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uterine contraction (Uterine activity (Improper contractile activity…
uterine contraction
Uterine activity
-
Montevideo units
- Uterine contractile activity measurement units
- Difference between peak contraction strenght and basic tension
- Active contraction space is defined as ratio of pressure during contraction (in mmHg per 10 min.) and the number of contractions
- Alvareza contractions – about 25 Montevideo units
- 100-120 units predict labor onset
- calculated by subtracting the baseline uterine pressure (8-12 mmHg) from the peak contraction pressure for each contraction in a 10-minute period.
- The pressure generated for each contraction is added and for normal labour should be greater than 200
-
During a contraction we assess:
1. Basic tonus of the uterine muscle
2. Contraction amplitude (force)
3. How long a contraction lasts
4. How frequent the contractions are
- can be quantified either by the use of Montevideo units or by the computer calculation of the area under the contraction wave as measured by tocography.
- Progress in normal labour depends on uterine polarity associated with fundal dominance and progressive cervical dilatation.
normal labor
- Contractions start in dilatation period (I stage of labor), contractions appear:
at the beginning every 10-15 minutes, regularly
later every 3-5 minutes, lasting 30 seconds or a little longer, intrauterine pressure 5.3- 6.7 kPa,
- The II stage, „pushing”: every 3-4 minutes, intrauterine pressure of 8 kPa
duration
- Stage I:
in primipara 18 hours, in multipara 12 hours
-
Shoulder dystocia
- Occurrence:
!> 4000g - 2 %
!> 4500g - 10 %
!> 5000g - 40 %
Unfavourable labour progress after the head has been delivered after an incomplete shoulder rotation.
- Risk factors before the labour:
Foetal macrosomia: weight >4500g
history of shoulder dystocia
Pelvic malformations
Maternal obesity BMI >30
Multipara
The age of the mother >40 years old
weight gain during pregnancy >20kg
Post-term pregnancy
AC >HC in ultrasonography
Previous deliveries of newborns with macrosomia
- Intrapartum risk factors:
Prolonged first stage of labour
Prolonged second stage of labour
Induction of uterine contractions
management
- HELPERR:
H – all for Help
E – Episiotomy
L – Legs (Flexing the legs McRoberts maneuver)
P – suprapubic Pressure
E – Enter maneuvers (Wood's Corkscrew Maneuver)
R – Remove the posterior arm
R – Roll the patient
- algorithm:
Calling for an experienced obstetrician
Applying Foley's catheter
Removing the mucus from the oral and nasal cavity of the infant
Applying external maneuvers: McRobert-Gonik's, Rubin
Not pulling the head too strongly, do not apply Kristeller maneuver
Wide episiotomy
Applying internal maneuvers: Wood's, DeLee Pinard, Gaskin, Zavanelli
- Maternal complications
:
Haemorrhage after the delivery
Rectovaginal fistula
Symphysis pubis dysfunction
Uterine rupture
Injuries of the uterine cervix, vagina or perineum
Damaged urinary bladder
Endometritis
Puerperal fever
In rare cases: C-section, transfusions, hysterectomy
- Foetal complications:
Brachial plexus injury
Phrenic nerve injury -causing difficulties in breathing, it may be a cause of a reduced volume of the lungs, remittent pneumonia, chronic gastroesophageal reflux
Clavicle fracture 15%
Humerus fracture <1%
Breaking of the sternocleidomastoid muscle attachment
Cervical spinal cord injuries
Asphyxia. Death.
Contractions
Estrogens
- Growth of muscle cells
- Unblocking of contractile mechanisms
- Decrease the progesterone activity
- Rise in α-receptors activity
- Release of oxytocin & prostaglandines
Progesterone
- Necessary to support pregnancy
- Hyperpolarization of muscle cell
- Lowers the excitability and conductivity
of impulses
- Causes domination of β-receptors
Oxytocin
- Hypothalamus --> hypophysis posteriori lobe
- Stimulates the contractile activity of myometrium
- Activity augmented by estrogens and diminished by progesterone
- Influence of mechanical factor
- Excretion risen by stimulation of breast nipples
- Blocked by oxytocinase
oxytocinase
- Produced by syncytiotrophoblast cells
- Level correlates with the placental mass, fetal body mass and placental competence
- Lowered production in pregnancy complicated by diabetes and by hypertension
- CAP (cystaminopeptydase) – laboratory monitoring
Prostaglandins
- PGE1, PGE2, PGF2α
- Stimulates excretion of oxytocin
- Causes disintegration of progesterone
Mechanical factors
- Distension of uterine muscle - PGF2α
- Mechanical stimulation od cervix
- Higher oxytocin excretion
- Spine reflex
Cervical dystocia
- Malfunctioning of one of the following mechanisms (more frequent in primagravidas):
- Uterine muscular fibre retraction
- Active diastole of the involuntary muscle fibres in the uterine cervix
- The pressure exerted by the foetal head
- Hydrodynamic influence of the lower pole of the urinary bladder.
-
Management:
On-going assessment of the progress of labour – uterine cervix dilation, uterine contractions and the lowering of the presenting part in the birth canal
Epidural administration
C –section
Uterus
- Labor contractions cause differentiation into:
Active part – uterine corpus
Passive part – „lower segment”
(cervix + lower part of corpus)
Bandl brim
- The border between the active and the passive part of the uterus
- Found in palpation above pubic symphysis
- Transverse course
- Oblique course in imminent uterine rupture
-
Alvarez contractions
- Uncoordinated contractile activity
- Low amplitude
- Low strenght
- First contractions in pregnancy
- From ca 20th week of gestational age
-
Bishop score
- Effacement
- Cervix position
- Consistency
- Dilation
- Presenting part station in the birth canal
Labor onset
- Regular and augmenting contractile uterine activity
- Amniotic fluid leakage (rupture of membranes)
Delivery
- Phases:
slow – unsynchronized contractions (up to 2 cm – 6 h)
acceleration (up to 4 cm – 2 h)
quick (up to 8 cm – 1,5 h)
retardation
Postpartum contractions
- Deacreasing contractions for 12h – every 10-15 min.
- Corpus contractions - Blood vessels occlusion – protection against bleeding
- Cervix contractions – cervix formation
