Yesterday I shared a Canadian article, and last year a letter from two OBs opposing a hospital VBAC ban, which discuss the risks of cesarean sections including placenta accreta and hysterectomy.

Today I want to share a study, but before I do so, lets do a quick review of definitions.

Placenta accreta (Wikipedia):

Placenta accreta is a severe obstetric complication involving an abnormally deep attachment of the placenta, through the endometrium and into the myometrium (the middle layer of the uterine wall). There are three forms of placenta accreta, distinguishable by the depth of penetration.

The placenta usually detaches from the uterine wall relatively easily, but women who encounter placenta accreta during childbirth are at great risk of haemorrhage during its removal. This commonly requires surgery to stem the bleeding and fully remove the placenta, and in severe forms can often lead to a hysterectomy or be fatal.

Placenta accreta affects approximately 1 in 2,500 pregnancies.

Hysterectomy (Wikipedia):

A hysterectomy (from Greek ὑστέρα hystera "womb" and εκτομία ektomia "a cutting out of") is the surgical removal of the uterus, usually performed by a gynecologist. Hysterectomy may be total (removing the body, fundus, and cervix of the uterus; often called "complete") or partial (removal of the uterine body but leaving the cervical stump, also called "supracervical"). It is the most commonly performed gynecological surgical procedure. In 2003, over 600,000 hysterectomies were performed in the United States alone, of which over 90% were performed for benign conditions.^[1] Such rates being highest in the industrialized world has led to the major controversy that hysterectomies are being largely performed for unwarranted and unnecessary reasons. ^[2]

Removal of the uterus renders the patient unable to bear children (as does removal of ovaries and fallopian tubes), and changes her hormonal levels considerably, so the surgery is normally recommended for only a few specific circumstances:

Placenta previa (Wikipedia):

Placenta praevia (placenta previa AE) is an obstetric complication in which the placenta is attached to the uterine wall close to or covering the cervix [2]. It can sometimes occur in the later part of the first trimester, but usually during the second or third. It is a leading cause of antepartum haemorrhage (vaginal bleeding).

Today’s study is Maternal morbidity associated with multiple repeat cesarean deliveries (Silver 2006) which is a good sized study focusing on the risks of repeat cesareans and how those risks increase as the number of prior surgeries increase.  This statement sums up their findings:

The risks of placenta accreta, cystotomy [surgical incision of the urinary bladder], bowel injury, ureteral [ureters are muscular ducts that propel urine from the kidneys to the urinary bladder] injury, and ileus [disruption of the normal propulsive gastrointestinal motor activity], the need for postoperative ventilation, intensive care unit admission, hysterectomy, and blood transfusion requiring 4 or more units, and the duration of operative time and hospital stay significantly increased with increasing number of cesarean deliveries.

Since I’m a visual person, I wanted to chart their findings because I think it makes the information easier to digest.

Remember as you look these over, the risk of uterine rupture in a spontaneous labor after one prior low horizontal (“bikini-cut”) cesarean is 0.4% (Landon 2004), which is lower than your risk of hysterectomy after one prior cesarean (0.65%) and your risk of accreta after three cesareans (0.57%).  Risk of uterine rupture after two cesareans is 0.9%. (Landon 2006)

Risk of Placenta Accreta & Hysterectomy by Number of Prior Cesareans

Risk of Placenta Accreta when Placenta Previa is Present by Number of Prior Cesareans

Here is the study abstract:

Obstet Gynecol. 2006 Jun;107(6):1226-32.

Maternal morbidity associated with multiple repeat cesarean deliveries.

Silver RM, Landon MB, Rouse DJ, Leveno KJ, Spong CY, Thom EA, Moawad AH, Caritis SN, Harper M, Wapner RJ, Sorokin Y, Miodovnik M, Carpenter M, Peaceman AM, O’Sullivan MJ, Sibai B, Langer O, Thorp JM, Ramin SM, Mercer BM; National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network.

Department of Obstetrics and Gynecology, University of Utah School of Medicine, Salt Lake City, Utah 84132, USA. Bob.Silver@hsc.utah.edu

OBJECTIVE: Although repeat cesarean deliveries often are associated with serious morbidity, they account for only a portion of abdominal deliveries and are overlooked when evaluating morbidity. Our objective was to estimate the magnitude of increased maternal morbidity associated with increasing number of cesarean deliveries. METHODS: Prospective observational cohort of 30,132 women who had cesarean delivery without labor in 19 academic centers over 4 years (1999-2002). RESULTS: There were 6,201 first (primary), 15,808 second, 6,324 third, 1,452 fourth, 258 fifth, and 89 sixth or more cesarean deliveries. The risks of placenta accreta, cystotomy, bowel injury, ureteral injury, and ileus, the need for postoperative ventilation, intensive care unit admission, hysterectomy, and blood transfusion requiring 4 or more units, and the duration of operative time and hospital stay significantly increased with increasing number of cesarean deliveries. Placenta accreta was present in 15 (0.24%), 49 (0.31%), 36 (0.57%), 31 (2.13%), 6 (2.33%), and 6 (6.74%) women undergoing their first, second, third, fourth, fifth, and sixth or more cesarean deliveries, respectively. Hysterectomy was required in 40 (0.65%) first, 67 (0.42%) second, 57 (0.90%) third, 35 (2.41%) fourth, 9 (3.49%) fifth, and 8 (8.99%) sixth or more cesarean deliveries. In the 723 women with previa, the risk for placenta accreta was 3%, 11%, 40%, 61%, and 67% for first, second, third, fourth, and fifth or more repeat cesarean deliveries, respectively. CONCLUSION: Because serious maternal morbidity increases progressively with increasing number of cesarean deliveries, the number of intended pregnancies should be considered during counseling regarding elective repeat cesarean operation versus a trial of labor and when debating the merits of elective primary cesarean delivery. LEVEL OF EVIDENCE: II-2.