Progesterone is a hormone that plays a significant role in reproductive health. It is often called a “pregnancy hormone” due to its functions in establishing and maintaining pregnancy.
Progesterone’s Essential Role
Progesterone is primarily produced by the corpus luteum, a temporary structure in the ovary after ovulation. This hormone prepares the uterine lining (endometrium) for a fertilized egg’s implantation. It thickens the lining, creating a receptive environment for an embryo to attach and grow.
If pregnancy occurs, progesterone maintains this thickened uterine lining, preventing shedding that would lead to menstruation. It also relaxes uterine muscles, suppressing contractions that could lead to early pregnancy loss. The hormone supports the developing placenta and prepares the breasts for milk production later in pregnancy.
Normal Progesterone Changes in Early Pregnancy
Progesterone levels naturally fluctuate throughout early pregnancy. In the first trimester, typical serum levels range from 10 to 44 ng/mL, though these ranges can vary by laboratory and individual factors.
A temporary dip in progesterone can occur during the “luteal-placental shift,” a normal transition. This shift, usually between weeks 6 and 8 of gestation, is when the placenta gradually takes over progesterone production from the corpus luteum. Levels might temporarily decline, with some studies showing the lowest levels around week 7, before rising as the placenta assumes full responsibility.
Concerning Reasons for a Progesterone Drop
While some fluctuations are normal, a significant or sustained drop in progesterone can indicate an underlying concern. A common reason for a concerning drop is a miscarriage, or early pregnancy loss. Low progesterone levels are often a symptom of a non-viable pregnancy, not the direct cause. An unhealthy pregnancy, often due to genetic or chromosomal abnormalities, may not produce enough human chorionic gonadotropin (hCG) to signal the corpus luteum to continue adequate progesterone production, leading to a drop.
An ectopic pregnancy is another serious condition where progesterone levels may be lower than expected. This occurs when the fertilized egg implants outside the uterus, most commonly in a fallopian tube. In such cases, the hormonal environment is suboptimal, and low progesterone levels (sometimes below 6.4 ng/mL) can indicate a problem.
Luteal phase defect (LPD) is a condition where the corpus luteum does not produce enough progesterone, or the uterine lining does not respond adequately. This can result in an insufficiently prepared uterine lining, making it difficult for an embryo to implant or sustain a pregnancy. Conditions like Polycystic Ovary Syndrome (PCOS) or premature luteolysis (where the corpus luteum stops producing progesterone too soon) can contribute to lower progesterone levels in the luteal phase and early pregnancy.
What to Do About a Progesterone Drop
If you suspect your progesterone levels have dropped, or experience symptoms like irregular spotting or abdominal cramping during pregnancy, consult a healthcare provider. These symptoms can also indicate other pregnancy complications, so medical evaluation is necessary.
Diagnosis typically involves blood tests for serum progesterone and human chorionic gonadotropin (hCG) levels, and sometimes an ultrasound to assess pregnancy viability and location. Your doctor will interpret these results based on your individual pregnancy and medical history.
Progesterone supplementation may be considered, particularly for individuals with a history of recurrent miscarriages or those undergoing fertility treatments. This can involve vaginal suppositories, oral pills, or injections. While supplementation can help prepare the uterine lining and may reduce the risk of preterm birth in certain situations, its effectiveness in preventing miscarriage varies depending on the underlying cause.