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Physiology and Pathology of Uterine Contractions
Michael G. Halaška, M.D.Department of Obstetrics and Gynaecology
of 2nd Medical Faculty
Physiology
myometrium – smooth muscle
enlargment of the muscle cells
basal tonus
first contractions from 20thweek of gravidity
Braxton-Hick contractions
Physiology
Montevid Units
Montevid Units – addition of amlitudes of contractions in 10 minutes pacemaker – contraction wave – 2cm/samplitude of an contraction 1st stage – 40-60 mm Hg 2nd stage – 80 mm Hg
closure of blood-vessels veins : 20 mm Hg artery: 60 mm Hg
Physiology
basal tonus 10 mm Hg
1. stage of labour 30-40 mm Hg - 120 MU
2. stage of labour 50-60 mm Hg - 250 MU
resting time >30 s
Physiology
Proper shape of the contractions 1. stage
2. stage
3. stage
Physiology – starting factors
1. mechanical - ↑ pressure, ↓ volume
2. endocrine estrogen - ↑ number of estro receptors,
↓ membrane potential, ↑ ATP in myocytes oxytocine - ↓ membrane potential, ↑ PG prostaglandins – preparing of cervix, contract.
3. neurogen Fergusson reflex Parasympaticus reflex
Recording the contractions
absolute – intrauterine
- intrauterine catheter
relative – external
- using piesoelectric
effect
Indications and contraindications
Type of sensor
Conditions Indications Contraindications
External anytime
non-ivasive
as CTG none
not recommended
- obesity
Internal cervix dilatated at least 2-3 cm,
ruptured membranes,
tonus of the uterus
mostly scientific use
placenta praevia,
face presentation,
intraovulatory infection
Pathology
1. hypertonus
2. hyperactivity
3. hypoactivity
4. dystokia
5. failure of the abdominal muscle
Pathology
1. hypertonus
2. hyperactivity
3. hypoactivity
4. dystokia
5. failure of the abdominal muscle
Pathology - hypertonus
etiology: macrosomy, multiple pregnancy,
premature separation of placenta
pathophysiology: ↑ basal tonus - ↑blood in veins – hypoxy
clinics: palpable,
changes on CTG
treatment:
tocolysis
Pathology
1. hypertonus
2. hyperactivity
3. hypoactivity
4. dystokia
5. failure of the abdominal muscle
Pathology - hyperactivity
> 390 MU, >7 contrac/min, resting time <30 s
etiology: hypersensitivity, overstimulation of the uterus
clinics: CTG changes
therapy: less oxytocine, tocolysis
Pathology
1. hypertonus
2. hyperactivity
3. hypoactivity
4. dystokia
5. failure of the abdominal muscle
Pathology - hypoactivity
< 100 MU, < 30 mm Hg, < 2 contract/min
type: primary – from the beginning
secondary – during the labour
etiology: primary: hypoplasia of U., dystokia
secondary: prolonged labour, overstimulation by oxytocine, exhaustion of the mother
clinics: CTG, no postup of the labour
therapy: oxytocine, tocolysis, rest
Pathology
1. hypertonus
2. hyperactivity
3. hypoactivity
4. dystokia
5. failure of the abdominal muscle
Pathology - dystokia
etiology: hypertonus of the cervix, failure of pacemakers, exhaustion of
uterus
clinics: CTG, no postup of the labour
therapy: tocolysis, S.C.
Pathology
1. hypertonus
2. hyperactivity
3. hypoactivity
4. dystokia
5. failure of the abdominal muscle
Pathology - failure of abd. muscle
etiology: disease of the muscle or inervation disease which unables higher activity ( heart,
eyes .. ) epidural anesthesia exhaustion of the mother obesity not cooperating mother
therapy: forceps, VEX, S.C.