Congenital anomalies (birth defects) : Introduction, Symptoms, Causes, Diagnosis, Management and Prevention - www.genericdrugscan.com

Congenital anomalies (birth defects) : Information

Congenital anomalies (birth defects) can be defined as structural or functional anomalies (e.g. metabolic disorders) that occur during intrauterine life and can be identified prenatally, at birth or later in life. Congenital anomalies are also known as birth defects, congenital disorders or congenital malformations. Congenital anomalies are the major cause of new born deaths within four weeks of birth and can result in long-term disability with a significant impact on individuals, families, societies and health-care systems.

In nearly 50% of cases the exact cause of congenital anomaly could not be identified, although there are some known risk factors which can be linked with the causation of malformation. Congenital anomalies can be caused by single gene defects, chromosomal disorders, multifactorial inheritance, environmental teratogens (an agent, which can cause a birth defect) and micronutrient deficiencies.

According to the World Health Organization (WHO) in 2010, an estimated 270 000 deaths during the first 28 days of life were reported due to congenital anomalies globally.

According to March of Dimes (MOD) global report on birth defects 7.9 million births (6% of total births) occur annually worldwide with serious birth defects and 94% of these births occur in the middle and low income countries. According to joint WHO and MOD meeting report, birth defects account for 7% of all neonatal mortality and 3.3 million under five deaths.

The prevalence of birth defects in India is 6-7% which translates to around 1.7 million birth defects annually. The common birth defects include congenital heart disease (8-10 per 1000 live births), congenital deafness (5.6-10 per 1000 live births), and neural tube defects (4-11.4 per 1000 live births) (March of Dimes report, 2006).

Some birth defects are clinically apparent at birth; others may only be diagnosed later in life. The structural defect such as spina bifida is obvious at birth whereas haemophilia a functional defect (a bleeding disorder) is not usually obvious until infancy or childhood.

The Ministry of Health and Family Welfare, Government of India has addressed the problem with the implementation of various national health programmes. In 2013, National Child Health Screening and Early Intervention Services covered 30 health conditions of the children aged 0-18 years through various approaches.

India Newborn Action Plan (INAP) formulated in September 2014, has integrated the approaches for the prevention and care of newborn with birth defects into primary health care, with an emphasis on maternal and child health. INAP is Indias committed response to the Global Every Newborn Action Plan (ENAP) by WHO with a vision to eliminate preventable newborn deaths and stillbirths.

References-

www.who.int

www.ijpcbs.com

apps.searo.who.int

www.ncbi.nlm.nih.gov

nrhm.gov.in

Some birth defects are clinically apparent at birth; others may only be diagnosed later in life. The structural defect such as spina bifida is obvious at birth whereas haemophilia a functional defect (a bleeding disorder) is not usually obvious until infancy or childhood.

Approximately in 50 percent of birth defects a specific cause is not known. However, known causes can be divided broadly into two groups:

• Preconception causes are genetic and partially genetic, originating mostly before conception. Birth defects are due to abnormalities of the genetic material--chromosomes and genes including chromosomal abnormalities, single gene defects and multifactorial disorders (which are caused by the interaction of genes and the environment).
• Post-conception causes develop after conception, but before birth. Birth defect is caused by an intra-uterine environmental factor. This includes teratogens that interfere with normal growth and development of the embryo or foetus, mechanical forces that deform the foetus, and vascular accidents that disrupt the normal growth of organs.

Risk factors-

Socioeconomic and demographic factors:

• Congenital anomalies are more frequently seen among low income families and countries.
• About 94% of severe congenital anomalies occur in low- and middle-income countries due to poor access to sufficient and healthy food, increased exposure to various infections and alcohol (cause foetal alcohol syndrome) and insufficient health care delivery system.
• Maternal age: advanced maternal age increases the risk of chromosomal abnormalities, such as Down syndrome.

Consanguinity (when parents are related by blood) increases the prevalence of rare genetic congenital anomalies; it nearly doubles the risk for anomalies in first-cousin unions. Consanguinity rates in India vary from 1% to 4% in the northern region to 20-30% in the southern region (especially uncle niece marriage). Consanguineous marriage in Indian Muslim communities is 20-30%. Some ethnic communities (e.g. Ashkenazi Jews or Finns) have a comparatively high prevalence of rare genetic mutations, leading to a higher risk of congenital anomalies.

Infections: Some Maternal infections during pregnancy can increase the risk of birth defects such as:

• Rubella infection (German measles-a viral infection) to pregnant mother can result in to miscarriage, deafness, intellectual disability, heart defects and blindness in newborn.
• Toxoplasmosis (disease caused by parasite found in soil) infection during pregnancy can cause birth defects such as hearing loss, vision problems and intellectual disability.
• Sexually transmitted infections (STIs): such as syphilis, cytomegalovirus can cause serious birth defects.
• Zika virus infection: during pregnancy can cause certain birth defects (microcephaly and other abnormalities).

Maternal nutritional status and medical conditions:

• Iodine deficiency, folic acid deficiency, excessive Vitamin A intake may affect the normal development of an embryo or foetus, for example, folic acid insufficiency increases the risk of having a baby with a neural tube defect.
• Obesity, diabetes mellitus and seizure disorders may increase the risk of certain birth defects.

Maternal exposure to certain medications, psychoactive drugs, tobacco, radiation and pesticides during pregnancy may increase the risk of congenital anomalies in foetus or neonate. Working or living near, or in, waste sites, smelters or mines may also be a risk factor.

Certain drugs when taken during pregnancy may cause birth defects; these drugs are called teratogenic drugs (Category X drugs). Categories X drugs are contraindicated during pregnancy. (Drugs are categorized into 5 categories according to the development of adverse effects on the foetus, category A, B, C, D and X.)

Foetal age at drug exposure determines the foetal damage as:

• Before the 20th day after fertilization: there is all-or-nothing effect, either killing the embryo or not affecting it at all.
• During organogenesis (between 20 and 56 days after fertilization): teratogenic effects may occur at this stage.
• After organogenesis (in the 2nd and 3rd trimesters): teratogenic effects are unlikely, but drugs may alter growth and function of normally formed fetal organs and tissues.

Easy availability of drugs along with inadequate health services, intake of non-prescribed drugs and self-medication are some common problems.

www.who.int/

www.acog.org

www.msdmanuals.com

www.marchofdimes.org

apps.searo.who.int

For the detection of congenital anomalies screening can be done during preconception period, during pregnancy and after child birth.

Preconception screening: to identify those at risk of conceiving a child with a birth defect since inherited disorders tend to cluster within families.

• Using family history to identify individuals at risk of having affected children.
• Carrier screening for common recessive disorders (e.g. thalassaemia and sickle cell disorders).

Peri-conception screening: offering genetic counseling to women 35 years or older. Along with routine ultrasound other tests can be used for screening during the first trimester and the second trimester of pregnancy.

According to maternal characteristics/risk factors appropriate screening method can be used:

First trimester screening: is a combination of two tests performed between 11th and 13th weeks of pregnancy:

• Nuchhal translucency test: with the help of ultrasound thickness of the area at the back of the neck (foetus) is measured. An increase in the thickness can be a sign of Down syndrome.
• First trimester blood test: high levels of beta human chorionic gonadotropin (beta-hCG) hormone and low levels of pregnancy associated plasma protein A (PAPP-A) are related with certain birth defects.

When during first trimester screening nuchhal translucency test and maternal blood tests are used together, they have a greater ability to determine the chances of foetus might have a birth defect, such as Down syndrome (trisomy 21) and trisomy 18.

Second trimester screening: Second trimester screening tests are advised between 15th and 20th weeks of pregnancy.

• Triple screen test/ quad screening: The triple screen test is a maternal blood screening test that involves three specific substances: Alpha-fetoprotein test (AFP), human chorionic gonadotrophin (HCG), and estriol estimation. When a test for the hormone inhibin A is added, it's called a quad screening.
• Anomaly Ultrasound: The ultrasound is used to know about different parameters of foetus and looks for any birth defects.

The integrated test (first trimester screening tests plus the quad screening in the second trimester) correctly finds Down syndrome in about most of the cases. If the results of first trimester screening tests are abnormal, genetic counseling is recommended. Additional testing such as amniocentesis, chorionic villus sampling, cell-free fetal DNA or other ultrasounds may be needed for accurate diagnosis.

Amniocentesis: during pregnancy foetus is surrounded by amniotic fluid that can be used to detect genetic disorders in the foetus. It is not routinely advised to all pregnant women and is recommended in pregnancies with high risk factors for the congenital disorders, such as (pregnancies at advanced age) for Down syndrome, muscular dystrophy, sickle cell anaemia, thalassemia and cystic fibrosis.

Chorionic villus sampling (CVS): in this test cells from the chorionic villi (tissues from placenta) are examined for chromosomal disorders such as Down syndromes. CVS isn't routinely offered to all pregnant women. It's only advised for further diagnosis when antenatal screening tests/ routine ultrasound show abnormality.

Cell-free fetal DNA- It is a noninvasive prenatal screening that uses cell-free DNA from the plasma of pregnant women as a screening method for fetal aneuploidy. It can be used in women 35 years or older, ultrasonographic findings indicative of an increased risk of aneuploidy, women with a history of trisomy-affected offspring, and women with positive first-trimester or second-trimester screening test results.

Cordocentesis: also called percutaneous umbilical blood sampling, a small sample of the foetal blood is withdrawn from the umbilical cord for detection of foetal abnormalities after 17 weeks of pregnancy. It is an invasive diagnostic test. This test detects chromosome abnormalities and certain blood disorders.

Genetic services: There are 77 genetic counseling centers, 78 laboratories, and 37 prenatal diagnostic centers in India as listed on the national website*.

References-

www.nichd.nih.gov/

www.webmd.com

www.health.wa.gov.au

www.nhs.uk

www.nhs.uk/

www.ijpcbs.com/

www.acog.org/

* geneticsindia.org/

Management includes:

Neonatal screening including physical examination of all neonates and screening for functional disorders such as congenital hypothyroidism, phenylketonuria, sickle-cell disease and glucose-6-phosphate dehydrogenase deficiency by trained primary health care providers can be performed. Neonates with birth defects may be further referred to appropriate level of medical/surgical facilities.

Effective life-saving medical treatment is available for several birth defects with functional disorders such as thalassaemia (inherited recessive blood disorders), sickle cell disorders and congenital hypothyroidism (reduced function of the thyroid).

Many structural congenital anomalies (about 50%) can be corrected with paediatric surgery in early life, such as simple congenital heart defects, cleft lip and palate, club foot, congenital cataracts, and gastrointestinal and urogenital abnormalities. Simple, cost-effective, and non-invasive treatment also exists for certain conditions such as clubfoot.

Appropriate treatment is also needed for congenital disorders manifesting themselves after the neonatal period. This includes the early detection and treatment with rehabilitation services.

Ministry of Health and Family Welfare (MoHFW), Government of India has made a provision for prevention, early diagnosis and management of birth defects under India Newborn Action Plan (INAP), 2014 along with basic mother and child care*.

www.who.int/

*nrhm.gov.in

apps.who.int

Primary prevention is an important aspect in the prevention of congenital anomalies. It aims to ensure that individuals are born free of birth defects by being conceived normally and not being damaged in the foetal life. This can be achieved with basic reproductive health approaches which include family welfare services, promoting healthy dietary habits and lifestyle, safe food and environment; detecting, treating and preventing maternal infections; control of such diseases as insulin-dependent diabetes mellitus and epilepsy; vaccination, avoiding use of certain drugs during pregnancy and prior to conception (in women planning for the pregnancy).

• Family welfare services: enabling couples to space pregnancies and plan family size, define the ages at which they wish to complete their family and reduce the proportion of unintended pregnancies.
• Maintaining good preconception health of women: by improving their diet throughout their reproductive years with adequate amount of macronutrients and micronutrients (vitamins and minerals -iron, iodine and folic acid). Folic acid supplementation prevents neural tube defects. As the neural tube closes by 28th day after conception, when a woman might not know she is pregnant and most of pregnancies are not planned; all women who can become pregnant should take folic acid supplementation every day. Thus folic acid intake may be improved with daily oral supplements or fortification of staple foods such as wheat or maize flours.
• Promoting healthy lifestyle measures such as abstain from or restrict the intake of harmful substances (such as alcohol, smoking including passive smoking).
• Controlling pre-conceptional medical conditions/diseases such as insulin-dependent diabetes mellitus, epilepsy and STIs with proper drug treatment and counseling before and throughout pregnancy.
• Improving the coverage of rubella vaccination to all school-aged children and adolescents. The rubella vaccine can also be given (at least 1 month prior to pregnancy) to women who have not been vaccinated and do not have a history of rubella in childhood (two doses of rubella vaccine at an interval of four weeks).
• Avoiding environmental exposure to hazardous substances at home and workplace (e.g. heavy metals, pesticides) before and during pregnancy.
• Avoid harmful drugs and medical radiation during pregnancy and ensuring that any medications or medical radiation (e.g. imaging rays) given during pregnancy is safe and justified. As a rule, no medication should be taken during pregnancy without the advice of a doctor. Pregnant women should avoid intake of non-prescribed drugs and self-medication.
• Promoting various measures used to prevent mosquito bites and sexual transmission of zika virus to couples or women planning a pregnancy/during pregnancy; either living or travelling to areas where zika virus is in circulation*.
• The timely identification of a family risk of inherited disease, and carrier screening with genetic counselling, enable couples to limit family size where there is a known risk.
• Increasing and strengthening education of health staff and others involved in maternal and child health and promoting prevention of congenital anomalies.

Secondary prevention aims to reduce the number of children born with birth defects. With the use of medical genetic screening and prenatal diagnosis, birth defects are detected and the couple offered genetic counseling and therapeutic options.

Tertiary prevention is directed towards the early detection and management of problem once a child with a birth defect is born.

www.who.int

www.who.int

apps.who.int

www.marchofdimes.org

www.who.int/

* www.nhp.gov.in