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PRENATAL PERIOD

Mae Linda G. R. de Luzuriaga, MD, FPPA

College of Medicine, USLS

 

 

General Objective:

To understand human prenatal development

 

Specific Objectives:

-       To discuss the relevance of understanding prenatal events and its effects on successive development of the human being

-       To understand the biological activities occurring in utero

-       To discuss prenatal development of the nervous system

-       To describe the prenatal influences on fetal development

-       To know the different maternal stresses, which could be transmitted to the fetus

-       To know the prenatal disorders affecting fetal development

 

The pregnant woman undergoes marked biological, physiological and psychological changes.

 

Attitudes toward pregnancy reflect deeply felt beliefs about reproduction, the timing, quality of marital relationship, whether she is married, age, history, sense of identity and reactions to motherhood.

 

In the psychologically healthy woman, pregnancy is an expression of her sense of self-realization and identity as a woman.

 

Negative attitudes about pregnancy are associated with the fear of childbirth or mothering role.

 

Some women view pregnancy as a way of diminishing self-doubts about their femininity or as means of reassuring themselves that they could conceive.

 

During the pregnancy esp. the first, the mother recapitulates early stages of her own development.

Psychological attachment to the fetus begins in utero.

 

The fetus is perceived as a separate being even before birth and is endowed with a prenatal personality.

 

In general, the psychodynamics of pregnancy is based on the developmental history of the person.

 

After implantation, the egg begins to divide, this is known as the embryo

 

Growth & development are rapid so that by the 8th week, the shape is recognizably human; at this stage this is known as the fetus

 

The fetus maintains an internal equilibrium that interacts with the intrauterine environment with variable effects.

 

The average newborn weighs 7.5 lbs.

 

By the 26th-28th week of gestation the premature born fetus has a good chance of survival.

With each increment of 100 g there is a progressively better chance of survival.

 

Prenatal events have great relevance to Psychiatry because the development of the embryo & fetus could be problematic for a variety of causes & can affect future behavior in many ways.  For example, the person’s genes exert their effects throughout life.

 

By birth the person may have a predisposition at the genetic level to the development of an abnormal state that can appear at anytime during the life span.

 

A predisposition to anxiety maybe present because of a cerebral disorganization in utero that manifests itself in perceptual motor dysfunctions and impulse control problems later in life.

 

Genetic factors may have delayed effects e.g. Huntington’s disease. This manifest in middle adulthood and life events play no part in the development of the disease.

 

Damage at the fetal stage is usually more global than is damage after birth.

 

Rapidly growing organs are the most vulnerable.

 

FETAL LIFE

 

A great deal of biological activity occurs in utero.

 

A fetus has a variety of behaviors that are necessary for adaptation outside the world.

 

Mothers are able to feel the motoric behavior of the fetus.

 

Fetal movements are usually detected at 16-20 weeks of gestation.

 

By the 14th week it can be artificially set into total body motion in utero by stimulation of its ventral skin surfaces.

 

On the 18th week it is able to hear & to respond to loud noises.

 

Smell & taste develop by about the 18th week as well.

 

The fetus responds to substances that maybe injected into the amniotic sac such as contrast medium.

 

Reflexes present in utero and at birth:

1.       Grasp reflex – 17 weeks

2.       Moro (startle) – 25 weeks

3.       Sucking – 28 weeks

 

Other reflexes:

Rooting, Babinski, Knee jerk, abdominal, tonic neck, grasp, startle

Tonic neck reflexes disappear by the 4th month after birth

 

DEVELOPMENT OF THE NERVOUS SYSTEM

 

The nervous system arises from the neural plate which is a dorsal ectodermal thickening that appears at about the 16th day of gestation.

 

By the 16 week part of the neural tube becomes the cerebral hemispheres.

 

Spina bifida & anencephaly are 2 forms of neural defects with incidence of 0.5/1000 births.

The cerebral cortex develops by the 10th week but layers do not appear until the 6th month of pregnancy.

 

The sensory & motor cortex are formed before the association cortex.

 

Brain function in utero is detected by fetal encephalographic responses to sound.

 

At birth human brain weighs 350 grams & reaches 1450 g at full adult development.

 

During fetal life & early infancy the number & the branching of dendrites & synaptic junctions grow enormously.

 

 

ANTEPARTUM MATERNAL HEALTH AND FETAL DEVELOPMENT

 

The fetal nervous system is highly susceptible to damage from a variety of causes.

 

The following are some causes:

Infections, malnutrition, hormonal excess or deficiency, drugs, alcohol smoking, radiation, medications.

 

TRANSMISSION OF MATERNAL STRESS

 

The fetus is responsive to emotions in the mother.

 

Maternal stress may influence the newborn through the placental transfer of adrenal hormones such as epinephrine and cortisol.