Fertility / Gynaecology · Endometrium
Endometrial Thickness — Cycle & Fertility
Womb lining thickness changes through cycle (2-4 mm post-period to ~12 mm peak). Trilaminar ≥7 mm ideal for implantation. Postmenopausal bleeding + >4 mm needs biopsy (endometrial cancer rule-out).
Last reviewed 2 June 2026
Endometrial thickness for IVF transfer
Liu 2018 — outcome bands for transfer
Cycle type
Endometrial pattern on TVUS
Educational tool only — not medical advice. Liu 2018 (Hum Reprod) analysed > 40,000 transfers and showed a clear threshold effect at 7 mm with continued improvement up to ~8–9 mm and a plateau thereafter. ESHRE Recurrent Implantation Failure Guideline 2023 endorses individualised cut-offs. Your fertility specialist will integrate thickness with pattern, prior history, embryo quality, and patient preference.
What does this mean?
The endometrial lining needs to be both thick enough and structurally receptive for an embryo to implant. The Liu 2018 analysis of > 40,000 IVF transfers gave us our best modern data: live-birth rate rises sharply between 6 and 8 mm, then plateaus across the “optimal” 8–13 mm range, with no clear additional benefit above that. Triple- line (trilaminar) pattern on TVUS is the receptive pattern; homogeneous after progesterone is expected, but homogeneous BEFORE progesterone signals suboptimal estrogenisation. If thin, options to thicken include: extended-duration estradiol, vaginal estradiol, pentoxifylline + vitamin E, hCG priming, intrauterine G-CSF, and intrauterine autologous PRP — evidence is moderate and varies by protocol. If unexpectedly thick (especially with abnormal bleeding), rule out hyperplasia or polyps with hysteroscopy before transfer. The clinical decision balances lining thickness against embryo quality, time pressure, treatment burden, and prior cycle history.
What is endometrial thickness?
Measurement of womb lining on transvaginal ultrasound. Changes through menstrual cycle: 2-4 mm post-period → ~9-13 mm around ovulation. Context (cycle day, menopausal status) matters.
Normal thickness
- Fertility / implantation: trilaminar + ≥7 mm ideal.
- Postmenopausal: ≤4 mm reassuring; >4 mm + bleeding needs evaluation.
- Cycling: early follicular 4-8 mm; ovulation 8-13 mm; secretory >12 mm; menstrual <4 mm.
Triple-line / trilaminar pattern
Three lines on ultrasound around ovulation; reflects optimal proliferation. Associated with better implantation rates. Uniformly bright (echogenic) pattern: lower fertility outcomes.
Thin endometrium causes
- Asherman’s syndrome (intrauterine adhesions).
- Previous endometrial damage (D&C, ablation).
- Chronic endometritis (infection).
- Estrogen insufficiency.
- Radiation exposure.
- Poor uterine blood flow.
Thin endometrium treatments
- Higher-dose estrogen.
- Vaginal sildenafil (mixed evidence).
- Hysteroscopy + adhesion release (Asherman’s).
- PRP injection (experimental).
- Growth hormone (research).
Postmenopausal bleeding — never normal
Same-week GP appointment. Workup:
- Transvaginal ultrasound for endometrial thickness.
- ≤4 mm: low risk; investigate further if persistent.
- >4 mm: endometrial biopsy (rule out cancer; 5-10% PMB chance).
- >12 mm: usually direct biopsy.
Stage 1 endometrial cancer ~90% 5-year survival when caught early.
Endometrial polyps
Benign growths. ~24% of women at some point. Symptoms: irregular bleeding, post-coital, heavy periods, PMB, fertility issues. Treatment: hysteroscopic removal if symptomatic / >1.5 cm / postmenopausal.
Asherman’s syndrome
Intrauterine adhesions from D&C / surgery / infection. Light or absent periods, recurrent miscarriage, infertility, cyclical pain, thin endometrium.
Hysteroscopic adhesiolysis — many regain fertility.
Endometrial cancer risk factors
- Obesity (commonest).
- Nulliparity.
- Late menopause.
- Early menarche.
- Diabetes.
- Tamoxifen.
- Lynch syndrome.
- PCOS.
Peak age 60-70s. Incidence rising due to obesity. No routine screening in general population.
IVF + endometrium
- Trilaminar + ≥7-8 mm before embryo transfer ideal.
- <7 mm: lower implantation rates.
- >14 mm: also reduced.
- Estrogen support; cycle adjustment; freeze + try again.
Different scenarios
Scenario 1: 55 yo, post-menopausal bleeding, thickness 8 mm
Endometrial biopsy. Cancer ruled out usually, but essential workup.
Scenario 2: IVF cycle, day 12 endometrium 5 mm
Thin. Estrogen support; consider freezing embryos for better cycle.
Scenario 3: Asherman’s after D&C, planning fertility
Hysteroscopic adhesiolysis. Estrogen post-op. Recheck thickness next cycle.
Scenario 4: PCOS, irregular cycles, thickening on US
Endometrial protection important — progestogen / combined pill / mirena until pregnancy.
Scenario 5: Polyp incidentally found, asymptomatic
Discuss removal if >1.5 cm or postmenopausal. Small + asymptomatic: observe.
Care guidance — endometrium
- Postmenopausal bleeding: never ignore.
- Trilaminar ≥7 mm ideal for implantation.
- Healthy lifestyle supports endometrium.
- PCOS women: progestogen protection against thickening.
- Asherman’s: surgical treatment + estrogen.
- Fertility specialist for persistent thin endometrium.
Sources
- NICE NG12. Suspected cancer: recognition and referral.
- RCOG Green-top 67. Management of postmenopausal bleeding.
- NICE NG88. Heavy menstrual bleeding.
- ASRM. Endometrium and fertility.
Recommended for this calculator
Frequently asked questions
What is endometrial thickness?
MEASUREMENT of the womb LINING (endometrium) on transvaginal ultrasound. CHANGES through menstrual cycle: thin after period (~2-4 mm); thickens through follicular phase (estrogen-driven); peaks ~9-13 mm at ovulation; further thickens in luteal phase (progesterone) for possible pregnancy; sheds as period if no pregnancy. CONTEXT MATTERS: cycle day, pre/postmenopausal status, fertility/IVF context determines interpretation.
What's the normal endometrial thickness?
FERTILITY context (timed to ovulation/embryo transfer): TRILAMINAR (3-layered) pattern + thickness ≥7 mm IDEAL for implantation. <7 mm = THIN ENDOMETRIUM (concerning). POSTMENOPAUSAL: ≤4 mm reassuring; >4 mm + bleeding needs evaluation. CYCLING WOMAN: varies by day — early follicular 4-8 mm; ovulation 8-13 mm; secretory >12 mm; menstrual <4 mm.
When is it measured?
(1) FERTILITY ASSESSMENT: cycle day 10-14 (ovulation timing) for natural fertility planning; embryo transfer cycles in IVF — usually 12+ days from start of stimulation. (2) POSTMENOPAUSAL BLEEDING workup: any post-menopausal bleeding; ≥4 mm needs investigation for endometrial cancer. (3) ABNORMAL BLEEDING in pre-menopausal women. (4) HRT MONITORING (rare). (5) POLYCYSTIC OVARIAN syndrome assessment.
What if my endometrium is thin?
THIN ENDOMETRIUM (<7 mm in fertility context) — concerning for implantation. CAUSES: (1) ASHERMAN'S SYNDROME (intrauterine adhesions from previous surgery/infection); (2) PREVIOUS endometrial damage (D&C, ablation); (3) CHRONIC ENDOMETRITIS (infection); (4) ESTROGEN insufficiency; (5) RADIATION exposure; (6) POOR blood flow (uterine artery). TREATMENTS: (1) higher-dose estrogen; (2) vaginal sildenafil (Viagra) — improves blood flow; mixed evidence; (3) hysteroscopy + adhesion release (Asherman's); (4) PRP (platelet-rich plasma) injection — experimental; (5) GROWTH HORMONE — research level. SPECIALIST guidance.
What's a triple-line / trilaminar pattern?
DESIRABLE pattern around OVULATION + before EMBRYO TRANSFER. THREE LINES visible on ultrasound: bright hyperechoic outer line (basal endometrium), dark hypoechoic middle line (functional layer), bright hyperechoic inner line (cavity). REFLECTS optimal proliferation + estrogen exposure. ASSOCIATED with better implantation rates. ABSENT or 'echogenic' (uniformly bright) patterns associated with lower fertility outcomes.
Postmenopausal bleeding — what should I do?
ANY postmenopausal bleeding NEEDS EVALUATION — never normal. SAME-WEEK appointment with GP. WORKUP: transvaginal ultrasound + endometrial thickness assessment. (1) ≤4 MM: low risk; investigate symptoms further. (2) >4 MM: ENDOMETRIAL BIOPSY (hysteroscopy + curettage or aspiration) — rule out endometrial cancer (5-10% chance with PMB). (3) >12 MM: usually proceed direct to biopsy. (4) ULTRASOUND ABNORMAL features (polyps, irregular): hysteroscopy. PREVENTION: report bleeding early. PROGNOSIS for endometrial cancer good when caught early (Stage 1: ~90% 5-yr survival).
What's endometrial polyp?
BENIGN GROWTH on uterine lining. AFFECT ~24% of women at some point. SYMPTOMS: irregular bleeding, post-coital bleeding, heavy periods, postmenopausal bleeding, sometimes fertility issues. DIAGNOSIS: ultrasound + saline infusion sonography (SIS) or hysteroscopy. TREATMENT: REMOVAL via hysteroscopy if symptomatic / >1.5 cm / postmenopausal (small cancer risk in this group). SMALL ASYMPTOMATIC: may resolve spontaneously; observation. FERTILITY: polyp removal sometimes improves outcomes.
What about fibroids and endometrial thickness?
FIBROIDS (uterine myomas) can affect: (1) MEASUREMENT — distort cavity making accurate measurement difficult; (2) APPEARANCE — submucosal fibroids protrude into cavity. FIBROIDS associated with: heavy periods, pelvic pain, fertility issues (submucosal especially). DIAGNOSIS: ultrasound + sometimes MRI + saline sonography or hysteroscopy. TREATMENT: depends on size + location + symptoms + fertility plans; medication, hysteroscopic resection, myomectomy, UAE (uterine artery embolisation), GnRH agonists, hysterectomy. /calculators/recurrent-miscarriage (fibroid context).
Endometrial cancer signs?
MOST COMMON: postmenopausal bleeding (any amount; brown, red, spotting). PRE-MENOPAUSAL: heavy / irregular bleeding, bleeding between periods. RARE in young women but possible (lynch syndrome risk; PCOS risk). PROTECTIVE: combined oral contraceptive, multiparity, breastfeeding, normal weight. RISK FACTORS: obesity (commonest), nulliparity, late menopause, early menarche, diabetes, tamoxifen, lynch syndrome, PCOS. AGE: peak 60-70s. INCIDENCE rising in UK due to obesity. SCREENING not routine in general population.
How does this affect IVF?
IVF success linked to endometrial thickness + pattern. (1) IDEAL: trilaminar + ≥7-8 mm before embryo transfer. (2) <7 MM: lower implantation rates. (3) >14 MM: also reduced rates (over-development). MANAGEMENT: estrogen support; cycle adjustment; freeze embryos + try better cycle; specialist intervention for thin endometrium. EVERY IVF clinic monitors closely.
What about Asherman's syndrome?
INTRAUTERINE ADHESIONS (scar tissue inside uterus) — most often from D&C / surgery / severe pelvic infection. CAUSES: (1) Light or absent periods; (2) Recurrent pregnancy loss; (3) Infertility; (4) Cyclical pain (blood trapped); (5) Thin endometrium. DIAGNOSIS: hysteroscopy gold standard; SIS; MRI. TREATMENT: hysteroscopic adhesiolysis (cutting adhesions). PROGNOSIS: depends on severity; many regain fertility. PREVENTION: gentler surgical approaches; oxytocin not D&C for retained placenta when possible.
Endometrial thickness for trying naturally?
OPTIMAL: ≥7-8 mm trilaminar around ovulation. IF SHORTER consistently — see GP / fertility specialist. NOT routinely checked unless infertility workup. NATURAL FERTILITY: tracking ovulation + timing intercourse (every 1-2 days fertile window) more practical for most. UNUSUAL cycles / suspected anatomical issue: ultrasound + cycle tracking.
Does diet / lifestyle affect endometrium?
(1) GENERAL HEALTH supports: balanced nutrition; healthy weight (extremes affect cycle + endometrium); regular exercise; sleep. (2) STOP SMOKING (reduces blood flow, harms endometrium). (3) MODERATE alcohol. (4) DIABETES control (glucose control important). (5) VITAMIN E + L-arginine — some evidence for endometrial support; modest. (6) ANTIOXIDANTS general. (7) STRESS REDUCTION. NO SPECIFIC FOOD proven to dramatically thicken; healthy lifestyle is foundation.
How does this relate to other calculators on BumpBites?
Companion: /calculators/luteal-phase; /calculators/ovulation; /calculators/fertility-window; /calculators/recurrent-miscarriage; /calculators/pcos-pregnancy; /calculators/semen-analysis (partner); /calculators/fertility-tracking-accuracy.