This is one of the most underleveraged conversations in fertility care. Most clinics have a standard pre-transfer checklist, and unless you ask specifically, the additional investigations that can meaningfully inform your protocol often don't get discussed. Here is what is worth knowing about.
The Uterine Environment
Saline Infusion Sonohysterogram (SIS) or Hysteroscopy
Before transferring an embryo, knowing the uterine cavity is clear of polyps, fibroids, or adhesions is fundamental. A standard ultrasound can miss small polyps that a saline sonohysterogram or hysteroscopy would catch. If you have not had a cavity check within the last twelve months, or if you have had a previous failed transfer, requesting a hysteroscopy rather than just a sonohysterogram gives the most direct view. Small polyps and minor adhesions can be removed at the same time.
Endometrial Thickness and Pattern
Your clinic will monitor this during your transfer cycle, but it is worth understanding what they are looking for. A trilaminar pattern, the three-layered appearance on ultrasound with a thickness of at least 7mm, and ideally above 8mm, is generally considered receptive. If your lining has historically been thin, it is worth having that conversation before the cycle starts rather than during it.
Endometrial Receptivity
ERA (Endometrial Receptivity Analysis): The ERA test analyses the genetic expression of your endometrial cells to determine your personal window of implantation the specific hours during which your endometrium is most receptive to an embryo. Most women fall within the standard window, but a meaningful percentage are displaced either pre-receptive or post-receptive meaning a standard transfer timing protocol is missing their window entirely.
The ERA requires a mock transfer cycle before your actual transfer. It is not cheap and it is not universally recommended for a first transfer in women with no previous failures. But for anyone with one or more failed transfers despite good embryos, it is one of the most clinically justified additional investigations available.
EMMA and ALICE Endometrial Microbiome
These tests, often run alongside the ERA from the same biopsy sample, assess the bacterial environment of the uterus. EMMA looks at the overall endometrial microbiome. ALICE tests specifically for chronic endometritis a low-grade infection of the uterine lining that causes no obvious symptoms but is associated with implantation failure and recurrent pregnancy loss.
Chronic endometritis is more common than most people realise estimates in women with recurrent implantation failure run as high as 30%. It is treatable with a targeted antibiotic course, but it requires testing to identify because it does not show up on standard swabs or blood tests.
Immune and Inflammatory Markers
This is the area where the evidence is most actively debated and where clinical practice varies most between centres. That is worth knowing upfront some of these tests are well established, others are used selectively, and the field is still developing.
Natural Killer Cell Testing
Uterine natural killer cells play a role in implantation and early placental development. Elevated peripheral blood NK cells have been associated with implantation failure and recurrent pregnancy loss in some research, though the relationship between blood NK levels and uterine NK activity is imperfect. Some reproductive immunologists use this as part of a broader immune panel to guide treatment decisions. It is not standard practice across all clinics and the protocols that follow from abnormal results typically intralipid infusions or steroids vary between centres.
Thrombophilia Screen
Clotting disorders both inherited and acquired can impair implantation and placental development. A basic thrombophilia screen covers factor V Leiden, prothrombin gene mutation, MTHFR variants, protein C and S, antithrombin III, and lupus anticoagulant. MTHFR in particular is relevant to folate metabolism and methylation, which connects back to the supplement conversation around methylfolate versus folic acid.
Antiphospholipid Antibodies
Antiphospholipid syndrome is an autoimmune condition that causes abnormal clotting and is associated with recurrent implantation failure and pregnancy loss. Testing for anticardiolipin antibodies and beta-2 glycoprotein antibodies is straightforward and the condition is treatable typically with low dose aspirin and low molecular weight heparin during a transfer cycle. It is worth requesting if you have had previous failures or losses and it has not already been investigated.
Thyroid Panel. Full, not just TSH
A TSH alone is not sufficient pre-transfer. The full panel TSH, free T4, free T3, and thyroid antibodies (TPO and thyroglobulin) gives a complete picture. The target TSH for a transfer cycle is generally considered to be below 2.5, and ideally closer to 1-2, which is more conservative than the broad normal range on a standard lab report. Elevated TPO antibodies indicate autoimmune thyroid disease which can affect implantation and early pregnancy even when TSH is currently normal.
Metabolic and Nutritional Markers
Ferritin and Full Iron Panel
As discussed in detail previously ferritin below 30 is suboptimal for fertility regardless of what the lab flags as normal. A full iron panel including ferritin, transferrin saturation, and haemoglobin is worth confirming before transfer, particularly if you have heavy periods, follow a plant-based diet, or have not had levels checked recently.
Vitamin D
Vitamin D receptors are present in the endometrium and play a role in immune modulation during implantation. Deficiency is common and easy to miss because it is not always included in standard pre-transfer bloods. The functional target for a transfer cycle is generally considered to be above 75 nmol/L, with some reproductive specialists aiming for 100-150 nmol/L. Correcting a significant deficiency takes several weeks of supplementation, which is another reason to test well before the transfer cycle rather than during it.
HbA1c and Fasting Insulin
If you have PCOS, a family history of diabetes, or any concern about insulin resistance, an HbA1c and fasting insulin test before transfer gives a picture of metabolic status that a random blood glucose does not capture. Insulin resistance affects endometrial receptivity and implantation, and identifying it before a transfer allows time to address it whether through dietary modification, inositol supplementation, or medication.
Sperm; Because it takes two
Sperm DNA Fragmentation
Standard semen analysis measures count, motility, and morphology. It does not measure DNA fragmentation damage to the genetic material inside the sperm that affects fertilisation, embryo quality, and development. Elevated sperm DNA fragmentation is one of the more common unidentified contributors to poor IVF outcomes and recurrent loss, and it does not necessarily correlate with a normal semen analysis. If your partner has not had sperm DNA fragmentation testing and you have experienced previous failed cycles or poor embryo development, this is worth requesting before the next transfer.
A Practical note on requesting these tests
Not all of these will be appropriate for every person or every situation. A first transfer in a straightforward cycle does not necessarily warrant the full list. But if you have experienced previous implantation failure, recurrent loss, or unexplained poor outcomes, most of these investigations are clinically justifiable and worth discussing directly with your consultant.
The key is to have the conversation before your cycle starts not mid-stimulation when there is limited time to act on the results. Book a dedicated review appointment, come with your questions written down, and ask specifically about each area rather than waiting for your clinic to raise them.
The best transfer is an informed one.
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