Inducing labour at term

If labour does not start when you would like it to, you may be able to start it. If it is going too slowly, you can speed it up. So distinguish between: (1) the induction of labour (the subject of this section) when the patient is not in labour, or only in the latent phase, and (2) the acceleration of labour, when she is in the active phase with her cervix more than 3 cm dilated. Here we are concerned with induction. For acceleration see M 22.2.

If the continuation of pregnancy would be harmful to a mother or to her baby, and especially if either of them is in danger of death, the logical solution might seem to be to induce labour and deliver them. Unfortunately, induction has its risks for both of them, so there are few indications for doing it in a district hospital. The commonest one is probably proven rupture of the membranes (19.5) lasting more than 12[nd]24 hours, when she is near term ([mt]37 weeks). All the other indications below are rare and relative.

Artificial rupture of the membranes (ARM), with an oxytocin drip or oral prostaglandins, is the most powerful way of inducing labour. Don't do it for minor indications, because: (1) You may introduce infection when you rupture her membranes. If labour starts soon, the risk is small, but if it is delayed, the risk is large, especially if the baby is dead. Minimize this by taking the most careful aseptic precautions. (2) If you try to induce her too soon: (a) he will be immature and have less chance of surviving, and (b) her labour is unlikely to start, and if it does start, it may so slow that you have to section her. So only induce labour, when the balance of risks favours it[md]when the surfactant test shows that he is mature, and Bishop's inducibility test shows that her cervix is ripe, and ready for labour. (3) Inducing labour increases your Caesarean section rate, with all the disadvantages this has (18.1).

There are other risks: (4) Rupturing her membranes may cause the cord to prolapse. (5) Oxytocin may cause her uterus to rupture. And, (6) her placenta may separate. So never induce labour to suit your convenience or hers, but only for the soundest of obstetric reasons.

If her cervix is unfavourable, you can try ripening it with prostaglandins (expensive), or you can insert the balloon of a Foley catheter into her extra-amniotic space (cheap and effective).

INDUCING LABOUR [s8]AT TERM INDICATIONS. (1) Proven rupture of the membranes lasting [mt]12[nd]24 hours when the baby is near term ([mt]37 weeks). (2) Severe pre-eclampsia if the cervix is ripe (17.4). (4) Diabetes (16.3). (5) Abruption (16.3). (6) Postmaturity (19.6) 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.

Dilatation in cm: 0 cm, score nil. 1 cm to 2 cm, score one. 2 cm to 3 cm, score two. 3 cm to 4, cm score three.

Length in cm: 3 cm, score nil. 2 cm, score one. 1 cm, score two. 0 cm, score three.

Station of the head: 5/5, score nil. 4/5, score one. 3/5, score two. 2/5, score three.

Consistency: Firm, score nil. Medium, score one. Soft, score two.

Position of the cervix. Don't confuse this with the position of the presenting part (OA, OP, etc.): Posterior, score nil. In the middle, score one. Anterior, score two.

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 3 mg PGE[,2] dinoprostone (''Prostin E2' Upjohn) tablet in her posterior fornix on the afternoon before you induce labour. Follow this by another 3 mg 6 to 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 PGE[,2] 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 to 18 hours before induction, with careful aseptic precautions, and under direct vision, use a Cusco's speculum to insert a 16 to 24 Ch Foley catheter, with a 30 to 45 ml balloon, into her extra-amniotic space. Inflate this with 30 to 45 ml of sterile water, and leave it in place.

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

OXYTOCIN [s7]TO INDUCE LABOUR AT TERM INDICATIONS. A high risk-factor, particularly for the baby, such as: (1) Diabetes (17.3). (2) Gestational hypertension (17.4). (3) Placental abruption (16.13). (4) An unstable lie (19.9). (5) A dead baby 3 weeks after fetal movements have stopped (16.4). (6) Postmaturity (19.6).

CAUTION ! (1) For all the above indications her cervix must be favourable, by the score given above. (2) This is oxytocin to induce labour at term. It has several other uses, see 16.4 and 18.4a.

CONTRAINDICATIONS. (1) CPD. Never give a multip oxytocin if there is ANY sign of CPD. (2) A previous Caesarean section. (3) Myomectomy. (4) Fetal distress. (5) Malpresentation. (5) Grand multiparity 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 units to 500 ml of 5% dextrose in water at 10 drops a minute. Vials of oxytocin usually contain 5 units, so this is one vial. Watch her closely and increase the drip rate every 30 minutes like this: 10 drops/minute, 20 drops/minute, 40 drops/minute, 60 drops/minute. Increase the infusion until her uterus is contracting 2 or 3 times every 10 minutes. If vaginal examination shows that her cervix is not dilating, increase the infusion to 60 drops/minute regardless of how frequently contractions occur. Don't go above 60 drops/minute.

If you don't get the effect you want and she is a primip, increase the concentration to 10 units in 500 ml and start again at 10 drops/minute.

When her cervix is more than 5 cm, and she is having good contractions, you may be able to reduce the rate of the drip. 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 p.m., stop the drip 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 multip). (2) In a multip, reduce the starting dose to 1 unit, and reduce or stop the drip as soon as regular contractions are established. (3) Assess her uterine contractions carefully. If there is no relaxation between contractions, stop the drip. If there is fetal distress, see ''Stop Press'. (4) Oxytocin in high doses (more than 10 units at 30 drops a minute) has an antidiuretic effect. So beware of ''water intoxication', and see Section 16.4. (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 units 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 [mt]2 l/24 hours without reviewing her carefully.

RUPTURING THE MEMBRANES [s7]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 (19.5). (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 (see above).

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. Section her if it is Type Three or Four (16.12).

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 section her.

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 (A 16.6), 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 (19.10). 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.