Prenatal Development

Haffner, W. J. J.(2007). Development before birth. In Batshaw, M. L., Pelligrino, L. & Roizen N. J. (Eds.). Children with disabilities (6th ed.). (pp. 23-34). Baltimore, MD: Paul H. Brookes Publishing Company.

Moore, K. L., & Persaud, T. V. N. (1993). The developing human: Clinically oriented embryology (5th ed.). Philadelphia, PA: W. B. Saunders Company.

Revised June 2008Development of Young Children with Disabilities

#872.514 (61)Carol Ann Heath

Pregnancy

Dating the pregnancy EGA- estimated gestational age (14

days longer than conceptional age, includes time between LMP and ovulation)

LMP- menstrual age is the time from the first day of the last menstrual period

Fertilization

If sexual intercourse occurs near the time of ovulation when the mature ovum (egg) is released, conception can occur.

Average duration of pregnancy is 280 days, or 40 weeks

EDD (estimated due date) = EDC (estimated date of confinement)

EDD- add 7 days to first day of LMP (last menstrual period) and subtract 3 months

Preterm delivery- prior to 38 complete weeks EGA (estimated gestational age)

Full term- between 38 and 42 weeks EGA

Post term birth- EGA greater than 42 weeks

Birth

A child is born Preceding months are complex and

numerous steps The egg is fertilized and implants In-utero development occurs

rapidly

When does the greatest risk for severe developmental disabilities occur?

The greatest risk for severe developmental disabilities occurs in the period between conception/implantation and birth(Decoufle et al., 2001)

Fewer than 10% of developmental disabilities occur during labor and delivery(Batshaw, 2002)

Fertilization

When the mature ovum (egg) is released and is penetrated by a sperm (the sperm can remain viable in the tubes for 2-3 days; the egg can only be fertilized for 12-24 hrs)

The Cell

Bodies are composed of over 100 trillion cells

Many types of cells Each cell divided into two

compartments: (1) central- the nucleus(2) outer area- the cytoplasm

The Nucleus

Houses chromosomes (Greek for “colorful bodies”)

Contain the genetic code- DNA DNA

(1) deoxyribonucleic acid(2) contains physical and biochemical properties

Chromosomes

Humans- 46 chromosomes 46 (diploid number) are divided

into 23 (haploid number) pairs of complementary chromosomes

In every chromosome pair, one comes from the mother/one comes from the father

Conception:

Egg & sperm cells each contain only 23 chromosomes

Sperm contributes 23 + X or 23 + Y Ovum contributes 23 + X Germs cells fuse to produce fertilized

egg = XX (female) XY (Y contributes “maleness”)

Embryonic Development: Day 1: Fertilization [2 weeks after LMP]

Sperm + Ovum = ZYGOTE

Day 2: Zygote divides; the group of multiplying cells is called the morula

Day 4 & 5: Blastocyst forms (develops hollow cavity) The blastocyst lies free in the uterine cavity for about 2 days before attaching, or implanting, to the endometrium (inside wall of the uterus)

This marks the formal beginning of pregnancy, nearly 5-7 days after ovulation & fertilization

What three types of cells does the embryonic stem differentiate into?

The embryonic stem cells differentiate into three types of cells: Ectoderm Mesoderm Endoderm

Embryonic development is divided into what two stages?

Embryonic- lasts from week 3 to week 8 after ovulation and fertilization, or week 5 to week 10 after the first day of the last menstrual period

Fetal- begins 8 weeks after ovulation and fertilization

Embryonic Development [Cont.]:

Day 6: Early implantation Day 7: Full attachment of embryo in

uterus In general, substances taken in wks 1

& 2 will either kill the embryo or enough cells recover to allow normal development

In general, no teratogenic effects

Embryonic Development [Cont.]:

Day 15: 1st missed period Day 16: 1st indications of neural

groove Week 3: Placenta formed; Week 4: Primitive; neural tube forms

Ear & eyes, lips, palate, jaw Upper limb buds

Embryonic Development [Cont.]:

Week 5: Heart tube forms Lower limb buds

Week 6: Oral + nasal cavities migrate If abnormal = Cleft lip/palate Tail present

Embryonic Development [Cont.]:

Week 7: Limbs bend Fingers/toes webbed

Week 8: Tail stub present

Embryonic Development [Cont.]:

Week 8: Fetus Head rounder Tail gone Cannot distinguish gender

Week 9: End of embryonic period CR = 3.25 inches

Start of fetal development

Fetal Development: Essential structures present 10th week:

Face appears child like Genitalia distinguishable Tremendous neurologic growth Organ maturation

Fetal Development [Cont.]:

5th & 6th mo- fingernails form, skin thickens, movements purposeful;

End of 6th mo- weighs 2 lbs, 14 inches long

Gestation = 38 weeks (since conception) Prematurity = < 35 weeks (3 weeks early) Postmaturity = > 40 weeks (2 weeks late)

Having a Baby

Approximately 266 days after conception, the process of labor begins.

The mothers immune system shuts down during the previous nine months but then decides to reject the baby.

Labor

First stage- Mild contractions with may be confused with Braxton-Hicks which occur throughout the pregnancy;

Within hours the contractions become stronger, longer and more frequent, allowing the babies head to get into position for delivery- the vertex position;

Labor- the presence of regular uterine

contractions leading to progressive effacement (thinning)

Dilation of the cervix Expulsion of the fetus

First Stage

Uterine contractions bring about effacement and progressive dilation of the cervix

Second stage

Baby’s head pushes through the birth canal and appears at the vaginal opening;

Cervix becomes fully dilated;

Third Stage

Usually lasts 10 to 15 minutes The complete expulsion of birth of

the newborn Nose and mouth are bulb-

suctioned to clear airway

Umbilical cord is wrapped around the neck in ¼ of births (nuchal cord)

Cord is clamped and cut

Other issues

Cesarean delivery- baby delivered through an incision in the abdomen and uterus; 5% in 1965 to 27.6% in 2003 (highest rate).

Dystocia- difficult labor Protraction disorders Cessation

In 9 out of 10 cases, the result is a ruddy-cheeked, screaming, healthy baby.