Blood Related, Will Our Baby Be Defected?

Hi there,

I have taken this from the Centre for Genetics to explain, what it is I think you are asking!

GENES AND FAMILIES



The cells of the body contain information, in the form of genes, to tell the cells to make all the necessary structural components and chemicals for our health, growth and development. It is estimated that we all have approximately 30,000 pairs of genes in every cell of our body (for further information on genes, see Genetics Fact Sheet 1). If the information in a gene is changed, the correct message may no longer be sent to the cell, causing a problem with that cell's function. Changes that make the genetic information faulty are called mutations (Genetics Fact Sheet 2).



Genes come in pairs: one copy of each gene inherited from the mother and one copy from the father. Since there are two copies of the genes in the cells, a mutation in one of the gene copies that could be potentially harmful will generally have no direct effect on an individual's health. The correct gene copy will usually override the faulty copy of the gene. These mutations are called recessive (or hidden) to the correct copy and the individual is said to carry the faulty gene. Carrying a faulty gene usually causes no problem. But if an individual has two copies of the same faulty gene containing a recessive mutation, the cell will not receive any correct instructions to enable normal function and may result in the individual having a genetic condition (Genetics Fact Sheets 4 and 6).



Importantly, everyone carries several faulty genes without having any impact on their health or development.



There are thousands of possibly harmful faulty genes due to mutations but generally two unrelated people will not carry the same faulty genes. So children of unrelated parents are at low risk of inheriting from each of their parents a copy of the same faulty gene that could result in a genetic condition.

People who are blood relatives however, share a greater proportion of their genes than unrelated people. This is because they have a common ancestor such as a grandparent from whom they received their genes and therefore have a chance of carrying the same harmful, faulty recessive gene copies. The main concern is the possibility that a child will inherit two identical copies of a faulty gene containing a recessive mutation, resulting in a genetic condition.


RELATIONSHIPS BETWEEN BLOOD RELATIVES

Some relationships between blood relatives will be closer than others and they have therefore been classified by genetic specialists according to the degree of closeness, based on the proportion of their genes that they share:



Brothers and sisters, non-identical (dizygotic) twins, parents and children are first-degree relatives. They have half (1/2) of their genes in common.
Uncles and aunts, nephews and nieces, grandparents and half brothers and half sisters are second-degree relatives. They have a quarter (1/4) of their genes in common.
First cousins, half-uncles and aunts and half-nephews and nieces are third degree relatives. They have an eighth (1/ of their genes in common.

So if parents are close relatives, or there are a number of generations where the parents have been closely related, they are more likely to share the same faulty gene containing a recessive mutation than if they are unrelated.

WHAT IS THE RISK TO CHILDREN OF PARENTS WHO ARE CLOSE RELATIVES?


The risk that those marrying a relative are more likely to have offspring with birth defects or a disabling condition is nearly always exaggerated and perceived as being higher than it actually is.

All parents who are unrelated carry a risk of between 3 and 4% (3 to 4 out of every 100 births) of having a child with a birth defect or disability.

Where parents are first cousins and there is no family history of a specific condition, or where there is no other history of parents being related in previous generations, the risk is approximately double that for unrelated parents. So the total risk of having a child with a genetic condition where parents are first cousins is around 5-6%. Looked at another way, there is approximately a 95% chance of having an unaffected baby.

However, in societies with a tradition of first cousin marriage, and where marriages are usually contracted within the community, many couples are often more closely related than first cousins and consequently their risk may be significantly higher.

thanks for your reply.. so it means that our baby will be 50% with disablities?

Our mothes are blood related.. they are sisters. So we are 1st degree cousins.

does it means that we have only 50% chance for a normal baby?

Does any of your family have any condition that you know of?

"So the total risk of having a child with a genetic condition where parents are first cousins is around 5-6%. Looked at another way, there is approximately a 95% chance of having an unaffected baby"

You should be fine!

my mum passed away of a heart attack in her sleep.

But we're first degree cousins. Our mothers are sisters and of course we have different dads.