The Journey Of An Embryo, From Fertilisation To Implantation

Dr Sujatha Ramakrishnan Aug 23, 2024

Infertility is a growing concern worldwide, impacting 1 out of every 6 couples

Infertility is a growing concern worldwide, impacting 1 out of every 6 couples. Consequently, fertility treatments such as IVF have been gaining popularity and acceptance among the public. IVF has provided hope and joy to millions of couples struggling with infertility. However, there is still a great deal of confusion surrounding the IVF processes, steps and various stages involved in the overall treatment procedure.

The IVF Process and Timeline

IVF, or in vitro fertilisation, is a form of assisted reproductive technology (ART) where fertilisation occurs outside the human body. In this procedure, gametes (eggs and sperm) are collected from a couple and then fertilised in the lab. The resulting fertilised egg is transferred back into the uterus typically after 3-5 days of fertilisation. If the embryo successfully implants itself in the uterine wall, pregnancy occurs.

The commencement of an IVF cycle can vary and is typically scheduled based on the individual's menstrual cycles and other medical conditions. The cycle can start anywhere between 2 to 6 weeks from the initial consultation or decision to proceed with IVF.

In certain IVF protocols, oral contraceptives or other medications are prescribed for a period of 2 to 4 weeks before starting ovarian stimulation. This step is taken to regulate the menstrual cycle and prepare the ovaries for the upcoming stimulation process. On the other hand, in some cases, the ovarian stimulation phase begins immediately without the need for prior medications.

Ovarian Stimulation

Ovarian stimulation is a crucial stage in the In Vitro Fertilization (IVF) process, involving the intake of medications such as FSH (follicle-stimulating hormone) and sometimes LH (luteinising hormone). The purpose of this phase is to stimulate the ovaries so that the woman produces many mature eggs compared to the one or two eggs typically produced during a regular menstrual cycle. This phase holds significant importance as not all retrieved eggs may be mature, and not all mature eggs may successfully fertilise. Additionally, not every properly developed embryo that can be transferred leads to a successful pregnancy. Hence, initiating the process with a higher number of eggs increases the individual's chances of achieving conception during IVF.

Typically, an average of 10 to 15eggs are retrieved during the IVF process. The number of eggs produced and retrieved can be influenced by factors such as the patient's age, ovarian reserve, and the medical history of the patient. Your physician will tailor a specific protocol to maximise the number of eggs retrieved while also taking measures to prevent ovarian hyper-stimulation syndrome (OHSS). With the help of careful and frequent monitoring through hormonal testing and vaginal ultrasounds, this phase takes the aspiring parents one step closer to the joy of parenthood. Once an ultrasound determines the sufficient number of large enough follicles and estrogen level is at the right level for the individual, a trigger shot is induced for the final maturation of the eggs before retrieval.

Egg and Sperm Retrieval

Approximately 34 to 36 hours after taking the trigger shot, the egg retrieval procedure takes place. During this procedure, an ultrasound is used to provide visual guidance, and a small needle is inserted through the vaginal wall into the ovaries. Gentle suction is applied to remove the contents of the follicles, including the eggs, in the fluid. The collected fluid containing the eggs is then handed to an embryologist who meticulously examines it under a microscope to identify and retrieve the eggs. Detailed information about each egg is carefully recorded for further evaluation.

During the IVF process, the sperm is harvested from the male partner through ejaculation, in the form of semen collection. However, in situations where there are obstructions or difficulties with normal ejaculation, medical procedures can be used to extract sperm. In such cases, the sperm is retrieved directly from the epididymis or testes. For IVF procedures, fertility clinics generally prefer to work with fresh gametes (sperm and eggs) rather than frozen ones. Therefore, the male gamete retrieval typically occurs on the same day as fertilisation. This approach ensures that the retrieved sperm is at its best quality and maximises the chances of successful fertilisation.

Fertilisation

After the retrieval of eggs and sperm, the next step in the IVF process involves fertilising the eggs to form embryos. There are two main methods that can be used for fertilisation: conventional invitro fertilisation and intracytoplasmic sperm injection (ICSI).

In the conventional insemination method, the collected sperm is placed along with the eggs in a small petri dish. The eggs and sperm are then combined together in the laboratory, allowing the sperm to naturally enter the egg to fertilise it.

On the other hand, in the ICSI method, a single sperm is carefully injected directly into the cytoplasm of the egg using a delicate needle and an advanced operative microscope. This precise technique ensures fertilisation even if there are issues with sperm motility or other factors that could hinder natural fertilisation.

Both methods have proven successful in the fertilisation process, and the choice between conventional insemination and ICSI is made based on the specific circumstances and fertility challenges faced by the individual or couple undergoing IVF.

Embryo Transfer

After selecting the most viable embryo based on a grading system and then the embryo is transferred into the uterus within 1 to 2 months of the egg retrieval. To optimise the chances of success, the embryologist uses a careful evaluation process for each embryo. The embryo transfer process is a gentle procedure using a soft, flexible, and thin catheter to place the embryo into the uterus. During the transfer, an abdominal ultrasound is employed to ensure precise positioning, providing the best opportunity for the embryo to implant successfully.

Additional good quality embryos which are not utilised are often cryopreserved for future use, allowing for subsequent attempts or the possibility of expanding the family after a successful first cycle.

Charting a Course for the Future

Raising awareness about fertility issues and dispelling social stigma and misconceptions associated with it is the need of the hour. By fostering a more understanding and supportive environment, individuals and couples facing fertility challenges can feel less isolated and find emotional support during their journey.

Moreover, making fertility treatments, including IVF, more available, affordable, and accessible remains the end-goal. By ensuring that these treatments are within reach for a wider range of people, we can offer hope and possibilities for building families despite infertility challenges.