INDICATIONS. (1) A patient who has had one lower segment Caesarean section, and the reason for it is absent in this pregnancy. For example, it might have been done for a malposition or malpresentation, maternal or fetal distress, or CPD due to hydrocephalus, etc. (2) The scar from a myomectomy (provided her uterine cavity was not opened during the operation), hysterotomy, or uterine perforation during a ‘D and C’.
CONDITIONS. (1) She must have had not more than one previous Caesarean section. (2) When labour starts, she must either be in hospital, or not more than one hour away from it, with certain access to suitable transport. (3) Caesarean section must be available any time of the day or night, within one hour of the decision to section her. (4) Her pregnancy must have been normal. (5) Her baby must be a vertex presentation in the occipito–anterior position (some obstetricians will do a trial of scar for a breech). (6) There must be no fetal or maternal distress.
CONTRAINDICATIONS. (1) Two or more previous lower segment Caesarean sections. (2) One previous classical Caesarean section. (3) Any degree of CPD, or suspected CPD in this pregnancy, as suggested by a true conjugate of <9 cm or a diagonal conjugate of <11.5 cm. Although this is the ideal figure, it is unrealistic in some countries; in New Guinea, for example, a figure of 10.5 cm is used for the diagonal conjugate. (4) An occipito-posterior presentation. (5) Any other form of malpresentation, or obstetric complication. (6) Sepsis following a previous section is a relative contraindication only. (7) Any need for an oxytocin drip.
A request for tubal ligation favours the decision to do an elective Caesarean section. On its own, it is not a sufficient contraindication to vaginal delivery, because a vaginal delivery followed by tubal ligation will be safer. If a patient arrives in labour, use the same criteria as if she arrived during pregnancy.
ASSESSMENT. See all mothers with a previous section in the antenatal clinic at 36 weeks, and decide whether to do a trial of scar or not. Take a careful history. Assess her pelvis clinically and assess the size of her baby by measuring the height of her fundus; if it is >40 cm, don’t do a trial of scar. If you have not previously measured her true conjugate, X-ray pelvimetry is useful but not essential.
METHOD. Ask her to avoid heavy work during the last month of pregnancy, or to come in for rest. If she can be sure to reach hospital within an hour of labour starting, let her wait at home until labour starts. Otherwise, admit her at 36 weeks for rest and observation. Allow her fluids only by mouth during labour.
Don’t induce labour. Unless your blood bank can be relied upon to have blood available within an hour, have it cross-matched, and ready to give if necessary. Record her pulse and the fetal heart rate carefully.
You may sometimes be able to feel the scar in her lower segment, when you examine her vaginally. This will be easier if you are using epidural anaesthesia. If it bulges or feels weak, section her immediately. The tenderness of a scar is difficult to assess in labour, and is not, on its own, an indication for section. Assist her with outlet forceps, or vacuum extraction, if necessary.
Abandon the trial if: (1) She crosses the alert line on the cervicograph! (2) Her pulse rises to 100. (3) She has pain between contractions. (4) Her pain is generalized. (5) She has unexplained vaginal bleeding. (6) Her uterine contractions cease. (7) She has rectal or vaginal tenesmus.
Stay with her during labour so that you can examine her lower uterine segment vaginally immediately after delivery of the placenta, so as to be sure that it has not ruptured. One contributor considers this impractical, and only recommends it if she has had a PPH; others do it routinely. Examining it is uncomfortable, but does not need anaesthesia. If you find a rupture, repair it at laparotomy (9.2, 18.17).
If she has a postpartum haemorrhage, the scar in her uterus has probably broken open; confirm this by doing a vaginal examination, and repair it abdominally if you find it.
