Childbirth (paturition) signs of the full-term baby

0.introduction

Parturition is the process by which the fetus, placenta, and Fetal membranes (SFLT) are expelled from the mother’s uterus at the end of pregnancy. From a histological and embryological perspectives, this process represents the coordinated end-point of fetal maturation, placental endocrine changes, and maternal myometrial activation.

A full-term neonate (37–42 weeks) exhibits specific morphological and functional characteristics.

1.Embryological Basis of Parturition

1-1.Fetal endocrine signals

• In late gestation, the fetal adrenaline cortex increases cortisol secretion.
• surfactant synthesis and liver maturation are promoted, placental hormone production ahifted toward estrogen.
• increase fetal DHEA-S enhances placental estrogen output.

1-2. Placental hormone shifts

• estrogen rise near term stimulates;

・Formation of gap junction(onnexin-43) between myometrial cells

・upregulation of oxytocin receptors.

• functional progesterone withdrawal reduces uterine quiescence.
• increased prostaglandins (PGE2, PGF2α) soften the cervix triggering uterine contraction.

1-3.Materna; myometrial activation

• myometrrial smooth muscle becomes moreorganized and excitable.
• Gap junction formation allows synchronized contractillity.
• Ferguston reflex(https://en.wikipedia.org/wiki/Ferguson_reflex); cervix streching →oxytocin released →strnger contractions.
  

2.Histological changes related to parturition

2-1. cervical ripening

• significant remodeling of cervical ECM;

・breakdown and rearrangement of collagen fibers

・increased hyaluronic acid, leading to hydration and softening

• infilttration of neutrophills and macrophages, releasing cytokins and proteases.
• More flexible cervical epithrlium for dilation.

2-2.myometrial adaptations

• Hypertrophied smooth muscle cells rich in actin and myosin filaments
• Increased concentrations of gap junctions facilitates synchronized contractions.
• Hormone-induced increased responsiveness to oxytocin.

2-3.changes in fetal membranes

• Decidua and chorion increase prostaglandin synthesis through activation of phospholipase A₂[1]
• Weakening of membranes for smooth rupture

3.stages of parturition

1st stages - dilation

• cervical softening anf thining(effacent)
• gradual dilation mediated by prostaglandins and mechanical pressure.

2nd stages - fetal expulsion

• Uterine contractions expell fetus.
• fetal skulls sutures and fontanells allow moldings to pass through the birth canal.

3rd stages - placental delivery

• seperation occurs at the decidua basalis.
• placenta and membranes are expelled finally and uterus begins to contract postpartum.

4. signs of full-term baby

4-1.physical features

• Length: ~48–52 cm
• Weight: ~2.5–4.0 kg
• Skin: Smooth, less reddish; thin layer of vernix caseosa
• Lanugo: Mostly shed
• Fat deposition: Well-developed subcutaneous fat for thermoregulation
• Nails: Extend to finger and toe tips
• Ears: Firm cartilage, good recoil

• Cranial sutures: Approximated; normal-sized fontanelles

4-2.respiratory readiness

• Lungs contain adequate Surfactant from mature type II pneumocytes.

• Sufficient alveolar development for gas exchange.

4-3. cardiovuscular adaptations

• functional closure of foramen ovaleDevelopment of the heart)
• Closure of ductus arteriosus and ductus venosus

• Establishment of neonatal circulation

4-4. neurological and behavioral signs

• Good muscle tone
• Regular spontaneous movements
• Strong cry
• Presence of neonatal reflexes:
  • Moro
  • Sucking
  • Rooting
  • Palmar/plantar grasp

4-5. temperature regulation

• sufficient brown adipose tissue allows non-shivering termogenesis.

4-6.gastointestinal and metabolic maturity

• Coordinated swallowing and sucking
• Ability to digest breast milk
• Hepatic function adequate though bilirubin conjugation is still limited

conclusion

Parturition is the culmination of hormonally regulated fetal maturation and structural changes in maternal tissues. Understanding this process at the histological and embryological levels is crucial for recognizing the features of a full-term neonate and ensuring appropriate neonatal care.

Sources

1. Sadler, T. W. Langman’s Medical Embryology. Latest Edition. Lippincott Williams & Wilkins.
2. Junqueira, L. C., & Carneiro, J. Junqueira’s Basic Histology: Text and Atlas. McGraw-Hill.
3. Moore, K. L., Persaud, T. V. N., & Torchia, M. G. The Developing Human: Clinically Oriented Embryology.