Genetic factors that influence fertility
It is important to understand that not only does your lifestyle and medical history play a role in your future baby’s health and wellbeing, but some family genes can also have an impact on your fertility and your pregnancy.
Common questions you can expect from your healthcare team during your preconception checkup include whether there is a family history of diabetes, high blood pressure, thyroid disease or chromosomal or genetic disorders such as Down Syndrome, cystic fibrosis, Tay-Sachs disease, muscular dystrophy or fragile X syndrome.
Have a conversation with your mum and female siblings about any pregnancy or labour complications they may have experienced. Research shows that children born to mothers who had pre-eclampsia (a condition that causes high blood pressure during pregnancy and after labour) may carry genes related to the condition.
Hoping for a multiple pregnancy? Fraternal twins can run in families so look for family trends of twin or triplets.
Genetic Conditions
Certain genetic conditions may affect fertility. In general, these genetic disorders or abnormalities fall into two categories: single gene defects and chromosomal abnormalities.
Single Gene Defects
Single gene defects are caused by DNA changes in one particular gene, and often have predictable inheritance patterns. Since only a single gene is involved, these disorders can be easily tracked through families and the risk of them occurring in later generations can be predicted. A single gene defect may cause a mutation or abnormality within the DNA. These can lead to conditions such as cystic fibrosis, Tay-Sachs disease, spinal muscular atrophy, sickle cell disease and Thalassemias.
Chromosomal Abnormalities
These abnormalities occur when a change in the number or structure of the chromosomes (which carry the DNA of the baby) happen. The normal number of chromosomes for humans is 46. Women have 22 pairs of autosomes and two X chromosomes while men have 22 pairs of autosomes and one X and one Y chromosome. Examples of chromosomal abnormalities include Klinefelter syndrome (an extra X chromosome is formed), Down syndrome (Trisomy 21, an extra chromosome 21) and Turner syndrome (loss of one X chromosome).
In men, chromosome abnormalities can at times be associated with low sperm counts. Genetic testing is recommended for all men with a low sperm count or a lack of sperm (medically referred to as azoospermia).
Depending on you and your family’s medical history, your healthcare team may suggest genetic tests for single gene defects as part of the initial preconception evaluation. Should a genetic or chromosomal abnormality be found during your evaluation, they may recommend genetic counselling in which a detailed family genetic history is obtained and an assessment of risk is determined.
