The Perinatal Period: Transition from the Womb

1. The Perinatal Period: Transition from the Womb

3. Birth as a “non-event” Neuro-behavioral systems functional prior to birth develop in anticipation of need “forward reference” of Weiss or “environment expectant” For example, sucking swallowing “respiration” hiccups yawning So, other than constraints imposed by the intra-uterine environment (e.g. fetuses cannot cry without air), there is little behavioral difference between a late-term fetus and a newborn

4. What distinguishes a newborn from a fetus is that these behaviors are NECESSARY for survival For example, “breathing” is not functional as respiration in the fetus, but is essential to the newborn. How is initiation of breathing assured? 1. Temperature change is a noxious stimulus • Anoxia produced by clamping umbilical cord 3. Fluid is expelled from lungs during delivery, the remainder quickly absorbed. 4. Changes in other sensory inputs Spanking a newborn is not necessary to initiate breathing, and birthing in warm water makes little sense from either a physiological or evolutionary perspective.

5. Similarly, sucking and swallowing are essential to the newborn, but have been expressed by the fetus. About the only thing not apparent in the fetus that is expressed by the newborn is crying, which we will discuss later. So from a neuro-behavioral perspective, birth really is a “non-event,” unlike, for example amphibian metamorphosis.

6. What about from a biological/comparative perspective? Are there biological markers of maturity that define birth?

7. What initiates birth? Mother? Fetus? What is the signal? Oxytocin stimulates uterine contractions, but what stimulates oxytocin release?

8. What initiates birth? Surfactant Protein A (SF-A) Production in mice begins at G17 d (birth at G19) begins in humans ~G32 wk (birth at 40 wk) “breathing” amniotic fluid releases SF-A into the fluid SF-A is essential for respiration after birth SF-A signals mother that fetal lungs are mature, stimulates labor

9. Other than the capacity for independent respiration, there is little relationship between maturity and birth/hatching.

16. Altricial born in a relatively immature state Precocial born in a relatively mature state

19. CAUDATE CORTEX CEREBELLUM THALAMUS MEDULLA MIDBRAIN MIDBRAIN CEREBELLUM THALAMUS CAUDATE MEDULLA CORTEX

22. Bignall, K.E. (1974) Experimental Neurology, 42, 566-573.