical length of 35mm or more and a low rate of preterm birth of approximately 6% at less than 37 weeks. However, risk of preterm birth increases in women with shorter cervixes. For example, the risk of preterm birth before 37 weeks more than doubles to 13.8% for women with a cervix between 25–35mm and to 34.2% for those with a cervical length below 25mm (thought to impact around 6.7% of women or less).

Avoiding preterm birth, particularly before 34 weeks gestation, is important for child health. Babies born preterm are at increased risk for lifelong physical and developmental problems.

For women with a short cervix who become pregnant, options to prevent preterm birth include the application of vaginal progesterone and the use of a cervical pessary, a round silicone device inserted into the cervix at a certain point in the pregnancy to try and stop early birth.

Results of previous studies have not conclusively proved the efficacy of using a pessary versus progesterone for at risk women. This study, published in the BMJ, randomized 635 women with a singleton pregnancy (between 18–22 weeks gestation) and a cervix length between 20–35mm to use a cervical pessary or vaginal progesterone (200mg daily) to prevent preterm birth at 34 weeks or less.

The results showed no differences in outcomes between the pessary and the progesterone group in women with a cervical length between 25–35mm (481 women). However, in women with a cervical length of less than 25mm, 16% of the women in the pessary group (10 of 62 women) had a preterm birth before 28 weeks versus 4% of the progesterone group (3 of 69 women).

Progesterone treatment was also associated with a lower risk of an adverse perinatal outcome (12%) than use of the pessary (24%). These outcomes included stillbirth or early death of the baby, or the onset of syndromes linked to preterm birth like chronic lung disease and others.

“This is an important improvement that can contribute to the reduction of preterm births and the associated complications, such as an increased risk of infant mortality and long-term health problems for the child,” said lead author Eva Pajkrt, professor of obstetrics at Amsterdam UMC, in a press statement.

“Based on our study, we recommend measuring the length of the cervix of all pregnant women during the 20-week ultrasound. Women with a cervix shorter than 25 mm should be informed about the possibility of treatment with Progesterone,” she concluded.

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