Fetal development

Gestational age determined by

The last menstrual period

Last menstrual period

Time from the first day of the last menstruation

Postconceptual age/embryonic age

Time from the moment of conception; age of developing fetus

• 2 weeks less than gestational age

Full term

37-42 weeks gestational age

• Use 40 weeks for calculations

Chronological age

Days, weeks, or months since birth

Premature birth

Birth that takes place <37 weeks gestational age

Corrected/adjusted age

Subtract number of weeks premature from chronological age

Germinal

0-2 weeks

• Period of dividing zygotes, implantation, and bilaminar embryo

• Usually not susceptible to teratogen (all or nothing) typically results in prenatal death

Embryonic period

3-8 weeks

• Period of concern for major morphologic abnormalities if exposed to teratogen

• Development continues in cephalocaudal direction

• Hyperplasia and differentiation occurs

Hyperplasia

Increase number of cells

Differentiation

Cells become specialized

Fetal period

9 weeks - birth

• Period of physiologic defects and minor morphologic abnormalities

• Less susceptible to teratogens → but could cause fetal growth restrictions or placental distress

• Rapid proliferation & hyperplasia

• Organ and tissue differentiation continue

• Bones continue to ossify and remodel

• Appearance becomes more proportional

Teratogens

• Drug, environmental substance, or maternal condition that is cable of interfering with development of the fetus, typically results in birth defect

  • Medications

  • Maternal infections

  • Maternal disorders

  • Chemicals

  • Substances

Prevention of birth defects

• Not all can be prevented

• Early and regular prenatal appointments important

• 400 micrograms folic acid daily, starting at least a month before getting pregnant

• Do not smoke, drink alcohol or use recreational drugs

• Discuss medications w/ MD

• Prevent illness during pregnancy; flu shot, hand hygiene

Week 3 embryonic development

• Organization of embryonic disc into:

  • Endoderm

  • Mesoderm

  • Ectoderm

• Exposure to teratogens is most dangerous

Endoderm

Digestive tract

Mesoderm

Muscles, skeleton, circulation

Ectoderm

Skin and nervous system

Week 4 embryonic development

• Heartbeat present

• Neural tube closure

• Limb buds form

Week 6 embryonic development

• Placental circulation functional through umbilical cord

• Brain division and cerebral hemispheres

• CV system functioning

• Eyes w/ eyelids

• Vertebrae begins to form

Week 8 embryonic development

• Eyes, ears, nose, mouth, fingers, toes, heart formed

• Embryo looks like a human and all tissues formed

If neural tube is disrupted…

Possible outcomes:

• Anencephaly

• Craniorachischisis

• Open spina bifida

• Closed spina bifida

• Encephalocele

• Iniencephaly

Weeks 9-16 fetal development

• Cartilaginous skeleton formed

• Swallowing emerges

• External genitalia visible by 12 weeks

• Eyes move

• Developmental reflexes strengthen

Weeks 17-20 fetal development

• Mother can feel fetal movement towards end stages

• Skin covered in lanugo: layer of fine hair

• Adipose tissue

• Lung maturation continues

• Diagnosis of congenital heart defects

• Not able to survive if born before 21 weeks

Weeks 21-29 fetal development

• Fetus viable at 23 weeks if born prematurely

• Accelerated weight gain

• Ongoing lung development, begin to produce surfactant (24w)

• Eyes fully developed by week 25

• By week 29:

  • All external characteristics of full-term infant present

  • Hair, nails

  • All neonatal reflexes present

  • Able to cry audibly

Weeks 30-38 fetal development

• Weight gain continues → fat accumulation for insulation over last weeks

• Thermal regulation established by week 32

• Fetal movements decrease → d/t decrease space or maturation/stability

Normal birth

• Head down (vertex), face down

• Head should be slightly smaller than pelvic outlet

• Entry into world can be traumatic

• Should breathe on their own within fa few seconds

• Shift from fetal circulation to adult

Breech birth

• Places fetus at higher risk for oxygen deprivation, brith trauma to mother and fetus and higher risk for NICU stay

• Multiple diff positions other than normal

APGAR

A - appearance

P - pulse

G - grimace

A - activity

R - respiration

Appearance

0 - pale or blue

1 - extremities blue, trunk/head pink

2 - pink

Pulse

0 - no pulse

1 - less than 100 bpm

2 - greater than 100 bpm

Grimace

0 - no response to stimulation

1 - weak cry

2 - cries and pulls away

Activity

0 - no movement

1 - arms, legs flexed

2 - active movement

Respiration

0 - no breathing

1 - slow, irregular

2 - strong cry

APGAR min 1

7-10: routine care

4-6: some assistance for breathing may be required

<4: lifesaving measures

APGAR min 5

7-10: normal

<7: ongoing monitoring every 5 min, up to 20

Normal birth weight

> 5 pounds, 8 ounces (2500g)

< 8 pounds, 14 ounces (4000g)

Small for gestation age

< 5 pounds, 8 ounces or 2500 grams

Low birth weight

1500 g to < 2500 g

Very low birth weight

1000 to <1500 g

Extremely low birth weight

<1000 g

Fetal alcohol syndrome

• Caused by prenatal exposure to alcohol

  • Enters baby’s bloodstream through placenta

• Prevalence is 1%

• #1 cause of intellectual disability in the world

Neuromuscular impairments related to FAS

• Fine and visual motor deficits

• Impaired balance, coordination, and motor development

Musculoskeletal impairments related to FAS

• Facial; smooth philtrum, thin upper lip, broad nose

• Poor growth, microcephaly

• Abnormal joint position or function

• Short stature

Cardiopulmonary impairments related to FAS

• Heart defects

Behavioral/cognitive impairments related to FAS

• Hyperactivity

• Poor memory and attention (intellectual disability)

FAS in infants

• Low birth weight

• irritability

• Sensory sensitivity to light

• Poor sucking

• Global developmental delay

• Poor sleep wake cycles

• Increased ear infection

FAS in toddlers

• Poor memory capacity

• Hyperactivity

• Impulsive/lack of fear

• Lack sense of boundaries (need for excessive physical contact)

FAS in school-age

• Short attention span

• Poor coordination

• Difficulty w/ both fine and gross motor skills

• Learning disabilities

FAS in adolescents

• Trouble keeping up in school

• Low self-esteem from recognizing that they are different from their peers

• Poor impulse control

FAS in adults

• Poor life skills

• Ie. daily obstacles, affordable and appropriate housing, transportation, employment and money handling

Neonatal abstinence syndrome

• An array of behaviors seen in the newborn following abrupt termination of gestational exposure to substances

  • Opioids

  • Alcohol

  • Antidepressants

  • Antipsychotics

  • Heroin

  • Methadone

Presentation of neonatal abstinence syndrome

• Low birth weight

• High pitched cry, irritable

• Impaired state regulation

• Hyperactive reflexes

• Transient tone

• Feeding difficulties

• ANS dysfunction

Treatment for NAS

• Gradual wean off substance

  • Replace w/ morphine, methadone

• PT, OT, SLP to help with state regulation, positioning, feeding

Microcephaly

Small head and brain, often with intellectual disability

Anencephaly

Absence of the cranial vault, failure of rostral neural tube to close resulting in an absence of the cerebral hemispheres, condition is incompatible with life

Encephalocele

Sac-like protrusion or projection of the brain and the membranes that cover it through an opening in the skull

Omphalocele

Herniation of the intra-abdominal contents into the base of the umbilical cord — requires progressive compression of the abdominal contents and skin closure

NAS across the lifespan

• Signs of withdrawal will decrease over the length of stay in NICU

• Potential persisting impairments:

  • Vision problems

  • Motor impairments

  • Behavioral/cognitive problems

  • Sleep disturbances