Cervical Ripening
INTRODUCTION:
- Cervical Ripening is a series of complex biochemical changes in the cervix which is mediated by the hormones.
- There is alteration of both cervical collagen and ground substance.
- Ultimately, the cervix becomes soft and pliable
METHODS:
Pharmacological Methods:
- Prostaglandins (PGs)
- Dinoprostone (PGE2 – 0.5 mg): Gel( gold standard), tablet, suppository
- Misoprostol (PGE1:25 μg every 4 hrs in 1st trimester MTP): Tablets(transvaginally or orally)
- Oxytocin
- Progesterone receptor antagonists
- Mifepristone (RU 486)1st trimester MTP
- Relaxin: a protein hormone from corpus luteum, dissolutes cervical connective tissue
- Hyaluronic acid
- Estrogen
Nonpharmacological Methods:
- Stripping the membranes
- Amniotomy (artificial rupture of the membranes)
- Mechanical dilators, osmotic dilators (laminaria)
- Transcervical balloon catheter
- Extra-amniotic saline infusion
Bishop score:
- An attempt to quantify how likely the cervix is to respond to induction efforts
- Dilatation >effacement>station
- Unfavorable: score
- Ripening agent indicated
- Favorable: score >8
- Can induce
- Probability of vaginal delivery with spontaneous labor equals probability of vaginal delivery with IOL
| Parameters | SCORE | |||
| 0 | 1 | 2 | 3 | |
| Cervix Dilatation (cm) | Closed | 1–2 | 3–4 | 5 + |
| Effacement (%) | 0-30 | 40-50 | 60-70 | ≥80 |
| Consistency | Firm | Medium | Soft | – |
| Position | Posterior | Midline | Anterior | – |
| Head: Station | –3 | –2 | –1,0 | + 1, + 2 |
| Total score = 13; Favorable score = 6-13; Unfavorable score = 0-5 | ||||
| Cervical length (cm) | > 4 | 2-4 | 1-2 | < 1 |
Prostaglandins:
- PGE2 is primarily important for cervical ripening that is collagenolytic & also sensitizes the myometrium to oxytocin
- PGF2α for myometrial contraction
- Total 6–8 doses are used
Oxytocin
Acts :
- Receptor mediation
- Voltage-mediated calcium channels
- Prostaglandin production.
- Because of short half life (3–4 minutes) plasma levels fall rapidly when intravenous infusion is stopped
- Oxytocin is effective for induction of labor when the cervix is ripe. It is less effective as a cervical ripening agent.
Mifepristone
- Blocks both progesterone and glucocorticoid receptors.
- RU 486, 200 mg vaginally daily for 2 days has been found to ripen the cervix and to induce labor.
- Onapristone is more selective progesterone receptor antagonists.
SURGICAL INDUCTION:
METHODS:
- Artificial rupture of the membranes (ARM)
- Stripping the membranes
LOW RUPTURE OF THE MEMBRANES (LRM):
- Membranes overlying the internal os are ruptured to drain some amount of amniotic fluid
Contraindication:
- Chronic hydramnios
- Sudden uterine decompression
Procedures:
- FHR monitored
- Lithotomy position
- Two fingers are introduced into the vagina
- Index Finger is passed through the cervical canal beyond the internal os making membranes free from lower segment
- Kocher’s forceps is introduced along
- Blades are opened to seize the membranes and are torn by twisting movements
- Amnihook scratch over the membranes followed by visible escape of amniotic fluid.
After the membranes rupture assesment done for:
- Color of amniotic fluid
- Status of cervix
- Detection of cord prolapse
- FHR pattern
- A sterile vulval pad is placed. Prophylactic antibiotic may be prescribed
Hazards:
- Cord prolapse
- Uncontrolled escape of amniotic fluid and placental abruption
- Injury to the cervix
- Rupture of vasa previa
- Amnionitis
STRIPPING THE MEMBRANES:
- Digital separation of the chorioamniotic membranes from the wall of the cervix and lower uterine segment.
- Criteria:
- Fetal head must be well applied to cervix
- Cervix should be dilated so as to allow introduction of examiner’s finger
Dilators:
- Act by release of endogenous prostaglandins from the membranes and maternal decidua to induce labor and cervical ripening.
- Hygroscopic dilators, e.g. laminaria (desiccated seaweed)(1st trimester MTP), lamicel (magnesium sulfate in polyvinyl alcohol) act by absorption of water.
- They swell and forcibly dilate the cervix.
- Mechanical dilators are as safe and effective as PGE2 in cervical ripening
Transcervical Balloon Catheter:
- Foley catheter and extra-amniotic saline infusion is effective for cervical ripening.
Exam Question
- Mifepristone is an antiprogestin agent used in Cervical ripening
- RU 486 is used in Cervical ripening
- Prostaglandin E2, Progesteron,Oxytocine & Misoprostol are used for cervical ripening during pregnancy
- Induction of abortion is best by PGE2 gel
- Laminaria tent & Mifepristone & misoprostol are used in Ist trimester MTP
- Laminaria tent is made from seaweed
- Laminaria tent is used for the dilatation of the cervix
- Laminaria tent has got a thread to facilitate removal
- Bishops score includes Dilatation ,Effacement,Softening of cervix & Station of head
- Bishop scoring of more than 6 indicates labour has begun
- Prostaglandin tablet methods for induction of labour should not be used in patient with previous lower segment caesarean section
- Bishop’s classification is used for Requirement of induction for labour
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