INDUCING LABOUR AT TERM

INDICATIONS (1) Proven rupture of the membranes lasting > 12 hours when the baby is near term (> 37 weeks). (2) Severe pre-eclampsia if the cervix is ripe (21.3). (4) Diabetes (21.2). (5) Abruption (20.2). (6) Postmaturity (23.5) is an un­certain indication, because the diagnosis is rarely made in district hospital practice.

BISHOP’S INDUCIBILITY SCORE Assess the dilatation of a mother’s cervix, its length, its consistency, its position in relation to the axis of her vagina, and the height of her baby’s head. Work out the score like this: the higher it is, the more likely it is that induction will succeed. The highest score is 13, and a score of 7 or more is favourable for induction.

210ptXllll SCORE 0 1 2 3

Dilation (cm) 0 1–2 2–3 3–4
Length (cm) 3 2 1 0
Station
of the head 5/5 4/5 3/5 2/5
Consistency Firm Medium Soft
Position
of cervix Post. Middle Ant.

Don’t confuse Position of the cervix. with the position of the presenting part (OA, OP, etc.).

RIPENING A CERVIX

INDICATIONS (1) When the cervix is not sufficiently ripe to enable you to rupture the membranes to induce labour. After ripening, labour will often start without any need to rupture the membranes. See also Section 16.4.

METHODS Here are three ways of ripening a cervix:

A dinoprostone vaginal tablet in her posterior fornix. Insert one 3mg PGE2 Dinoprostone tablet in her posterior fornix on the afternoon before you induce labour. Follow this by another 3mg 6–8 hours later if labour is not established, and then, if necessary, a further one, to a maximum of 3.

CAUTION! (1) The tablet must be close to her cervix in her posterior fornix; merely slipping one into her introitus does not work. (2) Avoid prostaglandins if she is para 5 or above. There may be hyperstimulation. (3) Observe her carefully for at least 2 hours.

A dinoprostone tablet in her cervix. Insert a 0.5 mg PGE2 oral tablet into her cervical canal. Repeat this 6-hourly up to 4 doses.

A Foley catheter in the extra-amniotic space is useful if you have no prostaglandins. 12–18 hours before induction, with careful aseptic precautions, and under direct vision, use a Cusco’s speculum to insert a 16–24 Ch Foley catheter, with a 30-45mL balloon, into her extra-amniotic space. Inflate this with 30–45 ml of sterile water, and leave it in place.

CAUTION! Whenever you induce labour, monitor the baby carefully.

OXYTOCIN TO INDUCE LABOUR AT TERM

For other uses see 22.6.

INDICATIONS A high risk-factor, particularly for the baby, such as: (1) Diabetes (21.2). (2) Gestational hypertension (21.3). (3) Placental abruption (20.11). (4) An unstable lie (23.8). (5) A dead baby 3 weeks after fetal movements have stopped (20.3). (6) Postmaturity (23.5).

CAUTION! For all the above indications her cervix must be favourable, by the score given above.

CONTRAINDICATIONS (1) CPD. Never give a multipara oxytocin if there is ANY sign of CPD. (2) A previous Caesarean section. (3) Myomectomy. (4) Fetal distress. (5) Malpresentation. (5) Grand multiparaarity is a relative contraindication, but you can cautiously give a lower dose. (6) Placenta praevia.

METHOD Check the baby’s lie and presentation, and try to make sure that one nurse stays with her all the time. Start in the morning with a dose of 5 U to 500 ml 5% dextrose in water at 10 drops/min. Vials of oxytocin usually contain 5 U, so this is one vial. Watch her closely and increase the IV rate every 30 min like this: 10 drops/min, 20 drops/min, 40 drops/min, 60 drops/min. Increase the infusion until her uterus is contracting 2 or 3 times every 10 mins. If vaginal examination shows that her cervix is not dilating, increase the infusion to 60 drops/min regardless of how frequently contractions occur. Don’t go above 60 drops/min.

If you don’t get the effect you want and she is a primipara, increase the concentration to 10 U in 500 ml and start again at 10 drops/min.

When her cervix is >5 cm, and she is having good contractions, you may be able to reduce the rate of the IV. Do this gradually. If they go off, increase it again.

If her membranes have not ruptured, and she has not gone into labour by 7 pm, stop the IV and try again in the morning. If her membranes have ruptured, induction must not stop.

CAUTION! (1) Higher doses than these increase the uterine tone between contractions, and thus impair the placental circulation. Palpation does not detect this increased tone, unless it is gross. Too much oxytocin will cause prolonged tetanic contractions, and may rupture her uterus (especially if she is a multiparaara). (2) In a multiparaara, reduce the starting dose to 1 unit, and reduce or stop the IV as soon as regular contractions are established. (3) Assess her uterine contractions carefully. If there is no relaxation between contractions, stop the IV. (4) Oxytocin in high doses (>10 U at 30 drops/min) has an antidiuretic effect. So beware of ‘water intoxication’ (20.3). (5) If she is not delivered but is contracting satisfactorily and progressing well, you can use up to 2 l of a solution of 10 U in 500 ml. With more than this volume there is a risk of water intoxication. If she is not nearly delivered, consider Caesarean section. (6) Don’t give her >2 l/24 hours without reviewing her carefully.

RUPTURING THE MEMBRANES TO INDUCE LABOUR

CONTRAINDICATIONS (1) A high mobile head (the cord may prolapse). (2) A dead baby (except in abruption; she will labour fast), because he is much more easily infected (23.4). (3) If she has hydramnios, start by withdrawing some amniotic fluid from her abdomen, so as to reduce her uterus to a normal size. The sudden release of much fluid can precipitate abruption, and make malpresentations, such as a shoulder presentation, more likely.

METHOD Make sure her bladder is empty. Check the fetal heart, put her into the the lithotomy position, and use careful aseptic precautions.

Flood her vulva with antiseptic solution. Wearing sterile gloves, do a careful vaginal examination and measure Bishop’s score.

Spread her labia widely, put two fingers into her vagina and then into her cervix. If necessary, stretch it to admit your 2 fingers. Gently sweep her membranes away from her lower segment without rupturing them. Feel carefully for the placenta, or the cord.

If you can feel her placenta, she has placenta praevia and you have made a horrible mistake. You are unlikely to do this if the head was in contact with the brim. Do a Caesarean section if it is Type Three or Four (20.11).

If you can feel the cord presenting through her membranes, leave them intact, turn her on her side and repeat the examination in about 2 hours. With luck, the cord will have floated away. If it has not and you want a live baby, you will have to do a Caesarean section.

CAUTION! If she is in labour, rupture her membranes during a contraction, to minimize the risk of prolapse of the cord.

If you cannot feel either the placenta or the cord presenting through her membranes, rupture them with Kocher’s forceps. Hold these in your left hand, and guide them through her cervix with your right hand. As you prepare to tear them, ask an assistant to push the presenting part into her pelvis. This will allow the fluid to escape in a controlled way, and will minimize the risk of the cord prolapsing. Grip her membranes and tear them. If fluid flows, or there is fetal hair in your forceps, you have succeeded. Note the amount and colour of her amniotic fluid, make sure the cord has not prolapsed, and check the fetal heart.

Enlarge the opening with your fingers. Keep them in her vagina until the head has descended against her cervix. With your fingers still in her vagina, check the fetal heart again. If she has a sudden persistent bradycardia: (1) She may have the supine hypotensive syndrome, so turn her on her side. (2) The cord may be trapped. Don’t raise the baby’s head, because the cord will probably prolapse further (23.9). Instead, turn her on her side and listen again; this usually solves the problem.

Alternatively, do a ‘membrane sweep’ only, and don’t rupture her membranes until she is well advanced in labour. This is effective, and there is less risk of infection than when her membranes are ruptured some time before delivery.