Progesterone gel was found to reduce the risk of giving birth before the 33rd week of pregnancy by 45% for women with a short cervix, a NIH (National Institutes of Health) study found. The cervix, part of the uterus, opens and gets shorter during labor. Women with a short cervix have a much higher risk of giving birth prematurely.

The study has been published in Ultrasound in Obstetrics and Gynecology.

Babies also benefit from progesterone treatment, the researchers found - their chances of developing neonatal respiratory distress syndrome is much lower. Neonatal RDS (respiratory distress syndrome) is a common complication among premature babies. The infant has difficulty breathing because their lungs have not fully developed.

Preterm infants have a significantly higher risk of dying early and having long-term health and developmental problems. The NIH informs that 12.9 million infants were born prematurely globally. In the USA, 12.8% of babies were born prematurely in 2008. Preterm babies also have a risk of cerebral palsy, blindness, deafness and learning disabilities.

Roberto Romero, M.D., program head for Perinatology Research and Obstetrics and chief of the Perinatology Research Branch, said:

"Our study demonstrates that progesterone gel reduces the rate of early preterm delivery - less than 33 weeks - in women with a short cervix. Women with a short cervix can be identified through routine ultrasound screening. Once identified, they could be offered treatment with progesterone."

Dr. Romero says progesterone is vital to keep a pregnancy going. He added that a short cervix appears to be linked to low progesterone levels. Romero and team therefore presumed that for women with a short cervix, progesterone therapy might prolong a pregnancy.

They randomly assigned 458 women with a short cervix to receive either a vaginal gel progesterone preparation or a placebo between the 19th and 23rd week of pregnancy. A short cervix is one that is between 10 and 20 millimeters.

They found that the women on progesterone therapy had an 8.9% chance of premature delivery at less than 33 weeks of pregnancy, compared to a 16.1% among the women on a placebo. The differences were also there for births before 28 and 35 weeks: Born before 28 weeks
Progesterone 5.1%
Placebo 10.3% Born before 35 weeks
Progesterone 14.5%
Placebo 23.3% 3% of infants born to women on progesterone therapy had respiratory distress syndrome, compared to 7.6% of those in the placebo group.

"Vaginal progesterone reduces the rate of preterm birth in women with a sonographic short cervix: a multicenter, randomized, double-blind, placebo-controlled trial"
Sonia S. Hassan, Roberto Romero, Dommeti Vidyadhari, Shalini Fusey, Jason Baxter, Meena Khandelwal, Jaya Vijayaraghavan, Yamini Trivedi, Priya Soma-Pillay, Pradip Sambarey, Ashlesha Dayal, Valentin Potapov, John O'Brien, Vladimir Astakhov, Oleksandr Yuzko, Wendy Kinzler, Bonnie Dattel, Harish Sehdev, Liudmila Mazheika, Dmitriy Manchulenko, Maria Teresa Gervasi, Lisa Sullivan, Agustin Conde-Agudelo, James A. Phillips, George W. Creasy
Ultrasound in Obstetrics and Gynecology DOI: 10.1002/uog.9017