Why ovulation strips don't work for 1 in 10 women

If you are trying to conceive, you might have used or considered ovulation strips. Ovulation strips measure Luteinizing Hormone or a combination of Luteinizing Hormone and Oestrogen in urine. The level of these hormones increases before ovulation, giving you an indication of your most fertile days and allowing you to time intercourse. However, ovulation strips don’t work for everyone. In this article we explain why.

The role of LH and Oestrogen

The menstrual cycle is regulated by hormones, with levels going up and down at different phases of the cycle, allowing important developments to take place. During the follicular phase, hormones levels are low, whilst the follicles are growing and the eggs maturing. Once the eggs have reached a certain developmental state, they start producing oestrogen. As levels of oestrogen increase, a message is sent to the pituitary gland in the brain, which triggers and abrupt secretion of LH. The onset of the surge in LH precedes ovulation by 35-44h, reaching a peak 10-12 hours before ovulation. LH hormone is responsible for the last phase of egg maturation and for the egg release from the follicle (ovulation), allowing it to be fertilised by sperm. The egg survives up to 24 hours after ovulation. 

The increase in oestrogen and LH mark the most fertile period of the menstrual cycle. Because it happens before ovulation, you have around 24-48h to have intercourse and fertilise the egg.

After ovulation, the follicle becomes corpus luteum and starts producing progesterone, which triggers the uterus lining to thicken, ready to implant the fertilised egg. This is called the luteal phase of the menstrual cycle. During this phase, the levels of oestrogen and LH remain low.

Types of ovulation strips

Not all ovulation strips are the same. There are two type of ovulation strips:

• Qualitative: these strips tell you whether your LH value is below or above a certain threshold and will give you either a positive or a negative result. These strips don’t work for everyone – in fact they don’t work for about 1 in 10 women.³ Some of these strips interpret the results for you (digital tests), and show you a positive/negative sign or a smiley/sad face. Other strips only show a change in colour and you have to interpret the result yourself (have you ever found yourself wondering if the line is really there?), there is an added likelihood of error.

• Quantitative: these strips show a numeric measure of LH, usually in a concentration of mIU/mL. These tests will always tell you your LH value, regardless of whether your LH is low or high at baseline and during the surge. As not all women are the same, knowing what your normal is, can help you identify your fertile days with more accuracy. Mylo is one of these tests, that can tell you exactly your LH value, giving you a better understanding of how your LH is changing over time, what your pattern looks like and pinpointing your fertile window.

Now that you know that ovulation strips don’t work for everyone, what can you do to make sure you are able to identify your fertile window? Let us know in comments.