How to Know Your Fertile Days

When we were trying to conceive, I wanted as much information as possible.

Natural Family Planning lets you know your fertile days with precision.

NFP is based on observation of your “fertility signs.” Once you know what to look for, NFP is extremely reliable. For example, if you’re trying to avoid pregnancy, NFP is about 99.6% effective, comparable to the most reliable forms of hormonal contraception.

Now, it’s easy for us to know:

  • When I’m fertile
  • When I ovulate
  • When I’m not fertile (we’re not currently TTC)
  • When to expect my period
  • Whether I’m healthy overall (for example, if I didn’t ovulate, we would know that too)

Looking back, I can’t believe I didn’t learn Natural Family Planning earlier.

In this article, I’m going to show you why Natural Family Planning is so reliable. I’ll explain the different fertility signs, what they mean, and how you can observe them using simple, non-invasive methods.

How your hormones create “fertility signs”

When I speak of “fertility signs,” I’m referring to physical factors that indicate whether you can conceive at any given time.

It sounds complicated. It’s not, really.

It just means that your fertility is something you can understand and observe. It’s not a black box.

The changes in your body through your fertility cycle are governed by a predictable ebb and flow of hormones. There are four primary hormones that regulate fertility:

  • Estrogen
  • Progesterone
  • Follicle stimulating hormone (FSH)
  • Luteinizing hormone (LH)

Each of these four plays a vital role in your cycle. In general, their relative influence on each stage of your cycle looks something like this:

Follicle cycle and fertility hormones

If you want to know your fertile days, the important thing to realize is that these hormones affect your body in ways that you can easily observe.

Natural Family Planning is just a method to understand what’s going on with your body.

The specific method of Natural Family Planning that we practice is called the Sympto-Thermal method. With the Sympto-Thermal method, you observe two fertility signs:

  1. Cervical fluid
  2. Basal body temperature (BBT)

Each of these fertility signs is very reliable by itself. In fact there are methods of Natural Family Planning that use only cervical fluid or only BBT, not both.

I like the Sympto-Thermal method because it uses two fertility signs, so it’s extra reliable. If I’m uncertain about one sign, I can always look at the other sign to check.

It’s pretty easy to observe cervical fluid

You’ve known about cervical fluid ever since you first got your cycle. But maybe you’re like me, and no one told you what it meant.

Without cervical fluid, sperm can’t survive for more than a few hours.

But when cervical fluid is present, sperm can live – and fertilize an egg – for up to five days.

Cervical fluid does some amazing things:

  • Nourishes sperm and helps them to survive
  • Helps prepare sperm to penetrate the egg
  • Filters out abnormal sperm

Cervical fluid isn’t always present. In fact, for most of your cycle, you don’t have any cervical fluid. The cervix makes cervical fluid in the days leading up to ovulation, under the influence of estrogen, which is the dominant hormone in your cycle at that time.

When cervical fluid is not present, you’re not fertile, both because you’re not probably not close to ovulation, and because sperm can’t survive without cervical fluid.

Presence of cervical fluid/mucus throughout the fertility cycle

Cervical fluid has different characteristics, which change day to day through your cycle. During your fertile days, your cervical fluid may change from pasty, to watery, to egg-white texture, and back again.

Natural Family Planning teaches you how to recognize the changes in your cervical fluid. These changes are one of the best indicators of your fertility at any given moment.

How your basal body temperature helps you know when you ovulate

Your basal body temperature, or BBT, is your lowest core body temperature of the day. It occurs just as you wake up in the morning, because your metabolism has slowed as you slept.

Before ovulation, the dominant ovarian hormone in your cycle is estrogen. Under the influence of estrogen, your BBT is low.

After ovulation your BBT rises under the influence of progesterone, as your body builds up the endometrium of your uterus in preparation for a potential pregnancy.

For me, my BBT rises about 1 degree Fahrenheit after ovulation. For you, your specific temperature changes may be different.

The important thing to understand is the pattern. After ovulation, you’ll see a distinct rise in BBT, which looks like this:

A chart of your daily BBT can tell you all kinds of things about your cycle.

I can’t believe I never learned this before

It honestly makes me a little angry.

When I was younger, when I was first married, I felt like I had no control over my fertility. Everything was uncertain. To make matters worse, I thought the only way to make progress was through invasive and expensive tests.

Now I’m confident. I know what I’m doing. My husband and I communicate about our fertility. We work together.

Will NFP work for you and your relationship?

That’s for you and your partner to decide.

Click below to watch the free video lesson that goes with this article.

Free NFP Lessons

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