Vaginal progesterone is a form of the hormone progesterone delivered directly into the vagina through an insert, suppository, or gel. It’s prescribed for two main reasons: supporting early pregnancy during fertility treatments and reducing the risk of preterm birth in women with a short cervix. Because the hormone is absorbed locally through the vaginal lining, it reaches the uterus at higher concentrations than oral forms while producing fewer whole-body side effects like drowsiness.
Why Progesterone Matters in Pregnancy
Progesterone is sometimes called the “pregnancy hormone” because of how central it is to establishing and maintaining a pregnancy. After ovulation, the ovaries produce progesterone to thicken the uterine lining so a fertilized egg can implant. If implantation succeeds, progesterone keeps that lining stable and prevents the uterus from contracting too early. When progesterone levels drop too low, the risk of miscarriage or preterm labor increases.
Vaginal progesterone supplements what the body may not be producing on its own. During IVF and other fertility treatments, the egg retrieval process disrupts the ovary’s normal progesterone production, so supplementation fills that gap during the critical early weeks. Later in pregnancy, vaginal progesterone can help keep the cervix from opening too early in women at risk for preterm delivery.
Use During Fertility Treatments
After an embryo transfer during IVF, vaginal progesterone is one of the most common ways to provide what’s called luteal phase support. This is the stretch of time between embryo transfer and the point when the placenta takes over hormone production, typically around 8 to 10 weeks of pregnancy. Without supplemental progesterone during this window, the uterine lining can break down before the embryo has a chance to establish itself.
Large reviews of clinical trials have found that variations in the exact timing or dosage of vaginal progesterone don’t significantly change how well it works for this purpose. Your fertility clinic will give you a specific protocol, but the reassuring takeaway is that the approach is flexible and well-studied.
Preventing Preterm Birth
The other major use for vaginal progesterone is reducing the risk of delivering too early. The key factor here is cervical length. A cervix shorter than 25 millimeters, measured by ultrasound between 16 and 24 weeks of pregnancy, signals an increased risk of preterm birth. For women with this finding, daily vaginal progesterone starting between 20 and 24 weeks and continuing until 34 weeks has been shown to lower that risk.
The guidelines around this have become more specific in recent years. The American College of Obstetricians and Gynecologists (ACOG) recommends vaginal progesterone for women with a singleton pregnancy, a history of preterm birth, and a confirmed short cervix. Importantly, ACOG’s updated guidance clarifies that vaginal progesterone should not be offered to women with a history of preterm birth if their cervix is not shortened. The evidence simply doesn’t support its use in that situation. It also does not appear to reduce preterm birth risk in women carrying twins or other multiples.
Available Forms
Vaginal progesterone comes in three main forms:
- Vaginal inserts are small, solid tablets placed into the vagina with a disposable applicator. Endometrin is one common brand, available as a 100 mg insert.
- Vaginal gels come in pre-filled applicators and are squeezed directly into the vaginal canal.
- Suppositories are soft, waxy capsules that melt at body temperature after insertion. These are often compounded by a pharmacy.
All three deliver progesterone through the vaginal walls, where it’s absorbed into the surrounding tissue and uterus. Your doctor will choose a form based on the reason for treatment and what’s available at your pharmacy.
How to Use It
Vaginal progesterone is typically used once daily at bedtime. The basic routine is straightforward: empty your bladder, wash your hands with soap and water, then insert the medication using the provided applicator or your fingers, depending on the form. Push it gently but far enough into the vaginal canal that it stays in place.
Leakage is the most common practical complaint. Because the insert or suppository dissolves inside the body, some of the carrier material will come back out, usually as a waxy or chalky discharge. Wearing a panty liner overnight handles this easily. Do not use a tampon to manage leakage, as it can absorb the medication before your body has a chance to.
Bedtime dosing works well because lying down gives the medication more time to dissolve and absorb before gravity pulls any residue downward. If your prescription calls for twice-daily dosing, the second dose is usually in the morning, ideally while you can stay lying down or seated for 15 to 20 minutes afterward.
Side Effects
Most side effects are local and mild. Vaginal irritation at the insertion site is the most frequently reported issue, and it usually doesn’t require any treatment. Some women notice unusual discharge, itching, or odor beyond the normal medication residue. If that happens, it’s worth mentioning to your care team, as it can sometimes signal an infection unrelated to the progesterone itself.
Because the hormone is absorbed primarily through local tissue rather than passing through the digestive system and liver, vaginal progesterone tends to cause fewer systemic side effects than oral progesterone. Oral forms are well known for causing drowsiness and dizziness, which are much less common with vaginal administration. Some women still experience bloating, breast tenderness, or headaches, but these are generally milder.
How It Compares to Other Routes
Progesterone can also be given as an oral capsule or as an injection. Each route has trade-offs. Oral progesterone is the easiest to take but produces more sedation because the liver converts some of the hormone into compounds that act on the brain. Progesterone injections avoid that problem and deliver consistent blood levels, but they require either a clinic visit or self-injection into muscle, which can be painful and cause soreness at the injection site over weeks of use.
Vaginal progesterone sits in the middle: it avoids needles and the sedation of oral pills, while delivering high concentrations directly where they’re needed most. For fertility support, it has largely replaced injections at many clinics. For preterm birth prevention in women with a short cervix, it remains the preferred route based on current evidence.