IVF Explained: Why Embryo Quality Alone Isn’t Enough For Pregnancy

For couples undergoing IVF, few moments are as reassuring as hearing that a “good-quality” embryo has been transferred. In vitro fertilisation (IVF) brings hope to millions of couples trying to conceive, but it can also be confusing when a “good” embryo does not result in pregnancy. To understand this better, we spoke to Dr Mohammed Ashraf C, Scientific Director & Head of Embryology, Milann - Fertility & Birthing Hospital, Bengaluru, for insights on why embryo quality alone cannot guarantee IVF success:

What Is A ‘Good’ Embryo?

In IVF, embryos are graded based on their appearance under the microscope, including cell number, symmetry, fragmentation, and rate of development. “At the blastocyst stage, grading also considers the inner cell mass and trophectoderm quality. A high-grade embryo statistically has a better chance of implantation compared to a poor-grade one,” explains Dr Mohammed Ashraf. Even a visually perfect embryo may carry chromosomal abnormalities that prevent implantation or cause early miscarriage.

Three major elements determine success:

• Chromosomal integrity

• Uterine receptivity

• Right timing

Role of Chromosomes In IVF Success

Each embryo should contain 46 chromosomes: 23 from the egg and 23 from the sperm. During early cell division, DNA must be accurately copied and equally distributed.

“If errors occur during this process, chromosomal abnormalities (aneuploidy) may arise. Chromosomal errors increase with maternal age and can originate from the egg, sperm, or both. Even visually perfect embryos may be genetically abnormal”, says Dr Mohammed Ashraf.

Preimplantation Genetic Testing (PGT) can identify embryos with the correct chromosomal number (euploid embryos), which have a significantly higher implantation potential. “PGT is individualised and recommended based on age, history, and clinical indications,” adds Dr Ashraf.

Importance of Uterine Receptivity

Implantation is a highly coordinated dialogue between the embryo and the endometrium. “Even the best embryo cannot implant if the uterine environment is not receptive,” explains Dr Ashraf.

Factors that may interfere include:

• Thin endometrial lining

• Fibroids or polyps

• Intrauterine adhesions

• Chronic endometrial inflammation

• Altered blood flow

• Hormonal imbalance, especially progesterone

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Timing Matters: The Window of Implantation

“The ‘window of implantation’ is a brief, hormonally regulated period when the uterine lining is optimally prepared to accept an embryo,” says Dr Ashraf. If embryo transfer occurs too early or too late, implantation may fail, even if both embryo and uterus are otherwise healthy. Precision in hormonal preparation and synchronisation is therefore critical.

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Health And Lifestyle Factors

Reproductive success is also influenced by overall health. Thyroid disorders, uncontrolled diabetes, obesity, autoimmune conditions, and nutritional deficiencies can reduce implantation potential. Lifestyle factors such as smoking, excess alcohol, caffeine, and chronic stress also impact outcomes. “Optimising metabolic and hormonal health improves the environment in which implantation occurs. One of the most common reasons IVF cycles fail is chromosomal error during early embryonic DNA replication. This explains why multiple attempts are sometimes necessary”, notes Dr Mohammed Ashraf.

Successful fertility treatment goes beyond the embryo - it requires the perfect alignment of science, patience, timing, and personalised care.

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Image credit: Freepik