How does Family, Genes and Fertility are Related? An Easy Explanation:
Infertility is commonly defined as a couples’, who is in their reproductive age, inability to conceive after a year of regular, unprotected intercourse. This condition affects one in every six couples worldwide. Having a baby is a simple process for some couples. However, some couples face a lot of difficulties when it comes to natural conception. Nowadays, fertility struggle is one of the major concerns in our society, and the current generation is significantly affected by this.
Infertility is basically of two types: primary infertility, in which no previous pregnancies have happened; and secondary infertility, in which prior pregnancy has occurred but patient fails to conceive a second or a third time. There are several factors that hit couples with infertility such as: premature ovarian failure (POF), polycystic ovary syndrome (PCOS), endometriosis, advanced parental age, obesity, and hormonal imbalance, etc. Spermatogenesis is a disrupted sperm condition that caused primarily by male sterility, and is associated with abnormal semen (i.e., abnormal sperm count, morphology, or motility).
Apart from all these, one of the major factors that affects your fertility is your genetic makeup. Yes, it is absolutely true. The advancements in the field of genetics have proven the fact that our genes and chromosomes play a major and significant role in our fertility status. Our genetic information is packed into strings of DNA known as Chromosomes. The arrangement of genes and chromosomes in DNA depicts the genetic makeup of an individual. Any error/s in the early development of an egg, sperm, or embryo can lead to an abnormal number of chromosomes in the developing embryo.
The Different Levels In Which Genetics Influence Our Fertility.
Family History:
Genes strongly influence your fertility and the age of menopause in females. In fact, suppose if anyone in your family has experienced early menopause (mother, sister, or even your maternal grandmother), you are at double risk of having an early menopause. Sometimes, a person has all the genetic information and nothing is missing or duplicated. Still, they face infertility or miscarriages. In this case, it is important to evaluate the complete family history of both the partners so as to know the instances of late pregnancy or miscarriages. Reproduction and our gametes formation is under the control of multiple genes. Any issue at the genetic level can hamper the process and can result in reduced fertility or infertility.
For example, if your mother has one abnormal X chromosome, you are at 50% risk of inheriting that abnormal X which may result in conditions such as fragile X syndrome, or cystic fibrosis that can cause fertility issues.
Chromosomes.
Human cell has 46 chromosomes (22 pairs of autosomes and 1 pair of sex chromosomes – X and Y). A male chromosome complement is denoted as 46XY, while the female chromosome complement is 46XX. Parents share 50/50 chromosomes with their offspring. Any error in parental chromosome (i.e., missing or an extra pair of chromosomes), or any error in division of parental gametes at the time of embryo formation can lead to the aneuploidy risk in the baby.
The Impact of Parental Chromosome?
The parental genome makes a major contribution to the genome of the developing embryo. Most of the time, around 15-20% of recognized pregnancies end up as miscarriages, and in nearly 20% of cases, the underlying cause is at the genetic level. Nearly 50% of miscarriages in the early trimester are due to “Numerical Chromosomal Aneuploidy”. In such cases, parental chromosomal evaluation (Karyotype) is done. The karyotype is a simple blood test by which we get a snapshot of parental chromosomes. If a chromosome pair is missing, or an extra pair of chromosomes is added, or translocation (when a piece of one chromosome gets attached to another chromosome) happens, there is high risk of miscarriage. If any of the parent’s karyotype shows abnormality, PGT-A or Pre-implantation Genetic Testing of Embryos for Aneuploidy, is advised to look at the chromosomes in the embryos prior to implantation to reduce the rate of miscarriage due to aneuploidy.
Sometimes, in spite of a normal parental karyotype embryos attain an abnormal number of chromosomes from a parent due to the incorrect division of chromosomes at the time of gamete formation. This can be due to advanced maternal age, premature decreased ovarian reserve, high semen DFI and low sperm quality. PGT-A is advised to screen the embryos prior to transfer.
One of the major benefits of opting for IVF (In vitro-fertilization) is that couples can be tested for potential genetic problems prior to the start of the cycle. IVF is a medical procedure for assisting couples, who fails to conceive naturally or have some genetic problem at their chromosomal end, or has history of miscarriages, to get conceived. In this procedure female eggs are fertilized in the lab with the partner’s sperm and the embryos formed are first analyzed for their chromosomes. PGS is done on the embryos (day 5) formed by the IVF procedure.
Embryo Biopsy and Chromosomal Evaluation.
Once the fertilization (the fusing of egg and sperm) is done after IVF, the embryos are grown in the lab for up to 5 or 6 days. PGS is usually done on 5 days old embryos (blastocyst stage). Biopsy (6-8 cells) is performed on the sample taken from the trophectoderm layer and is tested in the genetic lab for the chromosomal count in the embryos using the novel genetic technique NGS or, Next-Generation Sequencing. Once the biopsy is taken, embryos are frozen in liquid nitrogen till the PGS report is due. Once the report is out, those embryos with the correct chromosomal count are selected and transferred to the patient. This transfer of frozen embryos is known as “frozen embryo transfer”. Transferring embryos with the correct number of chromosomes helps the patients to avoid miscarriage due to chromosomal aneuploidy and helps them take healthy babies home.
However, even today, not everyone is aware of the efficacy of such modern techniques. Couples should not hesitate to reach out and consult with their fertility specialists, for these experts can surely assist the ones who fight with their fertility issues or miscarriages for a very long time. In this era of advanced technologies, and along with the use of genetic techniques we can ensure enhanced and personalized fertility treatments for couples in need.
