07/30/2025 11:40 a.m.

Family Planning Made Simple with a Natural Fertility Tracker

Dr. Niels van de Roemer
Dr. Niels van de Roemer Medical Adviser

Plan a baby with Daysy: simple, natural and time-saving!

Family planning works best when you truly understand your cycle. Knowing your fertile window and the biological signs that support conception can make a significant difference when you’re trying to get pregnant. With a science-based fertility tracker, you can identify ovulation more precisely than with traditional calendar methods, giving you greater confidence and reducing the stress and guesswork that often come with trying to conceive.

How daysy helps you plan your pregnancy naturally

Ready to put your baby plans into motion? Daysy offers a straightforward and natural way to track your fertility and pinpoint your fertile days.

Here’s how it works: 

Each morning, before getting out of bed, you take your basal body temperature. Place Daysy’s sensitive temperature sensor under your tongue and wait about 60 seconds. The device may ask you to confirm whether you’re on your period and that’s all it takes. Immediately after the measurement, Daysy displays your fertility status for the day.

A red light means that you are currently fertile/possibly fertile and can become pregnant through unprotected sex. A green light means that you are currently not fertile. A yellow light indicates that Daysy is still getting to know you or that your cycle is currently irregular. The algorithm first needs to acquaint itself with you andyour cycle.

Why perfect timing matters in family planning

Many women want more control over when they become pregnant and Daysy supports that by calculating your fertile window. Understanding your timing gives you the best possible chances for a pregnancy during every cycle. There is obviously no guarantee for quick conception, because your body will decide for itself when it is ready to fall pregnant. Even if you have regular sex on your fertile days, it can take months for you to fall pregnant. Please do not be disappointed if it does not immediately work out as planned.

The most important factor is to have sex during your fertile window. But additional factors also play a role: One of the sperm has to succeed in reaching the egg and breaking through its outer layer. Because this will not always work out, fertilization will not always take place. In other cases, fertilization takes place but the fertilized egg does not get nested in. This can have several causes that do not necessarily have to do with your fertility or that of your partner. Just be patient: Physical reasons are rarely the cause for why it takes longer for some couples.

The DaysyDay App offers ideal support for your family planning

There may be times when intimacy needs to be scheduled, even if that feels less spontaneous. Busy work schedules, parenting demands or travel can limit opportunities for intercourse. The DaysyDay cycle app helps by showing your predicted fertile days for the upcoming month, allowing you and your partner to plan ahead.

After several cycles of using Daysy, these predictions become even more precise. This is especially useful if sperm motility or lifespan is reduced, as the fertile window in such cases becomes narrower. With Daysy and the DaysyDay app, you can make informed decisions, stay connected as a couple and fully use your most fertile days.

Take control of your fertility journey and know your fertility status every day. Daysy is a reliable companion for natural family planning and reproductive awareness.

What is the best way to measure?

For optimal use of Daysy, we recommend that you should have slept sufficiently (at least one hour) before the measurement. It is important that you take your temperature immediately after waking up, before getting up and becoming active. Measure below your tongue, with your mouth closed, and keep the device steady while it is measuring. Video Tutorial

Do I have to measure at the same time every day?

No. You should have at least one hour of good quality sleep before the measurement. It is important that you take your temperature immediately after waking up, before getting up and becoming active. For optimal use of Daysy, try to get at least 3 or more hours of sleep before measuring. Less sleep can result in more temperature fluctuations causing Daysy to give more fertile or potentially fertile days.

How do I enter or edit menstruation?

You can confirm or remove menstruation at any time during the current day. Simply press the button to turn on your Daysy, and then press and hold the activation button until the violet light lights up without flashing and you hear a "beep." Confirm you are menstruating for each day of active bleeding and for a minimum of three consecutive days. You can also remove menstruation data for the same day by turning Daysy on and pressing and holding the activation button until the purple/blue light is no longer solidly lit and begins flashing again.

Video Tutorial

How long until Daysy knows my personal cycle?

The first 2-4 cycles of use are considered Daysy's learning phase. Over the course of her learning phase, Daysy will come to understand your cycle and begin narrowing down your fertile window. Daysy remains quite cautious and conservative during this time, which is why Daysy is accurate starting the very first day.

When can I start to rely on Daysy's results?

You can rely on Daysy's results starting the very first day of use. In the beginning, you will see more yellow and red days because Daysy is still learning your unique cycle. You will see more green days as Daysy comes to understand your cycle and can narrow down your fertile window. The more regularly you measure, the better.

My cycle is irregular. Can I still use the devices?

Yes. Irregular cycles are not a problem for Daysy/Lady-Comp. Even with irregular cycles, all Valley devices distinguish between non-fertile and fertile days with a very high accuracy. However, in case of extreme fluctuations between cycles it will give you more red and yellow lights and less green lights. Fluctuations of several days are usually not a problem. If you have questions about your unique cycle, please reach out to our team of experts.

Are there any costs associated with the DaysyDay app?

No! DaysyDay is free! There are no in-app purchases or upgrade fees.

Does illness reduce the reliability of the device?

In general, you should skip measurements during illness and while you are taking medication that can have an influence on your body temperature or cycle. If you have doubts, contact your doctor or our customer service team.

More: Contact

Get more information

If you’re ready to start a family, read on to learn helpful tips to enhance your fertility and prepare for pregnancy.

The fertility tracker method is a modern, digital evolution of natural family planning. It eliminates common sources of error – ensuring ovulation is accurately detected and recorded.

Below, we’ll show you how traditional NFP (Natural Family Planning) rules differ from the features of modern fertility monitors – and how the two compare.