Congenital Anomalies/Birth Defects

Congenital Anomalies/Birth Defects
Congenital Anomalies/Birth Defects

By: Mrs. Ida Sweetlin
Assistant Professor
College of Nursing
CMC, Vellore
Congenital anomalies (CA) / birth defects, are defined as structural, behavioural, functional and metabolic disorders that occur during intrauterine life during embryogenesis and can be identified prenatally, at birth or in infancy. Congenital anomalies or birth defects can occur in 2 - 4% of live births and in 20–30% of still births. The annual neonatal mortality worldwide due to congenital anomalies is estimated to be 3,03, 000. The leading causes of death among children under five in 2017 were preterm birth complications, acute respiratory infections, intrapartum-related complications, congenital anomalies and diarrhea. Congenital anomalies are also known as congenital disorders or congenital malformations and have a serious potential threat to the child's health, development and survival. Congenital abnormalities are considered to be the major cause of miscarriages, stillbirths, preterm births, and childhood morbidity. 

The prevalence of congenital anomalies varies in different geographical location indicating a complex interaction between genetics and environmental factors. It is pertinent to understand the etiology of CA inorder to prevent the occurrence. The causes of congenital anomalies include malformations in the embryo, disruptions in embryogenesis, deformations in the development and dysplasia (abnormal growth or development of a tissue or organ). The exact cause for the occurrence of congenital anomalies is not well defined although genetics (genetic mutations and chrosmosomal abberations) and environmental conditions such as exposure teratogens including harmful chemicals (pesticides), drugs (antiepileptics), radiation, maternal systemic illnesses (diabetes, hypothyroidism, pregnancy induced hypertension), maternal infections (AIDS, Rubella, CMV, Herpes) and alcohol and tobacco  usage and macro & micronutrient deficiencies (iodine & folic acid deficiency) play a major role in the occurrence of congenital anomalies. Structural and functional defects in the embryo are attributed to underlying genetic defects or chromosomal abnormalities. These defects may be due to one or both parents being genetic carriers, one or both parents sharing the disease state, or the occurrence of mutations. Also first trimester (gestational age 1–13 weeks) is generally considered the highest risk period with regard to exposure to teratogens and possible occurrence of birth defect in the fetus.
Congenital anomalies can be broadly classified as major and minor. Congenital anomalies can also occur as an isolated defect or as multiple defects. Most of the major congenital anomalies result in miscarriages, stillbirths and neonatal deaths. 

The major congenital anomalies include neural tube defects, congenital heart defects, orofacial clefts, gastrointestinal and genitourinary abnormalities. The pneumonic VACTERL denotes Vertebral anomalies, Anal atresia, Cardiac defects, Tracheoesophageal fistula, and/or Esophageal atresia, Renal and Radial anomalies, and Limb defects (VACTERL). Neural tube defects (NTDs) are among the common congenital anomalies that result in defects of the vertebrae, spinal cord, cranium, brain. The gastro intestinal anomalies include tracheoesophageal fistula; duodenal atresia; jejunal and ileal atresia; biliary atresia; choledochal cysts; intestinal duplications; Hirschsprung's Disease; congenital lung masses, gastroschisis; omphalocele; meconium ileus; imperforate anus.

The emotional and economic burden placed by the occurrence of congenital anomalies in families and communities is immense. The outcomes of congenital anomalies results in abortions, stillbirths, neonatal mortality and childhood mortality. With expanding technology and expert medical care the mortality of children born with congenital anomalies has decreased. The need for repetitive hospitalisations, repetitive surgeries and care of children with congenital anomalies places a huge emotional and financial burden to families. There is a strong need to prevent the occurrence of congenital anomalies. The prevention of congenital anomalies can be divided as primary prevention and secondary prevention.
Primary prevention programs are based on public education about reducing the preconceptional, prenatal risks and preconception counselling. Preconceptional risk factors includes consanguineous marriages (two blood relatives marrying each other), exposure to teratogens and micronutrient deficiencies. The objectives of preconception counselling include reducing congenital anomalies caused due advanced parental age such as Down syndrome, and autosomal dominant disorders, by reducing the occurrence of congenital abnormalities such as neural tube defects related to folate deficiency, and mental deficiency due to iodine deficiency, which can be achieved by promoting healthy nutrition for women of reproductive age and also by reducing the occurrence of hereditary disorders in high risk families through genetic counselling. Research suggests that supplementation with Folic Acid before the time of conception reduces the risk of NTDs to a great extent. Folic acid supplementation prevents the the occurrence of major congenital anomalies such as neural tube defects, congenital heart defects, obstructive urinary tract anomalies, limb deficiencies, orofacial clefts and congenital hypertrophic pyloric stenosis. Deficiency in folic acid intake in mothers is associated with preterm deliveries, intra-uterine growth retardation, placental abruption and infarction. On the other hand maternal folic acid supplementation helps in reduction of preterm deliveries and intra-uterine growth retardation.

Secondary prevention on the other hand includes prenatal screening and early identification and treatment of congenital anomalies. Early identification of congenital anomalies can be confirmed by ultrasonography, amniocentesis and chorionic villus sampling during the pregnancy. Amniocentesis is a procedure wherein by using a needle amniotic fluid is aspirated and tested for chromosomal abnormalities. Chorionic villus sampling is a procedure where  a small sample placental tissue is removed and tested for any chromosomal defects. In early pregnancy certain types of fetal malformations, like anencephaly, can be diagnosed at 10-14 weeks of pregnancy. Anomalies such as omphalocele and limb anomalies are also diagnosed using ultrasound in the first trimester, but other structural anomalies, like urinary tract abnormalities, are detectable later in pregnancy. Blood investigations such as maternal serum alpha-fetoprotein screen also indicate the presence of congenital anomalies such as downs syndrome. 

Ultrasound screening for fetal structural abnormalities is generally recommended at 19-21 weeks of gestational age for mothers. The use of modern technology in prenatal screening and diagnostic techniques have a high detection rate for fetal abnormalities. But it is also important to realise that not every anomaly can be detected by current screening practices. Mothers undergoing prenatal diagnosis must be fully informed about the risks and benefits of the procedures. The parents to be need to well informed of the possible outcomes such as having a child with special needs. On identification of any congenital anomaly early in pregnancy parents need to given the option of a medical termination of pregnancy owing to the risks of having a baby with a serious anomaly. If the parents wish to continue their pregnancy despite a congenital anomaly in the growing fetus other advanced treatment options such fetal surgeries (surgeries done before birth of the baby) for anatomic defects and the need for advanced treatment options during and after birth, surgeries and specific care needs to explained. If the couple is planning for a future pregnancy genetic counselling needs to be included. Genetic counselling is the process of providing knowledge about genetic diseases to individual and families at risk for a genetic disorder.

Congenital anomaly is a birth defect which has no specific cure. Medical and technological advancements help in early identification of a congenital anomaly in utero in the early stages of pregnancy and offer parents options. However primary prevention of congenital anomalies includes minimising risk such as exposure to teratogens such as drugs, alcohol, tobacco, and optimal nutrition for the mothers. Iodine supplementation provides protection against congenital hypothyroidism and folic acid supplementation offers protection against Neural tube defects, gastrointestinal anomalies and genito urinary anomalies. Therefore it is important that educate the families who are planning for a baby on the
importance of primary prevention techniques.

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