Preterm labor, defined as labor occurring before 37 weeks of gestation, remains a leading cause of neonatal morbidity and mortality worldwide. According to the World Health Organization (WHO), approximately 15 million babies are born preterm each year, and this figure continues to rise in certain regions. Preterm birth is associated with a higher risk of health complications, including respiratory distress syndrome, infections, and long-term developmental delays. However, significant progress has been made in preventing preterm birth in high-risk women through the use of progesterone therapy.
What is Progesterone?
Progesterone is a hormone naturally produced in the body, primarily by the corpus luteum in early pregnancy and later by the placenta. It plays a vital role in maintaining pregnancy by:
- Preparing the uterine lining for implantation
- Inhibiting uterine contractions
- Modulating the maternal immune system to prevent fetal rejection
During early pregnancy, progesterone suppresses the immune system to ensure the developing fetus (which is genetically different from the mother) is not rejected. It also helps prevent early uterine contractions that could lead to preterm birth.
How Progesterone Helps Prevent Preterm Labor
Research shows progesterone supplementation may reduce preterm birth risk by:
- Stabilizing the uterine environment
- Reducing inflammation
- Maintaining cervical tissue integrity
- Suppressing pro-inflammatory cytokines
A landmark study in the American Journal of Obstetrics and Gynecology found progesterone treatment reduced preterm birth risk by 45% in women with a history of spontaneous preterm birth.
Forms of Progesterone Used
1. Intramuscular Progesterone (17-OHPC)
Weekly injections shown to significantly reduce preterm birth risk in high-risk women.
2. Vaginal Progesterone
Gel or suppositories effective for women with short cervix (<25mm).
3. Oral Progesterone
Less commonly used due to absorption variability and lower effectiveness.
Who Should Receive Progesterone Therapy?
- Women with prior preterm birth: 33-45% risk reduction shown
- Short cervix (<25mm): Prolongs pregnancy duration
- Multiple pregnancies: Mixed evidence, requires further study
Effectiveness and Safety
Clinical evidence shows:
- 33% reduction in preterm birth (JAMA study)
- 35% reduction in women with short cervix (BMJ meta-analysis)
- Generally well-tolerated with mild side effects
Most common side effects include injection site irritation or vaginal discomfort. Severe reactions are rare.
A Quick Review
Progesterone remains a cornerstone therapy for preventing preterm labor in high-risk pregnancies. While not universally effective, it significantly improves outcomes when properly targeted. Ongoing research continues to refine treatment protocols and expand applications.
Key Takeaways:
- Particularly effective for women with prior preterm birth or short cervix
- Multiple administration options available
- Safe with minimal side effects
- Continues to be optimized through research
