What usually happens is that the process of luteinization results in the breakdown of various membranes and structures such that the follicle OPENS and releases the egg that has been maturing inside it. This is called OVULATION. In its new form, the corpus luteum is able to produce a hormone called progesterone, which is necessary for the early stages of pregnancy and helps with preparing the uterine lining for the possibility of pregnancy.

In NFP methods, the presence of progesterone can be monitored through Basal Body Tracking (to find a temperature shift), through PdG urine testing, or through family planning blood draws. USUALLY the confirmation of progesterone with one of these signs means that ovulation has successfully occurred.

BUT, in some rare cases, it's possible for a follicle to undergo the process of luteinization without actually releasing that egg. In this case, the egg is not viable and remains "trapped" inside the corpus luteum until the corpus luteum breaks down and a new cycle begins. That is what happens when you have a Luteinized Unruptured Follicle.

Why are LUFs a problem?

Experiencing a single LUF is usually not a problem. Menstrual cycles aren't perfect and in my own practice, I typically tell clients not to worry about a single occurrence of any one particular issue because... things happen. Our cycles are considered "vital signs" because they do reflect our overall health and can be impacted by lots of things. And for the most part, our bodies make healthy adjustments to diet, stress, sickness, travel... you name it. We may feel that something is "off" for a little bit, but then things go back to normal.

If you're trying to postpone pregnancy, it's likely you wouldn't even notice the presence of a LUF at all. Your body will still be experiencing all the cyclical hormone changes just as if ovulation had occurred, because all the necessary elements are there. And for the purposes of avoiding pregnancy, it won't negatively impact the efficacy of your NFP method at all to have the egg be unreleased.

Where LUFs become problematic is when they start becoming more frequent and can actually be identified as a recurring syndrome. This is what the acronym LUFS stands for-- Luteinized Unruptured Follicle Syndrome.

It's a key factor in many instances of infertility, because obviously if your eggs are "trapped" inside the corpus luteum most cycles, they can't become fertilized.

How Do I Know if I'm Having LUFs?

By now, it should be fairly obvious that you can't really find LUFs in a basic NFP chart. Everything happens "according to plan" in the first half of the cycle and the follicle undergoes the process of luteinization-- so all of your hormones are going to look very similar to a cycle in which the egg is actually released. In some cases, LUFs might be suspected if the progesterone response looks weaker than normal, or if your luteal phase (the time after ovulation) is decreased a little bit (see: https://pubmed.ncbi.nlm.nih.gov/8671271/) But if you are regularly experiencing LUF's, you can't suss out a change in your charts because a lot of your charts will just look that way normally.

So the only real way to get this diagnosed is by serial ultrasound or even laparoscopic analysis.

But LUFs should be a part of the conversation with your doctor if you are experiencing infertility, especially in the presence of other conditions like endometriosis or PCOS, which are often associated with LUFS.

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