This serves a special purpose. It causes the inner lining of the uterus to become so thickened and engorged with nutrients that it can nourish and sustain the fertilized egg if it were to imbed.
Progesterone also has an influence on the consistency of the vaginal mucus, making it thicker. This is a protective strategy which makes it harder for sperm and bacteria to migrate into the uterus and potentially cause an infection. A uterine infection at any stage of pregnancy, particularly in the early weeks, could easily lead to spontaneous miscarriage.
Progesterone also lets the pituitary—also called the master gland—know to hold back on producing FSH and luteinizing hormones if the woman is already pregnant. It is this progesterone surge which causes a woman’s basal body temperature to rise and remain higher than normal until she starts her next period. If you are taking your temperature each day, then you may notice this increase.
The other hormone which is high at this stage of the menstrual cycle is estrogen which helps to build up the lining of the uterus. It too plays a role in stimulating the endometrium—the inner lining of the uterus—to thicken.
Symptoms of the luteal phase
- Breast sensitivity. The increase in estrogen and progesterone can have an effect on the milk ducts within the breast and cause them to swell slightly.
- Cervical mucous thickening.
However, if conception has occurred, the corpus luteum plays a vital role in nurturing the early stages of the pregnancy called a blastocyst. The corpus luteum takes on this role for around 7 weeks, by which time the placenta is established and doing its job.
Human chorionic gonadotrophin hormone (hCG)
Although this may all sound confusing, your body knows what to do and when to do it. When a woman is having problems conceiving, one of many contributing factors may be a luteal phase defect.
Luteal phase dysfunction or defect
Another problem can occur if corpus luteum is not sustained as long as it should be. There is an overall drop in the amount of progesterone being produced. Although this may be high in the early days, it falls off too soon which brings on an earlier period.
Another issue can be if the lining of the uterus does not react as it should to the hormonal effects of the corpus luteum. It’s estimated that around 3 to 20% of women with infertility problems have some level of luteal phase dysfunction. In those who are able to conceive but have recurrent miscarriages, the number may be as high as 60%.
The information of this article has been reviewed by nursing experts of the Association of Women’s Health, Obstetric, & Neonatal Nurses (AWHONN). The content should not substitute medical advice from your personal healthcare provider. Please consult your healthcare provider for recommendations/diagnosis or treatment. For more advice from AWHONN nurses, visit Healthy Mom&Baby at health4mom.org.