Glossary

Cycle day

Counted from the first day of full bleeding, which is always cycle day 1. Spotting the day before doesn't count — the count starts when proper bleeding does.

Peak day

The last day you notice the most fertile-quality mucus — clear, stretchy, or slippery. You can only identify it looking backwards, once the mucus has dried up. Ovulation usually happens within a day either side, which is why almost everything in Filia is timed from it.

Pre-Peak

The first half of your cycle, from your period until Peak day. Estrogen is rising and a follicle is maturing. Also called the follicular phase.

Post-Peak

The second half of your cycle, from the day after Peak until your next period starts. Progesterone is high. Also called the luteal phase. A healthy one runs 12–16 days.

Follicular phase

The medical name for Pre-Peak — the first half of your cycle, named after the follicle developing in your ovary.

Luteal phase

The medical name for Post-Peak — the second half of your cycle. Named after the corpus luteum, the structure left behind after the egg is released.

P+7

Peak day plus seven. The single most useful day to test progesterone, because that's when it should be at its highest. "P+3" means three days after Peak, and so on.

BBT

Basal body temperature — your temperature at complete rest, taken first thing before you sit up, drink, or speak. It rises slightly after ovulation and stays up.

Thermal shift

The small rise in waking temperature — usually 0.4–0.6°F — that happens after ovulation because progesterone raises your body's thermostat. Seeing it confirms ovulation actually occurred.

Biphasic

A temperature chart with two clear levels: lower before ovulation, higher after. That two-level shape is what a healthy ovulatory cycle looks like.

Coverline

A line drawn on your chart just above the highest of the six low temperatures before your shift. Three temperatures above it confirms ovulation happened.

Cervical mucus

Fluid produced by the cervix that changes across your cycle in response to estrogen. It goes from dry, to sticky, to stretchy and clear like raw egg white. It's the most reliable day-to-day sign of fertility, and fertile-quality mucus keeps sperm alive for several days.

Tail-end brown bleeding

Brown spotting at the very end of your period, often shortened to TEBB. A day or two is common. More than that can point to low progesterone or endometriosis, which is why Filia tracks it separately.

Anovulation

A cycle where no egg is released. You can still bleed without ovulating, which is why bleeding alone doesn't confirm a normal cycle.

Fertile window

The days when sex could result in pregnancy — roughly the five days before ovulation plus the day of. Sperm survive in fertile mucus, which is why the window opens before ovulation rather than on the day.

Estrogen / Estradiol (E2)

The main estrogen. It builds your uterine lining and produces fertile mucus in the first half of your cycle. "E2" is shorthand for estradiol, the form measured in blood tests.

Progesterone

The hormone produced after ovulation that maintains your uterine lining and supports early pregnancy. Low progesterone is one of the most common and most treatable fertility problems.

FSH

Follicle-stimulating hormone. It tells your ovaries to start maturing an egg each cycle. Measured on cycle day 3 as a rough gauge of ovarian reserve — a high result can suggest your ovaries are working harder than expected.

LH

Luteinizing hormone. It surges 24–36 hours before ovulation, which is what ovulation predictor strips detect.

AMH

Anti-Müllerian hormone. Reflects roughly how many eggs you have left. It's stable across the cycle so it can be drawn any day. Important: it says nothing about egg quality, and it's suppressed while on hormonal birth control.

Prolactin

The hormone that drives milk production. When it's raised outside of breastfeeding it can suppress ovulation entirely.

Testosterone (total and free)

Women make testosterone too, in small amounts. "Total" is everything in your blood; "free" is the portion actually available to your cells. Raised levels are a common feature of PCOS.

SHBG

Sex hormone binding globulin — a protein that grabs onto testosterone and estrogen and holds them inactive. Low SHBG means more free hormone circulating, and it's closely tied to insulin resistance.

DHEA-S

A hormone made by your adrenal glands that your body converts into other sex hormones. Raised levels point toward an adrenal contribution to PCOS.

17-OHP

17-hydroxyprogesterone. Screens for a treatable inherited condition (non-classic congenital adrenal hyperplasia) that can look like PCOS but is managed differently.

TSH

Thyroid stimulating hormone. Counterintuitively, a high TSH means an underactive thyroid — it's your brain shouting louder at a gland that isn't responding. Standard labs call up to 4.5 normal, but under 2.5 is the target when trying to conceive.

Free T4 and Free T3

The actual thyroid hormones. T4 is the storage form; T3 is the active one your body uses. Normal T4 with low T3 suggests a conversion problem rather than a thyroid failure.

Reverse T3

An inactive form of thyroid hormone your body makes more of under stress, illness, or under-eating. Its usefulness is debated among specialists.

TPO antibodies

Antibodies that attack your thyroid. Their presence means your immune system is involved — the hallmark of Hashimoto's — and raises miscarriage risk even when TSH looks normal.

hCG

The hormone a pregnancy produces, and what a pregnancy test detects. Also given as an injection in some treatments to trigger ovulation.

PCOS

Polycystic ovary syndrome. Despite the name it isn't really about cysts — it's a hormonal and metabolic condition where ovulation becomes irregular or stops. Insulin resistance drives most cases, which is why diet and metabolic treatment often work.

Endometriosis

Tissue similar to your uterine lining growing outside the uterus, causing pain and inflammation. Diagnosis is delayed by 7–10 years on average, which is why cycle patterns matter for catching it earlier.

Luteal phase deficiency

When the second half of your cycle is too short (under about 10–11 days) or progesterone is too low to sustain a pregnancy. Common, detectable from charting, and usually treatable.

Functional hypothalamic amenorrhea

Periods stopping because of under-eating, over-exercising or sustained stress — your brain switches off the reproductive signal to conserve energy. Often mistaken for PCOS, which matters enormously because the treatment is the opposite: eat more, train less.

Subclinical hypothyroidism

A mildly underactive thyroid — TSH is raised but the actual thyroid hormones still look normal. Easy to dismiss, but it measurably affects fertility and miscarriage risk.

Hashimoto's

An autoimmune condition where your immune system gradually attacks your thyroid. The most common cause of an underactive thyroid, identified by TPO antibodies.

Insulin resistance

When your cells stop responding well to insulin, so your body makes more of it. High insulin disrupts ovulation directly. It shows up in blood years before blood sugar rises, which is why fasting insulin is worth measuring.

Diminished ovarian reserve

Fewer eggs remaining than expected for your age. Suggested by low AMH or raised day-3 FSH. It affects how much time you have, not whether you can conceive now.

Recurrent pregnancy loss

Two or more consecutive miscarriages. It warrants a proper investigation rather than being told to keep trying — several causes are identifiable and treatable.

Chronic endometritis

Persistent low-grade inflammation of the uterine lining, usually with no symptoms at all. Linked to repeated implantation failure and miscarriage, and treatable with antibiotics once found.

Bacterial vaginosis

An imbalance where protective Lactobacillus bacteria are crowded out by others. Often has no symptoms, recurs in 50–80% of cases after antibiotics, and is linked to preterm birth.

Unexplained infertility

A label meaning standard tests found nothing — which frequently means "incompletely investigated" rather than "nothing wrong". Luteal deficiency, thyroid problems and insulin resistance are routinely missed by standard workups.

Reference range

The range your lab prints as "normal". It's the middle 95% of everyone they tested — including people who are unwell. Being inside it means you're statistically ordinary, not necessarily optimal.

Fertility-optimal range

A narrower target drawn from fertility research rather than population averages. Filia shows these alongside your lab's range. They are educational context for a conversation with your provider, not a diagnosis.

Fasting

Nothing but water for 12 hours before the draw. Coffee, tea and gum all count as breaking it. Required for insulin, glucose and several nutrient markers.

Requisition

The order form a lab needs before it will draw your blood. Filia can give you one to take to any lab or your own provider.

Ferritin

Your stored iron. Symptoms of low iron appear well before anemia shows up on a blood count, and standard labs set the floor far too low — under 50 is worth addressing even if you're told it's normal.

hs-CRP

High-sensitivity C-reactive protein — a measure of low-grade inflammation throughout your body. The "high-sensitivity" version detects the small elevations that matter for fertility.

HOMA-IR

A number calculated from your fasting glucose and insulin that estimates insulin resistance. No extra blood needed — it's arithmetic on results you already have.

HbA1c

Your average blood sugar over roughly the last three months, so a single bad week doesn't distort it.

Homocysteine

An amino acid that rises when your body isn't processing B vitamins well. Raised levels are linked to miscarriage and often improve with the right form of folate.

MTHFR

A gene affecting how well you convert folate into its usable form. Common variants reduce that conversion, which is why some people are advised to take methylfolate rather than folic acid.

Immunoassay

The standard, inexpensive method most blood tests use. Accurate across normal ranges, less reliable at very low concentrations.

LC-MS/MS

A more precise laboratory method used when accuracy at very low levels matters — for example measuring estrogen in men, or in women taking medication that suppresses it.

Serial testing

Repeating the same test at several points instead of once, to see a curve rather than a snapshot. Used for progesterone across the luteal phase.

Restorative reproductive medicine

An approach that looks for the specific cause of a fertility problem and treats it, rather than moving straight to bypassing it. Filia is built on this idea.

NaProTECHNOLOGY

A structured medical system that uses standardized cycle charting to diagnose and treat underlying causes of infertility. Much of the charting logic in Filia comes from this research.

Ovulation induction

Medication such as letrozole or clomiphene used to prompt ovulation in someone who isn't ovulating reliably.

Letrozole

A tablet that temporarily lowers estrogen, prompting your body to mature and release an egg. Now considered first-line for PCOS ahead of clomiphene.

Luteal support

Progesterone given after ovulation to strengthen the second half of the cycle, usually when charting or a P+7 result shows it's short or low.

ART / IVF / IUI

Assisted reproductive technology. IUI places prepared sperm directly into the uterus; IVF fertilises eggs outside the body and transfers an embryo back. Both bypass a problem rather than treating its cause — sometimes exactly the right choice.

Microbiome

The community of bacteria living in and on you. There are distinct ones in your gut, vagina and uterus, and which species dominate genuinely affects your health.

Lactobacillus

The protective bacteria that should dominate a healthy vagina. They keep it acidic, which discourages other organisms. L. crispatus specifically is linked to better implantation rates.

Dysbiosis

An imbalanced microbial community — the protective species have been crowded out by others. The underlying problem in bacterial vaginosis.

Biofilm

A protective layer bacteria build around themselves that antibiotics struggle to penetrate. It's the main reason bacterial vaginosis keeps returning after treatment.

Estrobolome

The gut bacteria that recycle estrogen back into your bloodstream. A real mechanism, though commercial tests claiming to measure it are less reliable than the marketing suggests.

Randomized controlled trial

A study where participants are randomly assigned to treatment or comparison groups. Randomization is what allows a study to show cause rather than just association. Often shortened to RCT.

Meta-analysis

A study that pools results from many earlier studies to reach a more reliable conclusion than any single one could.

Systematic review

A structured search of all research on a question, using pre-set rules so the authors can't cherry-pick the studies that suit them.

Cohort study

Following a group over time and observing what happens. Useful and often large, but can't prove cause the way a randomized trial can.

Odds ratio / relative risk

Ways of expressing how much something changes your chances. An odds ratio of 2.0 roughly means double the odds. Always worth asking: double of what starting number?

Evidence grade (A / B / C)

Filia's rating of how solid the evidence is. A — multiple good trials agree. B — smaller or observational studies. C — early or preliminary. The grade is shown so you can weigh things yourself.