Cervical Mucus and Fertility

The importance of cervical mucus in female reproduction is usually overlooked. This natural fluid, which is produced by the cervix and which changes texture and consistency throughout the menstrual cycle, is crucial for reproductive health.

Background

Depending on hormones like estrogen and luteinizing hormone, the cervical glands secrete different types of mucus throughout the menstrual cycle. From completely closing the opening of the cervix, to filtering abnormal sperm, to allowing the sperm to survive longer and swim easier through the cervix, the presence and type of cervical mucus can indicate when a woman is most fertile. In addition, to help predict ovulation, cervical mucus plays an important role in helping sperm survive the acidic environment of the vagina.

Introduction

It has been known that cervical mucus can enhance or impede the passage of sperm through the cervical canal. During the menstrual cycle four types of cervical mucus can be identified. To elaborate, right after menstruation ends, a thick and pasty looking mucus can be observed. This type of mucus, known as Type G mucus (Guard), blocks the opening of the cervix and it is impenetrable by sperm. As the fertile window gets closer, around cycle day 12, a more liquid mucus – when compared with G mucus, is produced. Known as L mucus (Liquid) its job is to filter out the abnormal sperm. Abnormal sperm (low motility, low morphology, etc.) are not capable of swimming through this semi-thick fluid and are filtered out at the cervix. The most well-known and noticeable types of cervical mucus are Type S (Stretchy) and Type P (Potassium), secreted a few days before ovulation and during ovulation, respectively. Providing an alkaline environment, these two types of cervical mucus can protect the sperm and substantially extend their life span as they navigate through the cervix.

Vaginal Ph

In order to minimize harmful bacteria, viruses, yeast infections, and inflammation, the pH of the vagina is maintained at an acidic level – between 3.8 and 4.5. This acidic environment is created by lactic acid in the presence of the good bacteria; lactobacilli species. Unfortunately, this acidic environment is detrimental to sperm. Sperm cannot survive in such acidic environment. A paper published by Global Women’s Medicine makes reference to a study where it was found that the optimal vaginal pH to maintain sperm viability and motility ranges from 7.0 to 8.5. In fact, a study published by Fertility and Sterility concluded that a reduction in sperm motility is seen at a pH less than 6.0. 

How can sperm survive such hostile environment?

As mentioned earlier, the acidic environment of the vagina is detrimental to sperm. However, nature provides a few ways to overcome this situation:

Cervical Mucus

The least understood by health professionals, and perhaps the most important one, is cervical mucus. While cervical mucus is present throughout the entire menstrual cycle, the types secreted a few days before ovulation and during ovulation are the ones that can help sperm survive longer in the acidic environment of the vagina. Known for its stretchy, stringy and slippery consistency, this type of cervical mucus is referred as Type S. This type of cervical mucus is seen a couple of days before ovulation, and it can help a good quality sperm survive up to 5 days. The day of ovulation, a more slippery and liquid than Type S mucus can be observed. Rich in potassium, this type of mucus is known as Type P and it’s able to supercharge the sperm, giving it all the energy that it needs to reach the fallopian tube and fertilize the egg.

Semen

Another protection against this acidic environment is the semen. Sperm is only a small percentage of the total semen volume - around 5 to 10%. The rest of the semen is there to protect and nourish the sperm. The normal pH of semen is typically between 7.2 and 8.0, making it slightly alkaline. This pH range helps protect sperm from the acidic environment of the vagina. This slightly alkaline pH of semen protects sperm temporarily. However, according to a study published by Scielo in 2015, a reduction in semen volume may negatively impact fertility since buffering capacity of semen against vaginal acidity becomes inadequate. Therefore, one way of helping sperm navigate through the acidic vaginal environment is for the male partner to have a healthy semen volume – between 1.5 to 5mL. In addition to having a healthy semen volume, men should also make sure that the pH of their semen is between 7.2 and 8.

Female Orgasm

Another way to reduce the acidity of the vagina is for the woman to be sexually aroused during intercourse. According to a study published in 2015, during orgasm the vagina produces a fluid that lubricates and also elevates the vaginal pH to 7.0 within seconds. This decrease in acidity can be maintained for up to two hours after ejaculation. However, an older study concluded that orgasm only resulted in small changes of the vaginal surface pH.

Lifestyle

Lifestyle also plays a part in improving cervical mucus. Staying hydrated by drinking lots of good water, consuming foods rich in essential fatty acids such as nuts and seeds, eating lots of dark green leafy vegetables - spinach, kale, and other leafy greens are rich in folate and minerals that support healthy cervical mucus. As always, avoid dairy products - they increase mucus production and inflammation, which could negatively impact cervical mucus. Also, stay away from processed foods and sugars – they contribute to inflammation and hinder cervical mucus production. Since caffeine is a diuretic, consuming it can dehydrate the body.

TCM and cervical mucus

In TCM the body is considered to have two energies; Yin and Yang. When these energies are in balanced, the body is healthy and in perfect harmony. Among many things, the Yin energy controls fluids. As such, a lack of cervical mucus could be a sign of the TCM pattern known as Yin Deficiency. In order to identify which TCM organ is deficient in Yin, additional symptoms would need to be present. For example, in TCM the Kidneys are called the “Root of Pre-Heaven Qi” because they store Essence. This essence gets depleted with stress, lack of sleep, lack of good food, lack of exercise, overwork, etc. In modern societies where many women are working jobs requiring long hours in stressful conditions, as well as running their households, leaving no time for a healthy meals nor exercise, it is easy to see how Kidney Yin Deficiency is a common pattern amongst women trying to conceive. By nourishing the Yin of the Kidneys with acupuncture and Chinese herbal formulas, the overall Yin of the body is increased and the patient begins to see more cervical mucus.

Conclusion

Cervical mucus plays many important roles in female reproduction, from helping women understand when they will ovulate, to protecting the sperm. Unfortunately, its value in helping sperm survive longer and swim further is usually underestimated. Doing acupuncture and taking Chinese herbal medicine that increase Yin can be very effective in increasing cervical mucus. In addition, lifestyle changes (diet, habits, exercise, etc.) are usually necessary to maintain a good balance between Yin and Yang.