Cervical mucus is the female body’s in-built sperm processing laboratory, opening each and every menstrual cycle for one precious fertile window, and it plays a pivotal role in successful conception and delivery of healthy sperm to the egg. In this article, we will cover what cervical mucus is in more detail, how it helps people get pregnant, and what it does for sperm during conception.
First things first. What is cervical mucus?
Cervical mucus is a fluid produced by the cervix. Hormone changes throughout a menstrual cycle drive changes in the consistency of cervical mucus. As ovulation approaches, cervical mucus will be thick and white, and right before ovulation, the consistency changes to clear and stretchy (often compared to egg whites in colour and consistency).
Cervical mucus serves two purposes that change throughout a menstrual cycle. One purpose of cervical mucus is to prevent sperm and other substances from getting into the uterus. The other purpose is specifically encouraging and supporting healthy sperm to swim into the uterus. That latter purpose is what we’re going to be discussing in this article.
How does cervical mucus help with getting pregnant?
There is significant literature on the role of cervical mucus in encouraging conception. Many people trying to conceive are aware of what to look for, and ‘egg white consistency’ are words we hear often. What is less discussed, however, is what specifically cervical mucus does for sperm that encourages conception. We often hear ‘it helps sperm swim’, and an often used metaphor is a swimming pool: the water must be, well, watery for sperm to swim through it to the fallopian tube. Comparing one’s cervix to a swimming pool aside, it’s not a great metaphor because it misses the why. Why is cervical mucus the consistency it is when ovulation occurs? Why does it support conception?
Cervical mucus is the perfect chemical partner for sperm. It is the female body’s in-built semen processing laboratory, and its role in ensuring a healthy pregnancy is very underappreciated.
Essentially, the cervical mucus produced in the female reproductive tract performs the same functions of a laboratory – filtering out abnormal sperm, feeding sperm cells, removing semen (harmful to the uterus) and starting sperm capacitation. Let’s break it down. 👇
What does cervical mucus do for sperm?
Cervical mucus is uniquely designed to keep everything out of the uterus (thereby keeping the uterus safe), except during a fertile window (i.e., a few days before ovulation, and during ovulation), when it changes its chemical composition and consistency to deliberately let healthy sperm in. During this time, cervical mucus plays 4 main roles:
1. Cervical mucus acts as a sperm filter, so that ideally only morphologically normal sperm can enter the uterus. This is vitally important – ensuring only healthy sperm cells reach the egg and increasing the chances of a healthy pregnancy and healthy baby. How does cervical mucus do this? During the ovulatory phase, the interstices (the spaces between) in the molecular structure of cervical mucus increase in size, getting as large as the size of a sperm head. In short, during ovulation, the gaps in the molecular structure of cervical mucus get bigger, so that normally shaped sperm can push through into the uterus.
2. Cervical mucus acts as a barrier, so that nothing harmful can enter the uterus. It prevents semen (the fluid sperm is in) from entering the uterus, and also removes seminal plasma from the surface of the sperm. Seminal plasma is essentially semen - it’s all the chemical and biological ingredients in semen that are vital for sperm cells until they reach the cervix. Thereafter, they cannot be introduced into the uterus. This is why semen samples must be prepared in a laboratory for Intrauterine Insemination – seminal fluids must be removed, the sperm cells must be filtered and abnormal or unhealthy sperm cells removed.
3. Cervical mucus kicks off ‘sperm capacitation’. Sperm capacitation are the changes that sperm cells undergo in order to successfully fertilise an egg. These changes include altering their movement from swimming straight, to instead moving left to right led by powerful movements from the head of the sperm. The membrane around the sperm cell also begins to change, so that it can fuse with an egg when it gets there. No cervical mucus = no sperm capacitation which = no fertilisation.
4. Cervical mucus nurtures sperm, supporting sperm cells as they swim through the uterus and into the fallopian tubes. Motile sperm cells that make it through the cervical mucus can survive in the cervical os (the passage through the cervix into the uterus) for up to 5 days due to the protection and nutrients provided by cervical mucus. This is the often mis-quoted “sperm can survive in the vagina 7 days” idea that is passed around schools as a cautionary tale promoting use of protection in order to avoid pregnancy. Sperm cells are not surviving in the vagina – which is highly acidic and damaging to sperm – but they are surviving in the cervical canal (the passage from vaginal canal to uterus), courtesy of cervical mucus, which is specifically designed to support healthy sperm.
Your questions, answered...
Q: What’s the deal with cervical mucus?
A: It's the perfect chemical partner for healthy sperm, and filters out abnormal sperm (like an in-built sperm lab in your body).
The stretchy fluid secreted by the cervix has an important role in the conception process and is the perfect chemical partner for sperm. The components of the cervical mucus provide nutrients and protection to sperm as they make their long journey to meet the egg. Cervical mucus actually acts as a filter so only morphologically normal sperm can enter the uterus. It also facilitates the capacitation of sperm (that’s the first step of sperm activation in order to be able to fertilise an egg).
Q: Ok, so sperm needs to get up into cervical mucus. Why?
A: bacteria = bad for sperm.
It’s widely known that the presence of Lactobacillus is important for vaginal health, keeping the pH low and helping to prevent infections. However, the lowered pH in the vaginal canal can be detrimental to sperm motility and count and the Lactobacillus itself can reduce sperm motility. That’s right, the ever important vaginal microbiota that protects us from infection and reduces the risk of miscarriage – can also hinder us from getting pregnant. Bodies are complex. Sigh.
Q: Ok so cervixes are great, but how do you get up there with sperm?
A: Cervical caps (delivered up there with a specially designed applicator… hint hint).
The cervical cap within the Béa Applicator protects sperm from the vaginal environment and concentrates semen at the opening of the cervix, encouraging more sperm to travel towards the egg for fertilisation. In fact, cervical caps can deliver 3.23x more sperm into the cervical mucus than sexual intercourse or vaginal straw insemination. So, not only will a cervical cap deliver more semen to the cervical mucus, there are additional benefits of delivering a semen sample straight to the cervix – like bypassing the vaginal environment.
Q: If cervical mucus is so great, why does IUI exist?
A: It’s complicated…
With the development of IVF in the 1970s, sperm washing techniques to filter semen and concentrate healthy sperm were improved, and intrauterine insemination (IUI) was subsequently introduced as a fertility treatment. IUI is a big source of revenue for fertility clinics, and something people can try before going for IVF (essentially, IUI is not a ‘last resort’ treatment).
Q: But are there any real benefits of introducing a processed sperm sample directly into the uterus as opposed to a fresh semen sample in a cervical cap near the cervix?
A: Research indicates no.
Because ICI isn’t often performed in clinical settings anymore, it’s hard to find recent studies to demonstrate success rates, but this study from 2018 showed that the live births rates were similar for ICI and IUI. In addition, ICI carries less risk than IUI. The miscarriage rate is lower for ICI than IUI and IUI carries the risk of endometritis, cramping and bleeding.
Q: What on earth do I do now?
A: We’ve got you.
The Béa Applicator was designed to work with our brilliant, gorgeous, smart bodies, using our in-built reproductive systems, and enhancing them so that we have our best chance of getting pregnant every single cycle. If you’re interested in starting treatment with Béa but want to know more, get in touch. There are a few ways you can talk to us: send us an email or book a call with a Béa Treatment Expert or join one of our monthly free Fertility Webinars to talk to Sandy about all things TTC. We love hearing from you and want to answer all your questions.
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