During pregnancy, hormone levels change. In the case of progesterone, levels begin to change as soon as you ovulate. After ovulation, the remnant of the follicle that contained the egg, called the corpus luteum, produces progesterone. When you're pregnant, progesterone maintains the uterine lining so the growing embryo can implant and grow. Progesterone also causes some, but not all, of the symptoms of pregnancy; estrogen and human chorionic gonadotropin also cause symptoms. Even if your progesterone level is lower than normal, you may still have some of the symptoms of pregnancy.
Progesterone does cause some of the symptoms of early pregnancy, including some you may experience each month, like sore breasts, although increasing estrogen levels also contribute. Growing breast tissue intensifies sore breasts in early pregnancy, with tingling in the nipples and sometimes extreme sensitivity to touch. Progesterone can also make you tired and may cause acne, which you may also experience each month before your period starts. Progesterone also quells cramping by relaxing smooth muscles and decreasing uterine contractions. If you have low progesterone, you may not experience these symptoms as intensely. You may also have spotting if progesterone levels don't maintain the uterine lining well.
Human Chorionic Gonadotropin Symptoms
The hormone produced by the growing placental tissue, human chorionic gonadotropin, also produces some of the symptoms of pregnancy. Known as hCG, production of this hormone signals the corpus luteum to keep producing progesterone so that you don't get a menstrual period while pregnant. After around 14 weeks, the placenta takes over progesterone manufacturing and the corpus luteum degrades. The urine and blood tests that determine pregnancy test your hCG levels. This hormone causes one of the time-honored symptoms of pregnancy, morning sickness. If you need to urinate frequently, you can also thank hCG for this symptom, caused by increased blood flow to the pelvis. These symptoms will not disappear if you have low progesterone levels, but may fade if hCG levels decrease, as happens if the pregnancy stops progressing.
Estrogen, along with progesterone, contributes to the breast changes so prominent in early pregnancy, including the bluish network of veins below the skin. Estrogen also increases blood flow, which can cause the stuffy nose from increased congestion in the blood vessels that often occurs in early pregnancy. Having low progesterone alone does not affect these symptoms.
You can't tell whether your progesterone is low by a lack of pregnancy symptoms, since other hormones also cause pregnancy symptoms. If your progesterone is low because the pregnancy is not progressing normally, you will also most likely have low hCG and estrogen levels; in this case, your pregnancy symptoms may disappear. If you have a known problem with low progesterone and repeated miscarriage, taking supplements starting after ovulation and continuing until the placenta takes over progesterone production around nine to 10 weeks of pregnancy may help prevent miscarriage, Penn Medicine reports. Most miscarriages occur because of abnormal chromosomes and progesterone supplements will not help.