Prediction of scar integrity and vaginal birth after caesarean delivery

Abstract

A statistically significant association with uterine rupture during a trial of labour after caesarean delivery was found in at least two studies for the following variables: interdelivery interval (higher risk with short interval), birthweight (higher risk if > 4000g), induction of labour (higher risk), oxytocin dose (higher risk with higher doses), and previous vaginal delivery (lower risk). However, no clinically useful risk estimation model including clinical variables has been published. A thin lower uterine segment at 35-40 weeks as measured by ultrasound in women with a caesarean hysterotomy scar increases the risk of uterine rupture or dehiscence. However, no cutoff for lower uterine segment thickness can be suggested because of study heterogeneity, and because prospective validation is lacking. Large caesarean hysterotomy scar defects in nonpregnant women seen at ultrasound examination increase the risk of uterine rupture or dehiscence in subsequent pregnancy but the strength of the association is unknown. To sum up, we currently lack a method that can provide a reliable estimate of the risk of uterine rupture or dehiscence during a trial of labour in women with caesarean hysterotomy scar(s).

Trial of Labor After Cesarean Section Among Women with Unique Lower Segment Scarred Uterus and Fetal Weight >3500 g: Prognostic Factors for a Safe Vaginal Delivery

“…Women who had vaginal delivery prior to (or after) the first CS had better chances (94.1 %) of successful TOLAC in our series, as noticed in Sweden and India, respectively [5,15]. This explains why women of parity C2 had better outcome of TOLAC than women of parity 1 in our series (P = 0.006).…”

“…This difference is probably due to our small sample or to the high BW in our series. This shows that TOLAC with an estimated fetal weight[4000 g is risky, as observed in Sweden [5], and all preparations should be made for rapid CS if signs of imminent uterine rupture are present.…”

“…Because of this rising CS rate, some women in subsequent deliveries have to go through a trial of labor after cesarean section (TOLAC) (observation, under normal uterine contractions, of labor outcome in women with a lower segment scarred uterus and who fulfill certain criteria). For many authors, to be eligible for a TOLAC with a reduced risk of uterine rupture or dehiscence, women should fulfill some criteria such as a unique lower uterine segment transverse scar, a time interval between CS and next conception of C12 months, a vertex presentation, a radiologically adequate pelvis, a fetus weighing \3500 g and the absence of other medical or obstetrical complications [5,6].…”

Morphology of the cesarean section scar in the non-pregnant uterus after one elective cesarean section

“…Many of these women will pursue future pregnancies, and they are at risk of potentially life treating complications of primary CS [5]. These complications include cesarean scar pregnancy, morbidly adherent placenta, and CS scar dehiscence and rupture [2,[5][6][7][8]. A growing number of studies suggest that the occurrence of long-term consequences of CS is related to the incomplete healing of the CS scar in the uterus, i.e., the development of a niche within the scar [7][8][9][10].…”

“…These complications include cesarean scar pregnancy, morbidly adherent placenta, and CS scar dehiscence and rupture [2,[5][6][7][8]. A growing number of studies suggest that the occurrence of long-term consequences of CS is related to the incomplete healing of the CS scar in the uterus, i.e., the development of a niche within the scar [7][8][9][10]. According to these studies, ultrasonographic assessment of the morphology of the CS scar in women who are not currently pregnant may predict the occurrence of CS scar dehiscence and rupture during subsequent pregnancies.…”