Prenatal Development



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Sandra G Smith Lifespan Development Ivy Tech Community College October 7, 2011 1 Envision a journey of being pregnant and you are eagerly awaiting the child that you have longed for. The arrival is drawing near and you never prepared or anticipated your child being born with a defect or later displaying displaced behavioral problems. Only to find out, that the teratogens you had been exposed to or exposed your unborn child to during pregnancy, could be the cause of this abnormality. Would one remain in a constant state of fear with every food, drink, or medication they ingested? Would one remain indoors in a glass bubble?

Unfortunately, one cannot hide from all of life’s environmental factors, but one can educate them self enough to know what studies have proven to be harmful teratogens to their unborn child, especially during the embryonic period. “A teratogen is any agent that can potentially cause a birth defect or negatively alter cognitive and behavioral outcomes. The field of study that investigates the causes of birth defects is called teratology. Some exposures to teratogens do not cause a physical defect but can alter the brain that is developing and influence cognitive and behavioral functioning, which is call behavioral teratology.

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The danger of structural defects caused by teratogens normally occurs earlier in the embryonic development rather than the fetal development, due to the fact it is the critical period for development of the nervous system (Santrock, Thirteenth Edition). The embryonic period is the period of prenatal development that occurs from two to eight weeks after conception. The rate of cell differentiation strengthens, support systems for cells cultivate, and organs appear. Damage during the germinal period often will prevent implantation.

In the beginning of the embryonic period, blastocyst attach to the uterine wall. The mass then becomes the embryo and three layers of cells form; the embryo’s endoderm (inner layer) which will form the digestive and respiratory system, the mesoderm (middle layer) which will become the circulatory system, and the ectoderm (outermost layer) which will form the brain and the nervous system, sensory receptors, and skin parts (Santrock, Thirteenth Edition). By the time most women know they are pregnant, the major organs have began to form.

While the organs are beginning to form they are most vulnerable to environmental changes. Into the third week the neural tube that eventually becomes the spinal cord has begun forming, eyes begin to form at approximately 21 days, the urogenital system becomes evident, arms and legs surface, four chambers of the heart begin to take shape, and blood vessels appear. Starting at the fifth into the eighth week; arms and legs become more distinguished, the face starts to form but is still not very recognizable, the intestinal tract develops and the facial structures fuse (Santrock, Thirteenth Edition).

Birth defects are structural malformations present not only occur in the fetus but can occur after birth, having an impact on multiple organs. These defects can transpire for several reasons, including, but not limited to, exposure to teratogens, genetic factors, injury at birth, and in most cases the reasons are unknown. In the USA, one of every 33 babies will or have been born with a birth defect such as congenital heart defect, neural tube defect, cleft lip, spina bifida, 2 and anencephaly.

All women are at risk of having a baby with a congenital defect, regardless of age, race, income or place of residence (Zhu, Kartiko, & Finell, 2009). One of the most amazing phases of the prenatal period is the development of the brain. As the human embryo develops in the mother’s womb, the nervous system begins to form as a long hollow tube located on the embryo’s back. Approximately at the 23rd prenatal week, connections between neurons begin to occur and there is almost a linear relationship between IQ measured later in life and the gestation at which the baby is born.

At the time of birth, babies have developed close to 100 billion neurons that handle information processing, at the cellular level in the brain. Two birth defects associated to a failure of the neural tube to close are anencephaly and spina bifida (Santrock, Thirteenth Edition). Neural tube defects (NTD’s) are a common type of birth defect occurring in nearly every 1-2 per 100 births. They take place when the neural tube fails to close throughout fetal development, leading to spina bifida (incomplete spinal column formation) or anencephaly (incomplete brain and skull formation).

Both of these can occur due to genetic or environmental factors. Occupational exposure to hazardous air pollutants such as benzene, have been linked in some studies to NTD’s. Maternal folic acid deficiency has also been strongly associated with NTD’s during the periconception period (time preceding, including and immediately following human conception). While most prenatal vitamins contain the recommended daily allowance of folic acid, this may not be unattainable in some women due to a common genetic mutation. This mutation results in a defect in folic acid metabolism (Barrett, 2011).

Spina bifida is the outcome from the failure of fusion of the caudal neural tube, and is considered one of the most common malformations in the human structure. At birth, girls are more prominently affected by this than boys. Although most causes are unknown this disorder can be due to occurrences such as chromosomal abnormalities, single gene disorders, and teratogenic exposures. Up to 70% of spina bifida cases could be prevented by the mother taking folate and folic acid supplementations, before and during early pregnancy.

Surgical closure of the spine is primarily done in the neonatal period and medical management is necessary throughout the lifetime. A family history of spina bifida or anencephaly is one of the strongest risk factors for this disorder, which can range from siblings to second and third degree relatives of infected relatives. Women with pregastational diabetes are at increased risk of delivering a child with spina bifida and other types of birth defects, which could be due to the degree of maternal metabolic control and first-trimester blood glucose concentrations.

Many anticonvulsant drugs (e. g. , epilepsy, bipolar disease, migraine headaches, chronic pain) are known teratogens (Mitchell, Atzick, Melchionne, Pasquariello, Sutton & Whitehead, 2004). Congenital heart disease (CHD) is the existence of a structural heart defect at birth. Often, this defect is undetected due to the size of fetal structures compared to the degree of resolution of the ultrasound equipment, creating strain on the parents to make irreversible 3 decisions in choosing the appropriate medical procedure (Smith, Newey, Jones, & Martin, 2011).

CHD is the leading congenital malformation with an incidence of 1% among live births, still being a major cause of morbidity and mortality in childhood (Nikkila, Bjorkhem, & Kallen, 2007). Since antidepressants have been found to increase the risk of heart disease to the fetus, failing to control various maternal factors that can influence birthing outcomes, such as maternal illness or problematic health behaviors, can make medical necessity determination difficult (Santrock, Thirteenth Edition). Craniofacial abnormalities consist of a significant amount of morbid human birth defects. /700 newborns are inflicted with a cleft lip which can require a great deal of medical treatments including surgical procedures, nutritional diets, extensive dental work, speech therapy, medical and behavioral interventions, creating a significant financial burden to the families. It has been found that mothers that consume large amounts of vitamin A, whom smoke or drink alcohol during pregnancy (alcohol induces the alcohol fetal syndrome) can sustain a greater chance for the unborn child to develop a cleft lip.

It is clear that avoiding these common environmental factors can greatly reduce your chance of your unborn child developing a cleft lip. (Murray, 2002). There are several self induced teratogens that maternal mothers knowingly subject their unborn fetus to knowing the consequences can be grave. Such as the impact of maternal smoking during pregnancy which impairs placental development, by reducing blood flow directly or indirectly, which can lead to a reduced flow of oxygen and micronutrients to the fetus.

Smoking censation during the early stages of prenatal have proven to lessen the risk as well as reduce low birth weight (Vardavas, Chatzi,Patelarou, Plana, Sarri, Kafatos & Kogenivas, 2010). Not only can maternal smoking cause low birth weights but can also be the cause of respiratory problems, sudden infant death syndrome, and cardiovascular problems. It has also been known to be a risk factor of attention deficit hyperactivity disorder (Santrock, Thirteenth Edition).

Attention deficit disorder (ADHD) can have a serious impact on ones social, academic, and psychological well being if not treated, both for the enduring and the parents. The medication alone can have an impact on appetite, sleeping causing insomnia, headaches, abdominal pain, and irritable mood (Withrow, Hash & Holten, 2011). Studies have found that not only alcohol, tobacco, and low birth weight can be factor of ADHD but also the season conception took place. This could be factored that the mothers suffered allergies during this period, causing respiratory infections, early in the first weeks of pregnancy.

ADHD has also been found to be caused by medication exposure. Studies show that children who take Phenobarbital for febrile seizures or epilepsy can develop hyperactivity symptoms (Pineda, Palacio, Puerta, Merchan, Arango, Galvas, & Arcos – Burgos, 2007). Alcohol consumption can be devastating to the fetus. Fetal alcohol spectrum disorders (FASD) are a cluster of abnormalities and problems that appear in the offspring of mothers who drink heavily while pregnant. These abnormalities can include deformities, defective limbs, face, 4 and head.

Most children experience a below average intelligence and have learning difficulties with some that are mentally impaired. It is generally agreed that a small amount of alcohol is okay for the maternal mother to consume but overall it still can affect the fetus (Santrock, Thirteenth Edition). Some children are never diagnosed correctly with FASD, possibly due to the fact they were adopted or fostered out, leaving the new parents unaware of what is causing the “difficult” ,behavior, therefore leaving their behavior misunderstood (October & Zolotova, 2011).

Cocaine, marijuana, and methamphetamine all have the possibility of leading to a lower intelligence in children. Methamphetamine and cocaine are stimulants which speed up the nervous system. This can cause a number of problems such as high infant mortality rates, low birth weight, and developmental and behavioral problems (Santrock, Thirteenth Edition). Babies of maternal mothers who use heroin have several difficulties at birth such as withdrawal symptoms, tremors, irritability, abnormal crying, and disturbed sleep and impaired motor control.

Many of the infants will show behavioral problems by their first birthday which often leads into attention deficit later in life (Santrock, Thirteenth Edition). It is obvious that one cannot create an environment where they can hide from all of life’s environmental factors. No matter what precautions one can take no one can alter the seasonal changes, environmental chemicals one is exposed to daily and medical necessity treatments, when pregnant. However, one can take precautions and explore avenues that can eliminate some of the toxic effects to the fetus during the embryonic period.

Certainly, one can avoid self inflicted teratogens such as tobacco, alcohol, cocaine, heroin, and excessive intake of caffeine. The embryonic period is such an amazing and crucial period of the prenatal development. Life is truly a miracle! References Amarin, Z. O. , & Obeidat, A. Z. (2010). Effect of folic acid fortification on the incidence of neural tube defects. Paediatric & Perinatal Epidemiology, 24(4), 349-351. doi:10. 1111/j. 1365-3016. 2010. 01123. x Barrett, J. R. (2011). Not Just for Workers: Maternal Exposure to Ambient Benzene Linked to Spina Bifida in Infants.

Environmental Health Perspectives, 119(3), A133. Retrieved from EBSCOhost Mitchell, L. , Adzick, N. , Melchionne, J. , Pasquariello, P. , Sutton, L. , & Whitehead, A. (2004). Spina bifida. Lancet, 364(9448), 1885-1895. Retrieved from EBSCOhost. Murray, J. (2002). Gene/environment causes of cleft lip and/or palate. Clinical Genetics, 61(4), 248-256. doi:10. 1034/j. 1399-0004. 2002. 610402. x Nikkila, A. , Bjorkhem, G. , & Kallen, B. (2007). Prenatal diagnosis of congenital heart defects–a population based study. Acta Paediatrica, 96(1), 49-52. doi:10. 1111/j. 651-2227. 2006. 00023. x October, A. , & Zolotova, E. (2011). Fetal alcohol syndrome: dashed hopes, damaged lives. Bulletin of the World Health Organization, 89(6), 398-399. doi:10. 2471/BLT. 11. 020611 Santrock, J. A. (Thirteenth Edition) Life-Span Development Smith, M. , Newey, C. , Jones, M. , & Martin, J. (2011). Congenital heart disease and its effects on children and their families. Paediatric Nursing, 23(2), 30-35. Retrieved from EBSCOhost. Vardavas, C. I. , Chatzi, L. , Patelarou, E. , Plana, E. , Sarri, K. , Kafatos, A. , & … Kogevinas, M. (2010).

Smoking and smoking cessation during early pregnancy and its effect on adverse pregnancy outcomes and fetal growth. European Journal of Pediatrics, 169(6), 741-748. doi:10. 1007/s00431-009-1107-9 Withrow, L. M. , Hash, P. K. , & Holten, K. B. (2011). Managing ADHD in children: Are you doing enough?. Journal of Family Practice, 60(4), E1-E3. Retrieved from EBSCOhost. Zhu, H. H. , Kartiko, S. S. , & Finnell, R. H. (2009). Importance of gene–environment interactions in the etiology of selected birth defects. Clinical Genetics, 75(5), 409-423. doi:10. 1111/j. 1399-0004. 2009. 01174. x

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