Fertilisation: From Gametogenesis to Birth

Fertilisation

The first phase in an organism’s sexual reproduction is gametogenesis, a process called meiosis allows haploid cells to be created from diploid parent cells. Gametogenesis is the formation of gametes which occurs from the germ cells in the testes and ovaries (Joseph, 2017). In a male, this process is termed spermatogenesis and oogenesis in a female. In a male, each primary cell or spermatocyte divides meiotically and produces four spermatids and then eventually become functional sperm cells (Abdullah, 2008). Comparably, of the four cells produced only one ultimately becomes a functional oocyte (Abdullah, 2008). This is illustrated in figure 1 displaying gametogenesis in humans.

Although about 300 million sperm enter the vagina, millions fall out or die from the acidic environment. However, many survive, and they move up through the cervix, into the uterus, and then to the end of the fallopian tube. If a single sperm can penetrate the egg, the egg will close off and Fertilisation occurs (Brown, 2013). Within the egg, the tightly packed male genetic material spreads out, a new membrane is created around the genetic material creating the pronucleus. Inside the membrane, the genes reform into the 23 chromosomes. The female genetic materials become activated by the fusion of the sperm with the egg resulting in the creation of the female pronucleus containing 23 chromosomes. Then microtubules pull the two of them together completing the process of fertilisation, at this moment a unique genetic code is created which instantly determines the baby’s features including its gender (Boyd, 2013). After the single-cell zygote is formed it begins to divide into a solid ball of cells, then, it becomes a hollow ball of cells called a blastocyst, attached to the lining of the uterus (Cherry, 2019). After the blastocyst stage, the major internal organs and external features begin to emerge, forming an embryo. In this stage the heart, spinal cord, and brain start to become visible (Khan academy, 2019). Once the formed features of the embryo begin to develop and grow it’s now considered a fetus. During this time specialization and differentiation of structures occur (Khan academy, 2019). Lastly, the baby is born after 9 months of pregnancy, this is shown in figure 2.

INFERTILITY

Infertility is a diminished or an absent ability to conceive and bear offspring naturally. Approximately, 10% of females are infertile and 7% male (Shiel, N.D.). Infertility is defined as not being able to conceive after 12 months of having unprotected sex. Infertility can have a wide variety of causes which are related to male and female or both. Treatment for infertility can include medications and assisted reproductive technologies (Shiel, N.D.). The most common forms of treatment are intrauterine insemination (IUI) and in vitro fertilisation (IVF) which are the most effective (Mayo Clinic, 2019).

Reason for Infertility (Males)

One reason for infertility in males is a varicocele. Most often, these occur after puberty and typically on the left side of the scrotum (Michigan Urology, 2019). Figure 3 depicts that a varicocele is an enlargement of the veins within the scrotum. As a result of a varicocele, it’s common to have low sperm production and decreased quality of the sperm. However, it can also lead to the testicle to fail to develop and shrink (Mayo clinic, 2016). The most common procedure to treat this problem is to undergo surgery to get it repaired.

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Reason for Infertility (Females)

A common reason for infertility in females is having structural problems in the reproductive system which is present in almost 8% of all women with infertility issues (Liu, 2014). Structural problems typically involve the presence of abnormal tissue in the fallopian tubes or uterus. If the fallopian tubes are blocked, the ovum are not able to move from the ovaries to the uterus and therefore the sperm won’t reach it resulting in no fertilisation (Boyden, 2017). Additionally, structural problems with the uterus, can interfere with implantation and cause infertility. Figure 5 shows a diagram of blockages in the female reproductive system.

IVF

In vitro fertilisation (IVF) is a procedure, used to overcome a range of fertility issues, by which the sperm and the egg are fused together outside of the body, in a specialized laboratory. The newly fertilised egg is grown in a protected environment for several days until being transferred into the uterus of the women during the blastocyst stage, therefore significantly increasing the chance of pregnancy (IVF Australia, 2019).

It has been suggested the Jan and Brian undergo the procedure of IVF using donor oocytes. This is because they are unable to naturally conceive, and they have had no eggs or sperm frozen.

ADVANTAGES OF USING IVF

• The biggest advantage of using IVF is the ability to have a successful and healthy baby. This applies to all couples with an infertility issue such as the women having blocked or damaged fallopian tubes, Ovarian failure, varicocele etc.
• Older patients with low ovarian reserve use IVF because it maximizes the chance of conceiving and focuses on the quality of the eggs.
• It can help single women or same sex couples if they wish to have a child.
• The embryos in the laboratory can be screened for inherited diseases. For individuals who are known carries of genetic diseases such as Huntington’s disease, cystic fibrosis and muscular dystrophy, IVF is the most reliable way to ensure that the child that is conceived will not suffer from a disorder.

DISADVANTAGES OF USING IVF

• There is a chance of developing multiple pregnancies. During IVF treatments there is usually more than one embryo being put back into the uterus. Around 25-30% of IVF pregnancies result in multiple pregnancies which increases the risk of miscarriages and infant problems (Create fertility, 2018).
• VF treatment is very expensive with the total price amounting around $12,000 to $15,000.
• IVF treatment is physically and emotionally demanding and if women over the age of 45 use IVF there is a chance of serious injury and in some cases death
• The highest percentage is below 50 both live birth rate and clinical pregnancy rate which is very low, considering all the disadvantages that come with the use of IVF.

Recommendation

It is strongly agreed that Jan and Brian should not undergo the IVF method. This is because the disadvantages severely outweigh the advantages. Firstly, because figure 6 shows that the live birth rate of a women 45+ years old using IVF is only a 2 – 3% success rate. Especially with the high costs they could be spending 10s of thousands of dollars on multiple trials with no reward. Additionally, because Jan is at an older age the physical toll that the procedure would take on her body would likely lead to her suffering from an illness, injury or even mortality. However, there is the slight chance that there is a successful pregnancy, through using donated eggs because of Jan’s ovarian deficiency and somehow having a successful live birth. Ultimately, it is up to Jan and Brian to decide whether they go through with the IVF procedure although, it is recommended that this would not be best for them.