What is Endometrial Preparation?
💡 Endometrial preparation transforms the uterine lining into an implantation-receptive state before embryo transfer. Target: trilaminar endometrium ≥7mm thickness. Methods include natural cycle, medicated (estrogen + progesterone), and modified natural cycle. The window of implantation opens 5 days after progesterone exposure for blastocysts.
Endometrial preparation is the clinical process of conditioning the uterine lining to achieve implantation receptivity before embryo transfer. It is achieved via the natural menstrual cycle or exogenous hormones, and its adequacy is assessed by transvaginal ultrasound before progesterone is commenced.
🇮🇳 India Context: Endometrial Preparation is widely assessed and treated across major Indian fertility centres including Chennai, Mumbai, Bangalore, Delhi, and Hyderabad.
What are the key characteristics of Endometrial Preparation?
- Goal: achieve endometrial thickness ≥7mm with trilaminar (triple-line) appearance on transvaginal ultrasound
- Trilaminar pattern indicates adequate estrogenic priming and glandular proliferation
- Two primary methods: natural cycle (endogenous hormones) and medicated cycle (exogenous estrogen + progesterone)
- Progesterone is the key hormone triggering secretory transformation — making the endometrium receptive
- Window of implantation (WOI): opens 5 days after ovulation (natural) or 5 days after progesterone start (medicated FET)
- Inadequate preparation (thickness <7mm or absent trilaminar pattern) results in cycle cancellation
- ERA test (endometrial receptivity array) used if repeated failed transfers suggest displaced window of implantation
- Endometrial thickness assessed at each cycle by transvaginal ultrasound before progesterone initiation
How does Endometrial Preparation work?
Why does Endometrial Preparation matter in fertility?
Endometrial preparation quality is a critical and modifiable determinant of embryo transfer success. A thin endometrium (<7mm) at time of transfer is associated with significantly lower implantation and clinical pregnancy rates — very few successful pregnancies are reported below 6mm. The trilaminar pattern signals adequate estrogenic priming of glands and stroma. Progesterone timing determines the window of implantation and must be precisely coordinated with embryo developmental stage. ERA testing identifies that 20–25% of women with recurrent implantation failure have a displaced window of implantation requiring personalised transfer timing.
What are related terms to Endometrial Preparation?
Medicated FET
Medicated FET is a frozen embryo transfer protocol using exogenous estrogen (tab…
Natural Cycle FET
Natural cycle FET is a frozen embryo transfer protocol in which the embryo is tr…
Progesterone
Progesterone is a hormone produced by the corpus luteum — the structure left in …
Embryo Transfer
Embryo Transfer is the final step of the IVF process. A laboratory-cultured embr…
FAQs about Endometrial Preparation
What is the minimum endometrial thickness for embryo transfer?
The minimum acceptable endometrial thickness for embryo transfer is generally 7mm with a trilaminar (triple-line) pattern. Most clinics target 8–12mm. Below 7mm, transfer is typically postponed. Very few successful pregnancies are reported with thickness below 6mm.
What is the trilaminar pattern on ultrasound?
The trilaminar (triple-line) pattern on transvaginal ultrasound shows three distinct bright lines in the endometrium — indicating adequate estrogenic priming and glandular proliferation. It is the most predictive ultrasound feature of endometrial receptivity before embryo transfer.
What causes thin endometrium for embryo transfer?
Thin endometrium (<7mm) is caused by: insufficient estrogen (low dose or poor absorption), uterine adhesions (Asherman's syndrome), prior uterine surgery, poor blood flow, or previous endometrial damage. Treatment options include increased estrogen dose, aspirin, sildenafil, or platelet-rich plasma.
What is the window of implantation?
The window of implantation is the 24–48 hour period when the endometrium is maximally receptive to embryo implantation — 5 days after ovulation (natural cycle) or 5 days after progesterone start (medicated FET). The ERA test identifies displaced windows in 20–25% of recurrent implantation failure cases.
What is ERA testing for endometrial preparation?
ERA (endometrial receptivity array) is a genetic test of a small endometrial biopsy that identifies the exact window of implantation. It is used when recurrent implantation failure is suspected to be due to a displaced window. Results guide personalised embryo transfer timing.
📚 Learn More
🏥 Find Specialists for Endometrial Preparation in India
Connect with verified fertility specialists who can guide you through endometrial preparation.