230 Prenatal

Prenatal Development

Adapted from OpenStax

Heredity

There are two types of gametes involved in reproduction: male gametes (sperm) and female gametes (ova)

Male gametes are produced in the testes through spermatogenesis beginning at about 12 years of age

Female gametes are stored in the ovaries and are present at birth though immature with only about 400 becoming mature eggs

(attribution: Copyright Rice University, OpenStax, under CC BY 4.0 license)

DNA

•DNA is a helix-shaped molecule made up of nucleotide base pairs [adenine (A), guanine (G), cytosine (C), and thymine (T)

•Each chromosome has sequences of DNA make up genes that control a number of visible characteristics

•Each gene has multiple variations or alleles (specific versions of genes)

•In meiosis, segments of the chromosomes from each parent form pairs and genetic segments are exchanged as determined by change

This image shows a full set of twenty-three pairs of chromosomes. Chromosomes one through twenty-two are the autosomes, and the chromosomes at the bottom right show the pairing for a biological female (XX) at conception. (credit: modification of work “Figure 7. Localization of Alu Sequences in Nuclei of Fibroblasts and Lymphocytes” by Andreas Blozer et al/PLOS Biology, CC BY 2.0)

What is DNA?

https://youtube.com/shorts/U-odM8nQ_a0?si=4R_MvRaHJISTVHN3

Genes

Each parent contributes half the genetic information carried by the offspring with the resulting characteristics determined by the interaction of parental genetic material

Genotype is the genetic makeup of the individual while the phenotype refers to the person’s inherited physical characteristics

22 of chromosomes from each parent are similar in length to a corresponding chromosome from the other parent with the remaining chromosome looks like an X or Y (XY: male; XX: female)

Multiple Choice

Half of your genes come from your mother and half from your father.

• True

• False

Genotype/Phenotype

Genotype is the genetic makeup of the individual while the phenotype refers to the person’s inherited physical characteristics

Dominant genes are expressed while recessive genes are only expressed in the absence of a dominant gene

Multiple Choice

What concept refers to observable physical traits?

• Phenotype

• Genotype

• Chromosomes

• Recessive Genes

Chromosomal Abnormalities

One of the most common chromosomal abnormalities is on pair #21, down syndrome

A chromosomal abnormality on #23 results in a sex-linked chromosomal abnormality

Turner syndrome occurs in 1 of 2,500 live female births when an ovum lacking a chromosome is fertilized by a sperm with an X chromosome, resulting in a zygote with an XO composition

Klinefelter syndrome (XXY)occurs in 1 out of 700 live male births and results when the ovum containing an extra X chromosome is fertilized by a Y sperm

(credit: modification of work “Down Syndrome Karyotype” by National Human Genome Research Institute/Wikimedia Commons, Public Domain)

Multiple Choice

Which is considered a sex-linked chromosomal abnormality?

• red hair

• Turner Syndrome

• Huntington Disease

• Down Syndrome

Prenatal Screening

Focuses on finding problems among a large population with affordable and noninvasive methods and commonly includes ultrasounds, blood tests, and blood pressure readings

Prenatal diagnosis focuses on pursuing additional detailed information once a particular problem has been found and can be invasive

Can detect problems such as neural tube defects, anatomical defects, anatomical defects, chromosomal abnormalities, and gene mutations

Prenatal diagnosis is intended to enable timely medical or surgical treatment of a condition, to give parents the change to abort a fetus, and to give parents the chance to better prepare for a baby with special needs

Why is Prenatal Testing Important?

https://youtube.com/shorts/GSWyq7IkWDw?si=Yxn4SWXwVq7sVU-6

Germinal Period

•The Germinal Period (Weeks 1-2)

•The fertilized egg forms a zygote as a one-cell structure

•The genetic makeup and sex of the baby are set

•During the first week, the zygote divides and multiplies through process of mitosis for about 7-10 days and has 150 cells then implants into the uterine lining

In the development of identical twins, a zygote splits into two separate but genetically identical zygotes. In the case of fraternal twins, two eggs are fertilized by two separate sperm at the same time. (credit: modification of work “Identical twins lg” by National Human Genome Research Institute/Wikimedia Commons, Public Domain)

The Embryonic Period

•The Embryonic Period (Weeks 3-8)

•Upon implantation, the multi-cellular is called an embryo

•The placenta, a structure connected to the uterus to provide nourishment and oxygen from the mother to the embryo via the umbilical cord, is formed

•Cells continue to differentiate, the heart starts beating, organs begin to form and function

•Growth occurs from head to tail(cephalocaudal) and from the midline outward (proximodistal)

•About 20% of organisms fail during the embryonic period

While pregnancy is often discussed in terms of trimesters, the developing fertilized egg goes through its own three transformative stages: the germinal, embryonic, and fetal stages. (attribution: Copyright Rice University, OpenStax, under CC BY 4.0 license; credit left: modification of work “Sperm-egg” by PD Images/Wikimedia Commons, Public Domain; credit middle: modification of work “Tubal Pregnancy with embryo” by Ed Uthman/Wikimedia Commons, Public Domain)

Your Baby's Growth

https://youtube.com/shorts/6hvRGjCNf6w?si=n0gHPjH65AnrSMYv

The Fetal Period

•The Fetal Period (Weeks 9-40)

•Fetus (at about 9 weeks), about the size of a kidney bean and begins to look human

•By 12 weeks, the fetus has all body parts

•By 16 weeks, the fetus is about 4.5 inches long with fully developed fingers and toes and visible fingerprints

•Organ systems continue to develop and rudimentary neurons in the brain are developed by 24 weeks

•The age of viability is reached at about 22 to 26 weeks

•By week 37 all of the fetus’s organ systems are developed enough that it could survive outside the mother’s uterus without risks associated with premature birth

3D Medical Animation - Child Birth Process

Stages of Birth

First Stage

￮Longest Stage

￮Uterus contracts

￮Cervix dilates

￮Discharge of blood or amniotic fluid

The stages of childbirth begin with stage 1, cervical dilation. (attribution: Copyright Rice University, OpenStax, under CC BY 4.0 license)

Stages of Birth

Second Stage

￮Baby through birth canal

￮10-40 minutes

￮Head normally delivered first

￮Mother pushes and relaxes

￮Episiotomy

Stage 2 of the labor process includes full dilation and expulsion of the newborn. (attribution: Copyright Rice University, OpenStax, under CC BY 4.0 license)

Stages of Birth

Third Stage

￮Placenta or afterbirth is delivered

￮Episiotomy sutured

￮Relatively painless

￮Or Cesarean Section

Stage 3 of labor involves the expulsion of the placenta. (attribution: Copyright Rice University, OpenStax, under CC BY 4.0 license; credit right: modification of work “Human placenta uterine side” by “Ravedave”/Wikimedia Commons, Public Domain)

Multiple Choice

Which stage of labor is typically the longest?

• the first stage

• the second stage

• the third stage

• they are all the same length

Why You Always Need Medical Supervision During Pregnancy

https://youtube.com/shorts/J5euE9nkz-c?si=5SZVYNNA5KFZKuCT

Complications

Top causes of pregnancy-related deaths include cardiovascular disease, non-cardiovascular diseases, and infection or sepsis

Spontaneous abortion, miscarriage, is experienced in approximately 20-40% of undiagnosed pregnancies and in 10% of diagnosed pregnancies and typically occurs before the 12th week of pregnancy

Teratogens

The developing child is most at risk for severe problems in the first three months

Teratogens are factors that can contribute to birth defects which include some maternal diseases, drugs, alcohol, and stress as well as environmental and occupational exposures

Alcohol: consumption particularly during the second month of prenatal development may lead to neurocognitive and behavioral difficulties that can last a lifetime and can frequently result in fetal alcohol spectrum disorders (FASD)

Tobacco: Nicotine levels travel through the placenta to the fetus and has been associated with low birth rate, placenta previa, birth defects, preterm delivery, fetal growth restriction, and sudden infant death syndrome

Medical interventions such as (a) ventilators and (b) incubators are tools used in neonatal intensive care units to help premature or high-risk newborns to recover and thrive. (credit a: modification of work “Lyra” by Chris Sternal-Johnson/Flickr, CC BY 2.0; credit b: modification of work “Incubator-tahrir” by United States Agency for International Development/Wikimedia Commons, Public Domain)

The Apgar Score

https://youtube.com/shorts/jrVWvxEUntA?si=IAiifI_4W7vc8pAY

APGAR

The condition of the newborn is often assessed at 1 minute and 5 minutes after delivery using the APGAR.

The APGAR scale is a measure of heart rate, respiration, muscle tone, reflex response, and color.

A skilled practitioner can conduct the APGAR easily and quickly.

The newborn is given a score of 0 to 2 on each of the measures. A perfect APGAR would be a score of 10. 

But few babies receive a 10 on their first reading. Less than five is a cause for concern. The score should improve upon the second reading.

Multiple Choice

What scale is used to assess newborns?

• Infant assessment scale

• Teratogen

• APGAR

• Ultrasound