Thickness of the lower uterine segment: its influence in the management of patients with previous cesarean sections

Prediction of scar integrity and vaginal birth after caesarean delivery

“…The review comprises 12 studies published between 1988 and 2009 [12,[33][34][35][36][37][38][39][40][41][42][43] including together 1834 women with a previous low transverse caesarean hysterotomy who underwent ultrasound measurement of the thickness of the lower uterine segment at [35][36][37][38][39][40] gestational weeks. In seven of the 12 studies the full lower uterine segment thickness was measured [12,33,36,[38][39][40]42], in four studies the myometrial thickness was measured [34,35,37,43], and in one study both measurements were taken [41].…”

“…In seven of the 12 studies the full lower uterine segment thickness was measured [12,33,36,[38][39][40]42], in four studies the myometrial thickness was measured [34,35,37,43], and in one study both measurements were taken [41]. Because only three of the 12 studies reported the frequency of uterine rupture separately, the outcome measure was "uterine rupture or uterine dehiscence", i.e.…”

“…The cutoffs suggested for the full lower uterine segment thickness in the different studies varied between 2.0 mm and 3.5 mm and those for the myometrial thickness between 1.4 mm and 2.0 mm. It is of note that in nine of the 12 studies included in the review the ultrasound results were available to the staff managing the pregnancies and deliveries [33][34][35][38][39][40][41][42][43]. This is inappropriate when estimating sensitivity and specificity of a diagnostic test.…”

“…Rozenberg et al [42] introduced measurement of the lower uterine segment with the 3.5 mm cutoff into clinical practice after their observational study [12] had been closed. They compared the results for 1995 -1996 after the method had been implemented clinically with those in their observational study (1989)(1990)(1991)(1992)(1993)(1994)) with regard to the frequency of uterine dehiscence or rupture, the frequency of planned and emergency caesarean delivery, and the use of oxytocin in women with previous caesarean delivery.…”

“…In studies reporting on measurements of the thickness of the lower uterine segment the measurement technique was described with varying detail [12,[33][34][35][36][37][38][39][40][41][42][43]. Therefore, it is unlikely that exactly the same transabdominal measurement technique or exactly the same transvaginal measurement technique was used in all studies: there may be differences between the degree of bladder filling, the site of measurement, the placement of the callipers, the number of measurements taken and in the measurement selected to be representative if more than one was taken.…”