Cervical mucus is produced by the numerous glands present in the endo-cervix region of the female reproductive system (1). An amount of around 10-50 mg of cervical mucus is produced per day which can increase to about 500-600 mg during ovulation. Large proteins known as the mucins give it a viscous consistency. Changes in the viscosity and water content are observed during the menstrual cycle. This feature of variation in the water content of mucus allows the cervical mucus to function either as a barrier or a transport medium to the spermatozoa. Cervical mucus is composed of various electrolytes like calcium, potassium, and sodium. It also has organic components like glucose, amino acids, and proteins. Trace elements such as zinc, copper, manganese are also present. Influence of the female hormones estrogen and progesterone determine the consistency of the mucus.
During the period of ovulation, high estrogen levels are present in the body (2). The mucus secreted in this period is thin in consistency and allows the movement of sperm into the uterus. Its pH is alkaline which makes a hospitable environment for the sperm. Post-ovulation, the secretion of mucus, becomes thicker, and the pH is reduced under the action of the progesterone hormone. The acidic environment formed is inhospitable for the sperm. Thick mucus acts as a barrier to the sperm from entering into the uterus. Use of the oral contraceptive pills by women not desiring to get pregnant also causes the production of thick mucus due to the effects of progesterone.
An operculum is the cervical mucus plug (3) which forms inside the cervical canal during pregnancy. Operculum acts as a seal to protect the uterus against the leakage of the uterine fluids and also prevents the entry of pathogenic micro-organisms. This mucus plug gets released as blood-tinged mucus discharge on dilation of the cervix, usually during the childbirth.
Cervical mucus acts as an indicator of the hormonal changes in a female’s body. The five main types of the cervical mucus are:
- Sticky & dry mucus- Post menstruation mucus.
- Sticky & creamy white mucus- Pre-ovulation mucus.
- Wet & watery mucus- Pre-ovulation mucus; an indicator of impending mucus.
- Stretchy & egg white mucus- Mucus during ovulation; it is stretchable between the two fingers.
- Sticky & dry mucus- Post-ovulatory and pre-menstruation mucus.
These are the five types of changes in the mucus experienced during a menstrual cycle. The onset of the menstrual period can be judged by observing the cervical mucus after ovulation. The mucus goes from egg white color and stretchy consistency to sticky and dry with a marked decrease in the amount of mucus.
Changes in the cervical mucus can be described in detail as follows:
At the beginning of the menstrual cycle: The cycle is initiated with the onset of the menstrual period. During the menstrual period checking the consistency of cervical mucus is not possible because of the presence of blood.
During the post-menstrual period: During this period the cervical mucus can be checked by inserting two clean fingers into the vagina and palpating the cervix. At first, dry mucus will be felt on the fingers. On checking daily, it eventually becomes sticky.
On approaching ovulation: When the ovulation approaches, a little more cervical mucus is observed. It is watery and creamier.
Preovulatory mucus: Right before the beginning of ovulation, the quantity of the cervical mucus increases, and it becomes stretchy inconsistency (4). This indicates the most fertile period.
During ovulation: When a female is ovulating, the fertility reduces, and cervix is near closure. Cervical mucus may increase even more and become more watery, but it does not remain as fertile as it was before ovulation.
If the egg becomes fertilized: A white or clear creamy mucus is noticed after implantation. A little amount of blood (implantation bleeding) can also be seen along with the mucus. Mucus is necessary during early pregnancy. It helps in blocking the entrance to the cervix for prevention of the bacteria from getting in.
After the ovulation: If there is no evidence of increased cervical mucus in early pregnancy, or if the egg was not fertilized in this cycle, the cervical mucus returns to its dry state. First, it goes back to being sticky; then it dries up until next period.
During ovulation, a follicle releases a mature egg (5) in the ovarian cavity which further starts traveling in the fallopian tube towards the uterus. If fertilization occurs, it takes place in the fallopian tubes, and the egg will attach itself to the uterine wall. If fertilization does not happen, the egg will be expelled from the body during menstruation. The process of ovulation is under the influence of the hormones. In the first phase of ovulation (follicular phase), hormones cause maturation of the egg in the follicles. In the second phase (ovulation phase), an increase in the estrogen hormone leads to a rise in the luteinizing hormone (LH) and the stimulating follicle hormone (FSH). The luteinizing hormone ruptures the follicles to release the mature egg into the ovarian cavity. The stimulating follicle hormone is responsible for the growth and maturation of the follicles and the eggs inside the follicles. Ovulation occurs midway of the menstrual cycle. Monitoring the cervical mucus before and after ovulation helps in determining the time of ovulation.
A day after ovulation, cervical mucus becomes stretchy and has an egg white consistency. The mucus at this stage can be compared to a raw egg. This mucus is most favorable for the sperm to move forward and survive inside the body until they can reach the egg and fertilize it. Post ovulation, the mucus will change back to a normal clear to white color. However, the discharge from the ovulation process will dry up and become sticky. After drying up of the mucus and returning to a regular release, an increase in the excretion is observed with the egg white discharge appearing again. These events occur about a week after ovulation. It denotes the sign of implantation, where there is the attachment of the fertilized egg onto the walls of the uterus.
After the ovulation process is completed, cervical mucus changes its color from egg white to slightly white and gets dried up for a few days. Later, it retains its color. However the dried mucus gets washed away and is replaced with fluid in small quantity. The consistency of the egg white is very similar to the cervical mucus seen during ovulation.
To give a clear picture of differentiation of the appearance of cervical mucus in case of either a pregnant or a non-pregnant female, consistency of the mucus is indicative. Cervical mucus after ovulation, if pregnant, becomes thick in texture and milky white and is released in higher amounts. It is referred to as leucorrhea (6) and is considered to be an early sign of pregnancy. If pregnancy does not occur, after the ovulation, the cervical fluid undergoes changes that include drying up of the mucus to form a white, dry mucus followed by returning to the usual clear mucus.
Regular observation of the cervical mucus aids in timing the sexual intercourse for conceiving or avoiding the pregnancy.