Why Your Doctor Prescribed Progesterone During Pregnancy
Your doctor prescribed progesterone to reduce your risk of miscarriage or preterm birth, depending on your specific pregnancy history and current symptoms.
Most Common Reasons for Progesterone in Pregnancy
If You Have a History of Previous Preterm Birth
If you delivered a baby prematurely before (between 20-36 weeks), you should receive 17-alpha hydroxyprogesterone caproate (17OHP-C) injections at 250 mg intramuscularly weekly, starting at 16-20 weeks of gestation until 36 weeks. 1 This reduces your risk of having another preterm delivery by approximately 34% and also decreases serious complications for your baby including brain bleeding, intestinal problems, and need for oxygen support. 1
- The Society for Maternal-Fetal Medicine strongly recommends 17OHP-C injections (not vaginal progesterone) for women with prior spontaneous preterm birth, as multiple large trials show vaginal progesterone does not work effectively in this specific population. 1
If You Have Early Pregnancy Bleeding
If you are experiencing vaginal bleeding in early pregnancy (first 12 weeks), especially if you have had one or more previous miscarriages, vaginal micronized progesterone 400 mg twice daily can increase your chance of having a live birth. 2, 3
- For women with both bleeding AND a history of 3 or more previous miscarriages, progesterone increases live birth rates from 57% to 72% (a 15% absolute improvement). 2, 3
- For women with bleeding AND any history of previous miscarriage(s), progesterone increases live birth rates from 70% to 75%. 2, 3
- The treatment should continue from when bleeding starts until 16 weeks of gestation. 3
If You Have a Short Cervix (Without Prior Preterm Birth)
If ultrasound shows your cervix is ≤20 mm in length during the second trimester and you have NOT had a previous preterm birth, vaginal progesterone reduces your risk of preterm delivery. 1 This decreases preterm birth before 34 weeks by approximately 34%. 1
If You Have Recurrent Miscarriages (Without Current Bleeding)
The evidence here is less clear. If you have had 3 or more unexplained miscarriages but are NOT currently bleeding, progesterone may have limited benefit. 4 However, if you develop bleeding during this pregnancy, progesterone becomes beneficial as described above. 2, 3
If You Have Subchorionic Hemorrhage
For bleeding related to subchorionic hemorrhage specifically, oral progesterone 400 mg daily may be recommended, typically continuing until 34-37 weeks of gestation. 5
Important Clinical Points
Route of administration matters significantly:
- Injectable 17OHP-C is the only proven form for preventing recurrent preterm birth in women with prior preterm delivery. 1
- Vaginal progesterone works for short cervix (without prior preterm birth history) and for early pregnancy bleeding. 1, 2
- Do not switch from 17OHP-C injections to vaginal progesterone even if your cervix shortens during pregnancy, as there is no evidence this helps. 1
Safety profile:
- Progesterone has no significant short-term safety concerns identified in large trials. 2, 3
- The evidence on congenital abnormalities is reassuring but limited, showing no increased risk. 6
Progesterone works by:
- Reducing uterine contractions and maintaining uterine relaxation. 7
- Modulating your immune response to prevent rejection of the pregnancy. 7
- Supporting the placental attachment and development. 7
Your doctor likely prescribed progesterone based on one or more of these specific indications after reviewing your pregnancy history and current symptoms. The specific type (injection vs. vaginal vs. oral) and timing were chosen to match your particular risk factors.