Laplace's Law Dictates the Timing of Birth, the Duration of Pregnancy, and the Mode of Delivery Through Exponential Uterine Wall Tension and Hormonal Milieu, as Well as Their Light- Dark Cycle Modulation: A Hypothesis
Hegazy, Ali
Background: The laws of physics govern the functions of human body
organs. However, the law of physics that controls uterine function during
pregnancy remains unknown. Spontaneous preterm labor, labor dystocia,
and post-term pregnancy are significant obstetric complications, and their
biological mechanisms are poorly understood. A failure to understand
uterine function during pregnancy is a major shortcoming in modern
healthcare.
Objective: Supporting the hypothesis, Laplace's Law dictates the timing
of birth, the duration of pregnancy, and the mode of delivery through
exponential uterine wall tension and hormonal milieu, as well as their
light-dark cycle modulation. We will refer to this hypothesis as Hegazy's
Hypothesis for Gestation (HHG).
Method: A literature search was conducted using Medical Subject
Headings terms on every topic of the hypothesis in PubMed, in addition to
manually searching for additional references. The scripts that were found
were reviewed, examined, and condensed, along with two 40-second 3D
animations.
Results: The anatomical existence of the isthmus of the cervix
should be reconsidered, as there has been no convincing evidence to
support its existence since Aschoff first proposed it in 1905. Uterine
mechanotransduction may be the primary mechanism and system that
controls uterine function during pregnancy through exponential uterine
wall tension (EUWT) and the hormonal milieu. EUWT has anatomical
and functional components, determinants, modulators, and a physiological
mechanotransduction effect. EUWT is created and maintained by
the complex interaction between the gestational sac, uterus, and
cervix, whose primary function is the maintenance of EUWT. EUWT
mechanotransduction with progesterone/estrogen modulation induces
the stretch-dependent inhibitory uterine system (SDIUS). The SDIUS
is the primary system that maintains pregnancy through autonomic
intrinsic myometrial cell characteristics (AIMCC). AIMCC enables the
uterus to control its function autonomously and intrinsically, due to the
Myometrial Tension-Contraction Interaction (MTCI) characteristic, where
high tension induces relaxation and low tension induces contraction.
EUWT mechanotransduction with progesterone/estrogen modulation also
induces the stimulatory system by inducing myometrial hyperplasia and
hypertrophy. Embryologically and evolutionarily, the uterus is composed
of two uteri. Uterine contractions (stimulatory system) create direct and indirect uterine-cervical interactions (DIDUCI). DIDUCI
transforms the cervix into the lower uterine segment
(LUS), through the TYVU pattern formation. Lightdark
cycle modulation of the interactive inhibitory and
stimulatory systems divides gestation into five clinical
phases: growth, maturation, transition, parturition, and
involution. Maturation phase (32-40 weeks): Nocturnally,
oxytocin and melatonin modulate the stimulatory system.
Additionally, cortisol modulates the inhibitory system,
causing a transient nocturnal pause. The nocturnal
synchronization and synergy of the two systems make the
uterus an active organ at night, transforming the cervix
into the LUS. This ultimately leads to nocturnal EUWT
and SDUIS failure, dictating both pregnancy intervals
and circadian timers. The successful transformation
of the cervix into the LUS during late pregnancy is the
cornerstone of pregnancy termination and achieving
successful labor. The failure of this mechanism alone
causes post-term pregnancy; if combined with the failure
of the inhibitory system, it results in labor dystocia. A
malfunction in the inhibitory system causes preterm labor.
Conclusions: Pregnancy is in a state of balance between
the opposing and interactive inhibitory and stimulatory
systems, secondary to EUWT mechano-transduction
and progesterone/estrogen modulation. The autonomous
creation, maintenance, and eventual termination of EUWT,
secondary to light-dark cycle modulation, make gestation
an autonomic cycle with constant intervals and circadian
timers, where EUWT malfunctions alter birth timing,
pregnancy duration, and mode of delivery. Laplace's law
measures EUWT which may be the law of physics that
govern uterine function during pregnancy.
↧