2010 BGD Practical 12 - Neonatal

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Practical 12: Embryo to Fetus | Second Trimester | Third Trimester | Birth | Neonatal | Abnormalities


Introduction

Newborn.jpg

The neonatal period (birth to 1 month) is a time of extensive and ongoing system transition from uterine environment to external world, this includes the initial period after birth which is referred to as the perinatal period.

It would seem obvious to say that development does not stop at birth. In fact many systems (cardiovascular, respiratory, gastrointestinal, homeostasis) undergo significant changes at birth, and many others (neural) have not yet completed their development. Note this current project focuses on prenatal development, so postnatal content is not as detailed.

Newborn Homoeostasis

Brown adipose tissue

Newborn has to establish new functioning systems in a balanced and regulated manner (homoeostasis).

  • lung function
  • circulatory changes
  • thermoregulation
  • endocrine function
  • nutrition
  • gastrointestinal tract function
  • waste
  • kidney function

Glucocorticoids - have an important role in the preparation for birth, including involvement in lung and cardiac development, and the maturation of enzymes in a variety of pathways.

Puerperium - The six weeks following parturition (birth) when maternal reproductive organs and physiology return to pre-pregnant state.


Respiration

Neonatal rib orientation
  • Lungs at birth collapsed and fluid-filled - replaced with air by powerful inspiratory movement and absorption through the alveoli
  • Lung epithelia has to rapidly change from its prenatal secretory function to that of fluid absorption.
    • initiated by a late fetal change in alveolar epithelial cell (AEC) chloride and fluid secretion to sodium and fluid absorption.
    • absorption requires sodium-potassium ATPase (Na-K-ATPase) together with apical sodium entry mechanisms (Epithelial Sodium Channels, ENaC)
    • Fetal thyroid hormone is thought to have a hormonal role in this developmental switch
  • These changes and pressure also lead to the pulmonary sytem becoming activated and changes in the circulatory shunting that existed before birth.
  • During the late fetal period regular fetal breathing movements (FBM) also occur preparing both the skeletomuscular system and lungs mechanically for respiration.
  • Respiratory Rate is higher than adult (30 breaths/minute).
  • Rib Orientation - Infant rib is virtually horizontal, allowing diaphragmatic breathing only. Adult rib orientation is oblique (both anterior and lateral views), allows for pump-handle and bucket handle types of inspiration.

Links: Respiratory System Development | Postnatal Development - Respiratory

Cardiovascular

  • Umbilical Vasculature - The umbilical blood vessel cavity is lost postnatally over the course of weeks to months after birth. The adult anatomical remnant of the umbilical vein between the umbilicus and liver is the ligamentum teres.
  • Foramen Ovale - two separate forms of foramen ovale closure; functional and structural. Functional closure begins at the first breath and is rapid. Structural (anatomical) closure is much slower and generally occurs before the end of the first year.
  • Ductus Arteriosus - a direct connection between the pulmonary trunk and the dorsal aorta. Postnatal closure occurs initially by by smooth muscle contraction and begins at the first breath and is rapid, completed within the first day (about 15 hr after birth). Anatomical closure is much slower occuring by 2–3 weeks after birth (33% of infants), by 2 months (90% of infants) and by 1 year (99% of infants). The adult anatomical remnant of the ductus arteriosus is the ligamentum arteriosum.
  • Ductus Venosus - connects portal and umbilical blood to the inferior vena cava. Functional closure occurs postnatally within hours. Structural closure commences days after birth and completes by 18 to 20 days. The adult anatomical remnant of the ductus venosus is the ligamentum venosum (a dorsal fissure on the liver).

Neonatal Testing

Apgar Test

Apgar Test

A historic neonatal test designed by Dr Virginia Apgar used in nearly all maternity clinics to assess the newborn infants well being assigned scores for each of 5 indicators: Heart Rate, Respiratory Effort, Reflex Irritability, Muscle Tone, Colour Measured at one and five minutes after birth the Score values are totalled for all indicators: 7-10 is considered normal, 4-7 may require resuscitative measures, 3 and below require immediate resuscitation. In recent years there has been some controversy of the relevance and accuracy of some of the criteria used in this test, though many feel it is still an invaluable initial assessment tool particularly where medical services are limited.

  • Measured at one and five minutes after birth.
  • The Score values are totalled for all indicators
    • 7 to 10 is considered normal
    • 4 to 7 may require resuscitative measures
    • 3 and below require immediate resuscitation
Indicator Score 0 Score 1 Score 2
Activity
(muscle tone)
Limp; no movement Some flexion of arms and legs Active motion
Pulse
(heart rate)
No heart rate Fewer than 100 beats per minute At least 100 beats per minute
Grimace
(reflex response)
No response to airways being suctioned Grimace during suctioning Grimace and pull away, cough, or sneeze during suctioning
Appearance
(color)
The baby's whole body is completely bluish-gray or pale Good color in body with bluish hands or feet Good color all over
Respiration
(breathing)
Not breathing Weak cry; may sound like whimpering, slow or irregular breathing Good, strong cry; normal rate and effort of breathing


Reference: Apgar, V. A proposal for a new method of evaluation of the newborn infant. Curr Res Anesth Analg. 1953 Jul-Aug;32(4):260-7. PMID:13083014

Links: Apgar test

Guthrie Test

Guthrie card

A blood screening test developed by Dr Robert Guthrie (1916-95) at University of Buffalo. The test is carried out on neonatal (newborn) blood detecting markers for a variety of known disorders (phenylketonuria (PKU), hypothyroidism and cystic fibrosis). In NSW and Victoria, the Guthrie Cards are currently stored indefinitely.

Guthrie R, Susi A (September 1963). "A simple Phenylalanine method for detecting Phenylketonuria in large populations of newborn infants". Pediatrics 32: 338–43. PMID 14063511.

Links: Guthrie test


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Practical 12: Embryo to Fetus | Second Trimester | Third Trimester | Birth | Neonatal | Abnormalities


Additional Information

Links: Birth | Postnatal Development | Puberty Development | original neonatal page | original puberty page

Glossary Links

Glossary: A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | Numbers | Symbols | Term Link
2010 BGD: Lecture 1 | Lecture 2 | Practical 3 | Practical 6 | Practical 12

Cite this page: Hill, M.A. (2019, December 11) Embryology 2010 BGD Practical 12 - Neonatal. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/2010_BGD_Practical_12_-_Neonatal

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© Dr Mark Hill 2019, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G