Breaking Barriers: The Evolution of In Vitro Fertilization Techniques

In Vitro Fertilization Techniques
May 8, 2024

Breaking Barriers: The Evolution of In Vitro Fertilization Techniques

In vitro fertilization (IVF), the process of fertilizing an egg with sperm outside the body has revolutionized the field of reproductive medicine. This groundbreaking technique, which led to the birth of Louise Brown, the first “test-tube baby” in 1978, has opened the doors for millions of families worldwide to experience the joy of parenthood.

IVF now accounts for a significant portion of births globally, with techniques like controlled ovarian stimulation, embryo culture, preimplantation genetic testing, and cryopreservation playing crucial roles in improving success rates and expanding the scope of what vitro fertilization means for infertility treatment.

Controlled Ovarian Stimulation

The Breakthrough of Controlled Ovarian Stimulation

Controlled ovarian stimulation (COS) emerged as a groundbreaking advancement in the 1980s, significantly boosting the average number of retrieved oocytes and pregnancy rates in in vitro fertilization (IVF) cycles. This technique involves the administration of exogenous gonadotrophins, co-treatment with gonadotropin-releasing hormone (GnRH) agonists or antagonists, and the triggering of final oocyte maturation to stimulate the development of multiple follicles.

Various gonadotrophin preparations, such as human menopausal gonadotrophin (hMG), purified follicle-stimulating hormone (p-FSH), highly purified FSH (hp-FSH), recombinant FSH (rFSH), and recombinant luteinizing hormone (rLH), are employed in COS protocols. Different GnRH agonist or antagonist protocols, including the long protocol, short protocol, and GnRH antagonists, are utilized to optimize the stimulation process.

  1. Ovarian Hyperstimulation Syndrome (OHSS): A Potential Complication 

    – OHSS is a severe complication associated with ovarian stimulation, characterized by symptoms ranging from mild abdominal distention to life-threatening conditions like renal failure.
    – Careful monitoring and adherence to protocols are crucial to mitigate the risk of OHSS during COS cycles.

  2. Optimizing Protocols for Improved Outcomes
Protocol Description
Long Luteal GnRH Agonist Involves the administration of GnRH agonists for pituitary desensitization before ovarian stimulation.
GnRH Antagonist Utilizes GnRH antagonists to prevent premature ovulation during ovarian stimulation.
Minimal Stimulation Employs lower doses of gonadotrophins for ovarian stimulation.

The primary objective of reviewing COS protocols is to assess their clinical effectiveness and safety profiles and generate a clinically valuable ranking to optimize outcomes for women undergoing IVF and intracytoplasmic sperm injection (ICSI) treatments.

In Vitro Fertilization and Embryo Culture

The Intricate Process of In Vitro Fertilization

In vitro fertilization (IVF) is a complex series of procedures aimed at treating infertility by facilitating fertilization outside the body. This groundbreaking technique involves a meticulous process of handling eggs, embryos, and sperm in a controlled laboratory environment.

  1. Oocyte Retrieval and Fertilization 

    – Mature oocytes (eggs) are retrieved from the ovaries using ultrasound-guided transvaginal aspiration.
    – These retrieved eggs are fertilized using conventional insemination or intracytoplasmic sperm injection (ICSI), where a single sperm is injected directly into the egg.

  2. Embryo Culture: A Delicate Balance 

    – Immediately after fertilization, the embryos are carefully cultured in specialized incubators that mimic the conditions of the female reproductive tract.
    – The embryos are closely monitored and cultured for two to five days, with the optimal duration determined through collaboration between the embryology lab and fertility specialist.

    Stage    Description
    Day 1-3 Embryos are typically cultured to the cleavage stage, where they divide into multiple cells.
    Day 5-6         Embryos can be cultured to the blastocyst stage, allowing for better selection and genetic testing.



  3. Optimizing Success Rates 

    – Advancements in embryo culture techniques have enabled the extension of in vitro culture to the blastocyst stage, facilitating better selection of embryos for transfer and preimplantation genetic testing. 

    – Approximately 80-90% of retrieved eggs are mature, with about two-thirds of mature eggs typically fertilizing and 80% developing into healthy blastocysts.

The in vitro fertilization process requires a dedicated team, including a physician, nurse, gynecological ultrasonography expert, and skilled embryology laboratory personnel, working together to maximize the chances of a successful pregnancy.

Preimplantation Genetic Testing

Preimplantation Genetic Testing: Enhancing Success and Reducing Risks

Preimplantation genetic testing (PGT) has emerged as a groundbreaking advancement in the in vitro fertilization (IVF) field. This technique allows for the identification of embryos affected by chromosomal imbalances or specific gene disorders before transfer to the uterus, significantly reducing the risk of transmitting genetic defects.

  1. Frozen Embryo Transfers (FETs) and Genetic Screening 

    – FETs enable genetic testing of embryos before implantation, resulting in higher success rates and a reduced chance of genetic defects or miscarriage. 

    – By identifying and transferring genetically healthy embryos, FETs increase the likelihood of a successful pregnancy and a healthy baby.

  2. Improved Success Rates with Frozen Embryos 

    – Studies suggest that frozen embryos are as effective as fresh ones, with improved success rates for frozen compared to fresh transfers. 

    – This improvement is primarily attributed to preimplantation genetic screening and the absence of residual retrieval hormones in the recipient’s body during FETs.

The integration of preimplantation genetic testing into IVF protocols has revolutionized the field, providing couples with the opportunity to maximize their chances of a successful pregnancy while minimizing the risk of genetic disorders in their offspring.

Embryo Transfer and Cryopreservation

The culmination of the in vitro fertilization (IVF) process lies in the embryo transfer and cryopreservation stages, where the journey toward parenthood reaches its pivotal moments.

Embryo Transfer: A Delicate Step Towards Conception

The embryo transfer procedure is a critical step in the IVF process. It involves implanting a fertilized embryo into the woman’s uterus with the guidance of a fertility doctor using ultrasound for precise placement. The timing is carefully determined, with embryos typically transferred at either the cleavage stage (Day 3) or the blastocyst stage (Day 5-6).

  1. Fresh Embryo Transfers (ETs): 

    Fresh ETs involve transferring newly created embryos back into the intended mother’s uterus three to five days after the initial egg retrieval. While Day 3 embryos are transferred to ensure their survival, Day 5 blastocysts have a higher chance of being genetically normal, leading to a successful live birth.

  2. Factors Influencing Transfer: 

    The number of embryos transferred depends on the recipient’s age and reproductive history. In many cases, fertility specialists may opt to transfer only one embryo into the uterus. Still, sometimes, two embryos are transferred to increase the chances of successful implantation for women aged 35 or older.

Cryopreservation: Preserving Hope for the Future

Cryopreservation, or freezing, of embryos has become integral to IVF. Excess good-quality embryos not transferred during the initial cycle are cryopreserved for future use, offering couples additional opportunities for pregnancy without undergoing a new egg retrieval cycle.

Aspect Frozen Embryo Transfer
Timing It can be done in weeks, months, or even years after the initial egg retrieval
Success Rates Improved cryopreservation techniques have made frozen transfers equally successful, if not more, than fresh transfers
Cost Typically ranges from $3,000 to $10,000, sometimes separate from the IVF package

Frozen embryo transfers offer several advantages, including the ability to optimize the uterine environment for implantation and the opportunity for preimplantation genetic testing to identify genetically healthy embryos. Additionally, thawed frozen embryos can be implanted either in the patient or in another person, with similar or higher pregnancy rates than with fresh embryos.


  1. How has in vitro fertilization (IVF) evolved since its inception? 

    In vitro fertilization (IVF) has seen significant advancements since the birth of the first IVF baby in 1978. Initially, the success rates were relatively low, but today, the procedure achieves nearly a 50% success rate in cases involving women under 35.

  2. Can IVF influence human evolution? 

    IVF may impact human evolution. According to Dr. Hans Hanevik, who heads the fertility department at Telemark Hospital in Norway, IVF could allow genes that might otherwise not be passed on due to the carrier’s death to be transmitted to future generations. This could alter the human genome. 

  3. What are the steps involved in the IVF process?

The IVF process involves several key steps:

– Eggs are extracted from follicles within an ovary.

– These eggs are injected with a single sperm or mixed with sperm in a petri dish to facilitate fertilization.

– The resulting embryo is subsequently transferred into the uterus for potential implantation.