Placenta accreta spectrum (PAS) is growing worldwide,1 reaching epidemic proportions in many countries. There is not a simple and global solution to reduce the incidence of cesarean, because it is affecting by multifactorial problems.2 Although new, complete, and updated guides3–6 tried to cover all aspects in relation with the PAS, none of them has proposed a practical solution to stop this frightening disease.
Even in countries with a two babies’ policy, like China, increasing the frequency of PAS 7–9 reaching to alarming proportions, especially in their serious form. At this moment, it is obvious that cesarean rates reduction is not a goal to decrease PAS, and it is probably that related maternal mortality and morbidity may grow at unsuspected levels in a short time.10
When we put our attention to the origin of the PAS, there is always a common factor: the uterine damage.11,12 It is known, that the most common cause of uterine damage is the cesarean, that heal by fibrosis and results in a non-elastic tissue. When traction forces are applied over an inextensible scar, habitually it is cause of an additional damage, myometrial thinning, uterine defects, and collagen exposure; all of them, associated with the etiology of PAS.13 This fact could explain why PAS is more frequently in patients with multiple cesarean or other causes of uterine damage, such as cesarean scar pregnancy, abortions, and dilation and curettage (D&C). But, this theory does not explain why PAS is also appearing after the first cesarean. In these cases, an alternative mechanism could produce a primary uterine defect. Dr. Vikareva Osser was the first investigator that associated large cesarean defects in patient with long labor or when the cesarean was performed in the second stage.14 Finding that was reconfirmed later (2018) in a large double-blind trial by the same author. In these circumstances, the uterine segment is unfolded by intense collagenase action, which results in an anatomic modification of the uterine segment and its relative position respect to the cervical os. In those cases, it is frequently that cesarean is performed as lower than obstetricians believed (even to a few cm of the cervix).
In some cases, and apparently for some unknown reasons, subsequent healing is compromised and hysterotomy may result in a spontaneous dehiscence and a subsequent development of a lower uterine full-thickness defect. Anatomically, when a low-transverse incision is done, blood supply by cervical-vaginal artery is compromised leaving a hypovascularized area. The continuity of vessels and blood supply is disturbed especially if some uterine vessels are transected during the incision extension.15 Healing in the lower uterine segment will need excess blood supply as it is already diminished after the transverse lower incision.
By coincidence, in some countries with an elevated rate of PAS after first cesarean, also had a high cesarean rate after a long labor or when it is performed in the second stage of labor. Histologically, the uterine segment is part of the cervix and also have a high collagen percentage, which is higher, when is closer to the uterine cervix. Spontaneous defects after cesarean in lower uterus are habitually large and difficult to heal. Strikingly, primary repair of lower uterine full-thickness defects has an inexplicable an elevated rate of spontaneous recurrence, fact that do not happen in upper uterus repair, even when an identical surgical technique is using. Immunocytochemical analysis of the defect's borders – in cases of spontaneous dehiscence – showed a complete absence of growth factors (personal unpublished data), element that would explain the unprompted dehiscence and the elevated rate of recurrence after primary surgical repair. In both cases, recurrent cesarean with scar damage and lower full thickness uterine defects would explain the etiology of PAS in both groups.
Decidua does not develop below the uterine incision, because uterine segment is thin, with poor blood supply, as consequence, only amnion layer is seen15 This fact, in addition with a poor or incomplete decidualization in the uterine segment16 can complete this unwanted combination Although there are a few controversies about the exact place to do the cesarean access, the elevated percentage of uterine collagen in the uterine segment allows less bleeding and easy closure, but, it could involve more unnoticed complications in the future. John Martin Munro-Kerr17 mentioned about possible of uterine damage in multiple cesarean. He said that although uterine segment is ideal to perform a cesarean (reduced bleeding and thin uterine wall) the high percentage of elastic and collagen tissue could be the cause of healing problems.
A superior border of the uterine segment corresponding to the point of close adherence of peritoneum to the uterine wall, area with a remarkable thickness change in the uterine wall. The inferior limit, before labor, it is the internal os. Three zones can be identified: a short superior, an intermediate zone; an inferior, which is the thinnest: height 2–4 cm, behind the bladder, loose at the beginning and its adherent become firm.18 Use a high incision at lower segment (short superior) could change this problem in a very simple way. Although there are no much descriptions to identify this area, a prospective work19 has demonstrated that hysterotomy performed at this level, it is safe and easy to repair. At that level, the blood supply is provided by direct and anastomosed branches of both uterine arteries,20 fact that guarantee an optimal healing and appropriate release of growth factors. While many obstetricians believe that to perform an upper hysterotomy implies more risk for subsequent uterine rupture, there are no formal papers that support this affirmation, nevertheless, there one recent review that dismisses this risk.19
Perhaps, repair of full-thickness defects eliminates the preexistent factor for PAS and to perform an upper hysterotomy eradicate healing problems and the existence of large full-thickness defects, which are also associated with PAS. It is possible, that was happened with the episiotomy,21 many years ago, that we need to rethink in older recommendations and to learn about the new insights about uterine healing to definitively cut off the cesarean-PAS high-risk morbid association.
Conflicts of Interest
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