Classical caesarean section in preterm deliveries

Risk factors for classical hysterotomy by gestational age

OBJECTIVE

To examine the likelihood of classical hysterotomy across preterm gestational ages and to identify factors that increase its occurrence.

METHODS

This is a secondary analysis of a prospective observational cohort collected by the Maternal-Fetal Medicine Network of all women with singleton gestations who underwent a cesarean delivery with a known hysterotomy. Comparisons were made based on gestational age. Factors thought to influence hysterotomy type were studied, including maternal age, body mass index, parity, birth weight, small for gestational age (SGA) status, fetal presentation, labor preceding delivery, and emergent delivery.

RESULTS

Approximately 36,000 women were eligible for analysis, of whom 34,454 (95.7%) underwent low transverse hysterotomy and 1,562 (4.3%) underwent classical hysterotomy. The median gestational age of women undergoing a classical hysterotomy was 32 weeks and the incidence peaked between 24 0/7 weeks and 25 6/7 weeks (53.2%), declining with each additional week of gestation thereafter (P for trend <.001). In multivariable regression, the likelihood of classical hysterotomy was increased with SGA (n=258; odds ratio [OR] 2.71; confidence interval [CI] 1.78-4.13), birth weight 1,000 g or less (n=467; OR 1.51; CI 1.03-2.24), and noncephalic presentation (n=783; OR 2.03; CI 1.52-2.72). The likelihood of classical hysterotomy was decreased between 23 0/7 and 27 6/7 weeks of gestation and after 32 weeks of gestation when labor preceded delivery, and increased between 28 0/7 and 31 6/7 weeks of gestation and after 32 weeks of gestation by multiparity and previous cesarean delivery. Emergent delivery did not predict classical hysterotomy.

CONCLUSIONS

Fifty percent of women at 23-26 weeks of gestation who undergo cesarean delivery have a classical hysterotomy, and the risk declines steadily thereafter. This likelihood is increased by fetal factors, especially SGA and noncephalic presentation.

LEVEL OF EVIDENCE

: II.

The relationship between gestational age and the incidence of classical caesarean section

Improved neonatal survival has led to a rise in the number of Caesarean sections being performed in the presence of extreme prematurity. Many of these operations require an incision in the upper uterine segment with consequent ramifications for the management of any subsequent pregnancy. In this analysis of obstetric patients in a tertiary referral institution over a 9-year period, there was an overall Caesarean section rate of 18%. A classical incision was performed in 1% of all caesarean sections, but at 24 weeks' gestation, 20% of Caesarean sections were 'classical'. This frequency decreased to less than 5% at 30 weeks and less than 1% from 34 weeks' gestation. Most women having a classical Caesarean section at term had either a transverse lie or a major degree of placenta praevia.

Uterine incision and maternal blood loss in preterm caesarean section

The purpose of this study was to compare maternal blood loss, as reflected by the perioperative changes in haemoglobin (Hgb), the incidence of severe bleeding (estimated blood loss > 1000 ml) at operation, and the need for blood transfusion, between patients who had classical caesarean section (CCS) and lower segment caesarean section (LSCS) at 34 weeks gestation or less. The data from 31 women delivered by CSS between 25 and 34 weeks gestation were compared, in a retrospective case-control fashion, to another 31 women delivered by LSCS. Patients were matched for gestational age at delivery, the type of anaesthesia, and the prior use of tocolytic therapy. Excluded from the study were patients who had an antepartum haemorrhage or placenta praevia. There was a significantly greater reduction in maternal Hgb and an higher incidence of severe bleeding in the CSS group compared to the LSCS group (P < 0.05). The results of this study suggest that for preterm caesarean sections, the classical incision is associated with increased blood loss compared to the lower segment incision.

Classical versus low-segment transverse incision for preterm caesarean section: maternal complications and outcome of subsequent pregnancies

In a retrospective, controlled, follow-up study of 326 women who had a primary preterm caesarean section, the risks of postoperative maternal morbidity and uterine rupture or dehiscence in subsequent pregnancies were investigated in relation to the mode of incision (classical compared with low-segment transverse incision). The classical incision was associated with a higher frequency of postpartum fever in the immediate postoperative period (16% compared with 6%, P less than 0.01). Of the 326 patients reviewed 286 (88%) were contacted for information about subsequent pregnancies. Information was obtained for 70 pregnancies subsequent to a classical caesarean section, and 71 pregnancies subsequent to a low-segment transverse caesarean section, which had continued for more than 20 weeks gestation. Of the pregnancies after the classical operation 13% had abnormal scars compared with none of those after the low-segment transverse operation (P = 0.0014). The frequency of scar dehiscence was 6% after a classical scar compared with none after a low-segment transverse scar (P = 0.0581).

Low vertical uterine incision in caesarean section

Eleven of the 3,420 Caesarean sections performed in Westmead Hospital, Sydney during a 6-year period from 1979 to 1985 were by a low vertical uterine incision. All the others were the standard transverse lower segment operation except for 1 which was a postmortem classical Caesarean section. There are indications when the preferred lower segment Caesarean section with a transverse incision should be avoided in the interest of the mother and baby. A low vertical incision has more advantages and less dangers than a classical fundal incision. It is prudent to defer the decision regarding the type of incision until the uterus is inspected intraoperatively. If access to the lower uterine segment is limited by prematurity, an obstructing lesion, a transverse lie, or if the presenting part is high and difficulty in delivering the baby is anticipated, a low vertical incision should be considered.