Progesterone is an important hormone that helps maintain a healthy pregnancy. But there's debate about how — or whether — low progesterone levels affect pregnancy. Here’s what you need to know.
What is progesterone?
Progesterone is one of the key hormones needed to sustain a healthy pregnancy — and its name says it all: pro-gestation. It helps mature and maintain the uterine lining, preparing the uterus for a potential pregnancy.
Early on, progesterone is produced by the ovarian corpus luteum, the follicle that releases the egg during ovulation. Once conception occurs, the pregnancy hormone human chorionic gonadotropin (hCG) signals the corpus luteum to continue producing progesterone until around the second month of pregnancy. At that point, the placenta takes over production.
Throughout pregnancy, progesterone keeps the uterine lining thick and healthy, ensuring the right environment for your growing baby.
What does it mean if you have low progesterone levels?
A normal level of progesterone is needed for a pregnancy to progress, and as time goes on, those levels will increase. What’s considered normal:
- First trimester: 11.2 to 90 nanograms per milliliter (ng/ml)
- Second trimester: 25.6 to 89.4 ng/ml
- Third trimester: 48 to over 300 ng/ml
Levels that fall significantly below normal (under 5 ng/ml in the first few weeks of pregnancy, for instance) are considered low.
That said, low progesterone during pregnancy is uncommon. In fact, you're unlikely to have your progesterone levels tested unless your practitioner has a specific concern.
Keep track of your pregnancy journey, get expert advice, and connect with other moms with similar concerns in the What to Expect app.
What causes low progesterone?
Low progesterone in early pregnancy is most often associated with:
- An ectopic pregnancy
- A miscarriage
- A threatened miscarriage (vaginal bleeding, spotting and/or cramping in the first trimester)
How can low progesterone affect pregnancy?
There’s ongoing debate about whether low progesterone directly affects pregnancy. Some experts believe that progesterone deficiency may interfere with implantation or make it harder for a pregnancy to continue by preventing the uterine lining from fully developing.
Others argue that low progesterone isn't the cause of pregnancy problems but rather a result of them.
Does low progesterone increase your chance of miscarriage?
It’s not entirely clear.
Women who experience a miscarriage often have lower progesterone levels. But experts aren’t sure whether low progesterone causes the miscarriage — or whether progesterone levels drop because the pregnancy was no longer developing normally.
Since progesterone is essential for supporting early pregnancy, it makes sense to wonder whether low levels might play a role. However, most research hasn’t shown that routinely taking progesterone prevents miscarriage.
Large studies and reviews have found that progesterone treatment doesn’t significantly lower miscarriage rates or improve the chances of an ongoing pregnancy for most women. That said, your personal history may matter.
One large study found a small increase in birth rates among women who had early pregnancy bleeding and a history of one or more miscarriages. For women who had experienced three or more previous miscarriages, the benefit was more noticeable: About 72% of those who took progesterone had a live birth, compared with 57% who received a placebo.
If you’ve had a miscarriage before, talk with your healthcare provider. They can help you weigh the potential benefits and decide whether progesterone supplementation makes sense for you.
As one What to Expect Community mom, rebeccasecondgo, shared: “I had two miscarriages and then on my third pregnancy I started taking progesterone as soon as I found out I was pregnant — and now I have a beautiful, healthy 22-month-old.”
How is low progesterone treated?
If your doctor believes that low progesterone may be contributing to recurrent miscarriages, they may recommend supplemental progesterone. Progesterone can be given as:
- Injections
- Vaginal suppositories or gel
- Oral tablets
For women with recurrent miscarriages, progesterone may be started before conception and continued through early pregnancy.
Does low progesterone cause fertility issues?
Most experts agree that low progesterone (or a luteal phase deficiency — when the luteal phase of the menstrual cycle is too short and therefore progesterone levels remain too low) has limited clinical significance on its own and isn't considered a proven cause of infertility.
In many cases, a short luteal phase reflects another underlying hormonal issue, such as thyroid dysfunction. Treating the underlying problem typically restores normal progesterone levels.
Research hasn't shown that progesterone supplementation improves fertility outcomes for most women.
Can low progesterone affect IVF?
IVF cycles are different from natural cycles. Certain fertility medications suppress the body’s natural progesterone production, so progesterone must be supplemented during early pregnancy.
In IVF pregnancies, progesterone — given as injections, or vaginal gel or suppositories — is routinely prescribed during the first two to three months to support the developing pregnancy.
Can progesterone help prevent preterm birth?
In some cases, yes.
If you’ve delivered prematurely in a previous pregnancy and are now carrying one baby (not multiples), your doctor may recommend supplemental progesterone. Some studies have shown that getting weekly shots of progesterone starting at between 16 and 20 weeks of pregnancy and continuing through week 36 may reduce the risk of preterm birth, although newer research has questioned the benefit.
Both the American College of Obstetricians and Gynecologists (ACOG) and the Society for Maternal-Fetal Medicine recommend that women with a history of preterm birth discuss progesterone supplementation with their doctors.
If you don't have a history of preterm birth and your doctor finds that your cervix has shortened below 2 centimeters when you're 16 to 24 weeks pregnant (which may increase the risk of a preterm birth), they may prescribe a daily vaginal progesterone gel through 37 weeks. In these cases, progesterone has been shown to reduce the risk of preterm delivery.
Talk with your provider if you think supplementation is appropriate for you.
Should you use OTC progesterone creams?
No. Over-the-counter progesterone creams aren't regulated, which means there are no set standards for their formulation and dosage. There's also no reliable evidence that they're effective.
What’s more, some types of progesterone cream don't significantly increase in progesterone levels. If supplementation is needed, your doctor can prescribe a regulated, properly dosed option.
Are there any side effects of progesterone supplements?
Side effects vary, depending on the form. Some women experience none at all. Here are the most common.
Progesterone vaginal suppositories may cause:
- Vaginal irritation
- Itching or burning
- Yeast infections
- Cramping
- Increased vaginal discharge
They can also be messy. "I find it helps with the discharge if I lay down after inserting them, for 30 minutes to an hour," says What to Expect Community member mrsthomas1014.
Another member, FirstTimeMommy2B10, says, "If they help my pregnancy along, I am more than happy to deal with the 'icky' mess as long as I need to."
Progesterone shots may cause:
- Pain, swelling, or bruising at the injection site
- Headaches or migraines
- Breast tenderness
- Drowsiness or dizziness
- Fluid retention and bloating
- Hot flashes
- Constipation
- Weight gain
"I got pregnant through IVF so I take daily progesterone injections," says What to Expect Community member greenbean2026. "I don’t have any side effects!"
Community member ElizBu also got pregnant through IVF. She takes vaginal tablets and a daily injection. "It's a pain, but honestly it's very manageable. I've noticed I usually feel a little worse in the evenings after my shot, but it's well worth it for the extra layer of protection!"
Oral progesterone may cause:
- Headache
- Breast tenderness or pain
- Upset stomach
- Vomiting
- Diarrhea
- Constipation
- Tiredness
- Muscle, joint, or bone pain
- Mood swings, irritability, or depression
- Runny nose, sneezing, or coughing
- Vaginal discharge
- Problems urinating
Let your doctor know if you're experiencing side effects. And get immediate medical help if you have signs of an allergic reaction (itching, hives, breathlessness, swelling, fainting), vaginal bleeding, severe abdominal pain or persistent vomiting, depression, or excessive tiredness or drowsiness.
There's no clear consensus that low progesterone alone causes miscarriage or infertility. Most research shows that routine progesterone supplementation doesn't prevent miscarriage or improve fertility outcomes for most women.
However, progesterone therapy may reduce the risk of preterm birth in certain high-risk pregnancies and may benefit some women with recurrent pregnancy loss.
If your provider recommends progesterone, follow their guidance. And if you’ve been told your levels are low, try not to panic — in most cases, it’s not a cause for concern.
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