Birth effects -its causes

 

Keep remembering the Types of birth defects for easy counseling of subsequent pregncaies : :

There are two main kinds of birth defects: A) structural and B) functional/developmental. The second group mainly is due to genetic or chromosomal disorders.

What are the etiologies of BD(birth defects) ? Unfortunately  we have no answer to couple to explain  the causes in  about 70 percent of birth defects The cause reamaing unknown but only thing most of  cases we  can diagnose structural defects by 19 weeks scan but structural defect do appear later when our tied and we are helpless as we can’t do termination. .

I.    Structural birth defects are related to a problem with body parts. Some examples are cleft lip or cleft palate, heart defects, such as missing or misshaped valves and abnormal limbs, such as a club foot. They also include neural tube defects, such as spina-bifida. Most importantly we can pick up problems that are related to the growth and development of the brain and spinal cord (Ventriculomegaly, hydrocephaly, agenesis of C callosum) ..

II.       Functional birth defects are related to a problem with how a body part or body system works. These problems often lead to developmental disabilities and mostly realted to genetic defects. The common examples are  :

A)               Nervous system or brain problems – such as learning disabilities, intellectual and developmental disabilities, behavioral disorders, speech or language difficulties, convulsions and movement trouble. e.g. : Autism, Down syndrome, Prader-Willi syndrome and Fragile X syndrome.

B)                Genetic birth defects have three main categories:

·    B-1) Single-gene defects.  B-2  Chromosomal birth defects .B-3 .Multifactorial birth defects

What are genetic & multifactorial birth defects ? Type B 1: Single-gene defects: A mutation (change) in a single gene can cause birth defects. e.g. dominant inheritance. Each child of a parent with the gene has a 50-percent chance of inheriting the disorder. e.g. : Achondroplasia ,,Marfan syndrome.

Other genetic diseases are inherited when both parents (who do not have the disease) carry an abnormality in the same gene and pass it on to a child. This is called recessive inheritance. Each child of two parents who have the abnormal gene has a 25-percent chance of inheriting the disorder. e.g : Tay-Sachs disease, Cystic fibrosis. X-linked: e.g. : Hemophilia, Duchenne muscular dystrophy.

Type B 2 defects : Chromosomal birth defects : Abnormalities in the number or structure of chromosomes can cause many birth defects. e.g. : Down’s syndrome (Trisomy 21 or other rearrangements resulting in extra genetic material from this chromosome).Trisomy 18 and 13. Affected babies have multiple birth defects and often in the first months of life. Sex chromosome abnormalities (missing or extra copies of the sex chromosomes, X and Y). e.g. : Turner syndrome, Klinefelter syndrome.

Type B-3   defects : Multifactorial birth defects may be due to a combination of genes and environmental exposures. This is called multifactorial inheritance. In some cases, an individual may inherit one or more genes that make him more likely to have a birth defect if she is exposed to certain environmental substances, such as cigarette smoke. But if there is no exposure to the environmental substance before birth, she probably won’t have the birth defect. E.g. Cleft lip / palate, Neural tube defects (NTDs) spina-bifida and anencephaly and Heart defect.  Environmental substances that can cause birth defects are called teratogens. These include alcohol, certain drugs/medications, infections and certain chemicals.

 

Alcohol : Each year between 1,000 and 6,000 babies in the Untied States are born with fetal alcohol syndrome (FAS) . This is pattern of mental and physical birth defects that is common in babies of mothers who drink heavily during pregnancy. Even moderate or light drinking during pregnancy may harm the baby.

Drugs : Illegal drugs, including cocaine, marijuana and Ecstasy, may cause birth defects and must be stopped if a women contemplates a pregnancy, medical help may be required to help her.

Infections : Certain infections can cause birth defects when a woman gets them during pregnancy. About 30,000 babies a year (about 1 in 150 newborns) in the US are born with a viral infection called cytomegalovirus (CMV) . About 8,000 infected babies each year develop permanent disabilities, including mental retardation and loss of vision and hearing. Pregnant women often get CMV from young children who have few or no symptoms. Take home message: Pregnant women may avoid as far as possible to come in contact with young children who may harbour CMV infection (asymtomatic carriers).

Sexually transmitted infections (STIs) : Untreated syphilis can cause stillbirth, newborn death or bone defects .