Much of the conversation surrounding IVF focuses on eggs, sperm, and embryos. Yet even a chromosomally normal, high-quality embryo cannot establish a pregnancy without a receptive uterus. Implantation requires two elements working in synchrony: a competent embryo and a prepared endometrium. At New Hope IVF Hospital, evaluating and optimising the uterine environment is a core part of treatment planning, not an afterthought — because uterine factors are among the most correctable causes of implantation failure.
The Window of Implantation
The endometrium is receptive to an embryo for only a short interval, generally days six to ten after ovulation or the start of progesterone exposure. This is known as the window of implantation. Outside this window the endometrium either has not yet matured or has already begun to regress. Precise synchronisation between embryo stage and endometrial preparation is therefore essential, and it is one of the principal advantages of frozen embryo transfer, where timing can be controlled without the hormonal disruption of a stimulation cycle.
Endometrial Thickness and Pattern
Endometrial thickness is measured by transvaginal ultrasound before transfer. A thickness of at least seven millimetres with a trilaminar appearance is generally associated with favourable outcomes, though pregnancies do occur outside these parameters. A persistently thin endometrium may result from previous uterine surgery or infection, prolonged use of certain medications, or reduced blood flow. Management strategies include adjusting oestrogen route and dose, extending the preparation phase, vaginal sildenafil, granulocyte colony-stimulating factor, and treatment of any underlying adhesions.
Structural Conditions That Reduce Success
Several anatomical conditions can significantly impair implantation and are readily identified before transfer.
Submucosal fibroids, which distort the uterine cavity, reduce implantation and increase miscarriage rates; their removal restores outcomes toward normal. Endometrial polyps act as a mechanical barrier and produce local inflammation, and hysteroscopic polypectomy is a simple, effective remedy. Intrauterine adhesions following surgery or infection reduce the functional surface available for implantation. A uterine septum is associated with higher loss rates and is corrected hysteroscopically. Adenomyosis, in which endometrial tissue infiltrates the uterine muscle, impairs receptivity and may require a period of hormonal suppression before transfer.
Hydrosalpinx — a fluid-filled, blocked fallopian tube — deserves particular mention. The fluid can drain into the uterine cavity and is directly toxic to embryos, roughly halving IVF success rates. Surgical removal or occlusion of the affected tube before transfer restores success rates to expected levels and is strongly recommended.
Chronic Endometritis
Chronic endometritis is a persistent, low-grade inflammation of the endometrium that frequently produces no symptoms at all. It is identified on endometrial biopsy using specialised staining for plasma cells, and it is found in a notable proportion of patients with repeated implantation failure or recurrent loss. Treatment with a targeted course of antibiotics is simple and inexpensive, and resolution has been associated with improved implantation in subsequent cycles.
How We Assess and Prepare the Uterus
Assessment may include transvaginal and three-dimensional ultrasound, saline infusion sonography, and diagnostic hysteroscopy — which remains the reference standard for evaluating the uterine cavity and allows treatment at the same sitting. Where repeated implantation failure has occurred, endometrial biopsy for chronic endometritis and, in selected cases, endometrial receptivity testing to individualise transfer timing may be offered.
Preparation before transfer typically involves oestrogen to build the endometrium, followed by progesterone to induce receptivity, with ultrasound monitoring throughout. General health measures matter as well: controlled thyroid function, adequate vitamin D, a healthy weight, and avoidance of smoking all contribute to endometrial quality.
A Message to Patients
If you have experienced a failed transfer despite good-quality embryos, the uterine environment is one of the first places we look — and frequently one of the most fixable. Many of the conditions described here are corrected with a short day-case procedure or a course of medication, with meaningful improvement in the chance of success in the next cycle.
Our team at New Hope IVF Hospital in Sharjah is available to review your history and recommend the appropriate uterine assessment for your situation.