Human development

Study Unit3

By C Settley

Learning Outcomes

• Demonstrate insight and understanding into the various environmental factors that influence the pre – natal period

• Discuss the effects of the following environmental factors on the prenatal period:

• Age of the parents• Nutrition of the mother• Radiation Rhesus factor• Diseases in the pregnant woman• The use of medication and drugs• The emotional state of the mother

The Germinal Period

• Begins with conception and lasts from one to two weeks

• Within approximately 24-36 hours after conception the zygote divides into 2 cells, these divide into 4 and so on

• While cell development takes place, the cell mass moves slowly through the fallopian tubes and reaches the uterus. In the uterus the cell mass attaches itself to the uterine mucous membrane (known as implantation)

The Embryonic Period

• Lasts from implantation until about 8 weeks after conception

• The developing organism is now known as an embryo

The Fetal Period

• Lasts from the end of the embryonic stage until birth

• Skeletal development occurs• And due to the movement of above, the

organism is now known as a fetus

Pre Natal Development

• Prenatal development is the process in which an embryo or fetus (or fetus) gestates during pregnancy. Normal prenatal development lasts about 38 weeks and is divided into three stages: germinal, embryonic, and fetal

Pre Natal Development

• The growth that happens during the nine months of prenatal development is nothing short of astonishing, but this period is also a time of great vulnerability.

• Fortunately, the effects of many of these hazards can be greatly lessened or even avoided entirely.

• While dangers do exist, the vast majority of babies are born healthy.

The effects of the age of the parents during the prenatal period:

• Two time periods are of special interest: adolescence and the thirties and beyond.

• Infants born to adolescents are often premature. • The mortality rate of infants born to adolescent

mothers is double that of infants born to mothers in their twenties.

• Down Syndrome, a form of mental retardation, is related to the mother's age

The effects of the age of the parents during the prenatal period:

• By age 40, the probability is slightly over 1 in 100.

• By age 50, it is almost 1 in 10.

• The risk is also higher before age 18.

• Women also have more difficulty in becoming pregnant after the age of 30

The effects of the nutrition of the motherduring the prenatal period:

• Women who begin pregnancy underweight, eat poorly during pregnancy, and consequently do not gain at least 1.5 kilograms per month in the second and third trimesters

• They run a much higher risk of having low birth weight babies.

• Research indicates that obese women should gain seven to 11 kilograms during pregnancy; normal-weight women 11 to 16 kilograms; and underweight women even more.

The effects of the nutrition of the motherduring the prenatal period:

• Beyond overall weight, certain nutrients defend against low birth weight, including zinc, iron, and folic acid.

• Indeed, malnutrition (not age) is the primary reason young teenagers tend to have small babies.

• They tend to eat unhealthily, and because their own bodies are still developing their diet is inadequate to support the growth of two.

The effects of Radiation Rhesus factorduring the prenatal period:

• Death of the fetus is the main radiation effect after exposures during the pre-implantation period

• With a genetic predisposition for certain developmental defects the rate of such defects can be increased by exposures to ionizing radiations

• Significant increases of malformations have been observed after certain radiation doses

The effects of Radiation Rhesus factorduring the prenatal period:

• Exposures during the zygote stage lead to dose effect relations without a threshold. It appears possible that such effects can also occur in humans when a genetic predisposition exists in individuals. These are rare cases

• Radiation exposures during the pre-implantation period can increase genomic instability (Genomics is a discipline in genetics that applies recombinant DNA, DNA sequencing methods, and bioinformatics to sequence, assemble, and analyze the function and structure of genomes (the complete set of DNA within a single cell of an organism)

The effects of diseases on the pregnant woman during the prenatal period:

• Many diseases are capable of injuring a growing fetus.

• For example, doctors discovered that when a mother contracts rubella (also known as the German measles) early in her pregnancy, her child might suffer blindness, heart abnormalities, and brain damage as a result. Since then, immunizations have dramatically decreased in incidence of rubella and lowered the number of children affected by the illness.

The effects of diseases on the pregnant woman during the prenatal period:

• Maternal diseases and infections can produce defects by crossing the placental barrier.

• Syphilis is more damaging later in prenatal development, four months or more after conception. Rather than affecting organ development as Rubella does, syphilis damages organs after they have formed. The importance of the mother's health to the health of her offspring is nowhere better exemplified than when the mother is infected with HIV

The effects of the usage of medication and drugs during the prenatal period:

• Harmful substances such as drugs or radiation that invade the womb and result in birth defects are called teratogens.

• Teratogens are especially damaging in the embryonic stage because it is a critical period in prenatal development. Later, during the fetal stage, the environment provided by the mother affects the baby’s size, behaviour, intelligence and health, rather than the formation of organs and limbs In the past, doctors believed that the placenta served as a barrier to protect the growing fetus against toxins

• Today, doctors recognize the effects of many medicinal drugs including anticonvulsants and most hormones

• Because of the potential dangers, it is important for pregnant women to avoid any medications that have not been specifically recommended by their doctor.

The effects of the usage of medication and drugs during the prenatal period:

• You've also probably noticed that most television ads for new medications include some type of statement warning that women who are pregnant or who may become pregnant should avoid taking the certain drugs.

• Because such medications are thought to be able to affect the fetus as early as 10 to 14 days after conception.

• Fortunately, because doctors and mothers-to-be are far more aware of the potential dangers, the rates of medication-linked birth defects have been reduced considerably over the past few decades.

The effects of the usage of medication and drugs during the prenatal period:

• Psychoactive Drugs• Unfortunately, prenatal damage caused by psychoactive

drugs such as alcohol, cocaine, heroin, inhalants, and tobacco are still far too common.

• All psychoactive drugs have a deleterious effect on prenatal development leading to problems including low birth-weight, premature birth, and impaired brain development.

• The effects of such drug use can lead to both short-term and long-term deficits.

The effects of the usage of medication and drugs during the prenatal period:

• Babies exposed to psychoactive drugs in-utero may show signs of drug withdrawal after birth, such as crying, startling, difficulty sleeping, and erratic eating.

• As they continue to develop and grow, these children may face learning problems such as an inability to pay attention, poor self-control, increased irritability, or even major developmental delays.

• Tobacco use can result in low birth-weight as well as an increased risk of abnormalities such as urinary tract and limb malformations.

The effects of the usage of medication and drugs during the prenatal period:

• Alcohol use during pregnancy causes fetal alcohol syndrome which is characterized by facial abnormalities including a smaller than average head size, a flattened nose, wide spacing between the eyes, and a narrow upper lip.

• Fetal alcohol syndrome also results in intellectual impairments, impaired physical growth, learning disabilities and behavioral problems.

The effects of the usage of medication and drugs during the prenatal period:

• Also prevalent are a higher incidence of preterm births and lower birth weights. Respiratory problems and sudden infant death syndrome are also more common among the offspring of mothers who smoked during pregnancy

• Tranquilizers taken during the first three months may cause cleft palate or other congenital malformations

Medication Potential Harm Effects

Alcohol FAS

Nicotine Miscarriage, premature/low weight births

Sedatives Problems with sucking and breathing

Opiates (pain killers) Convulsions, breathing problems, behavioural problems

Cocaine Prem. births, low birth weight, small skull

Aspirin Fetal bleeding, low birth weight

Anti- Epileptics Physical deformities, retarded growth

Anti- depressants Mental retardation, Physical deformities

Vitamin A Physical deformities

The effects of the emotional state of the mother during the prenatal period:

• The mother's stress can be transmitted to the fetus. • When a pregnant woman experiences intense fears,

anxieties, and other emotions, physiological changes occur in the fetus.

• These include changes in respiration and glandular secretions.

• For example, producing adrenaline in response to fear restricts blood flow to the uterine area and may deprive the fetus of adequate oxygen.

• Also, reassuring the mother of fetal well-being has positive outcomes for infants

References

 

•http://psychology.about.com/od/early-child-development/a/environmental-influences-on-prenatal-development.htm

Activities