Background
The term cesarean scar pregnancy refers to placental implantation within the scar of a previous cesarean delivery.
The rising numbers of cesarean deliveries in the last decades have led to an increased
incidence of cesarean scar pregnancy. Complications of cesarean scar pregnancy include
morbidly adherent placenta, uterine rupture, severe hemorrhage, and preterm labor.
It is suspected that cesarean scar pregnancies that are implanted within a dehiscent
scar (“niche”) behave differently compared with those implanted on top of a well-healed
scar. To date there are no studies that have compared pregnancy outcomes between cesarean
scar pregnancies implanted either “on the scar” or “in the niche.”
Objectives
The purpose of this study was to determine the pregnancy outcome of cesarean scar
pregnancy implanted either “on the scar” or “in the niche.”
Study Design
This was a retrospective 2-center study of 17 patients with cesarean scar pregnancy
that was diagnosed from 5–9 weeks gestation (median, 8 weeks). All cesarean scar pregnancies
were categorized as either implanted or “on the scar” (group A) or “in the niche”
(group B), based on their first-trimester transvaginal ultrasound examination. Clinical
outcomes based on gestational age at delivery, mode of delivery, blood loss at delivery,
neonate weight and placental histopathologic condition were compared between the groups
with the use of the Mann-Whitney U test. Myometrial thickness overlying the placenta was compared among all the patients
who required hysterectomy and those who did not with the use of the Mann-Whitney U test. Myometrial thickness was also correlated with gestational age at delivery with
the use of Spearman’s correlation.
Results
Group A consisted of 6 patients; group B consisted of 11 patients. Gestational age
at delivery was lower in group B (median, 34 weeks; range, 20–36 weeks) than in group
A (median, 38 weeks; range, 37–39 weeks; P=.001). In group A, 5 patients were delivered via cesarean delivery (with normal placenta),
and 1 patient underwent a cesarean-hysterectomy for placenta accreta. In group B,
10 patients had a cesarean-hysterectomy for placenta increta/percreta, and 1 patient
underwent gravid-hysterectomy for vaginal bleeding at 20 weeks gestation. Blood loss
was increased, but not significantly higher in group B (median, 1200 mL; range, 600–4000
mL) than in group A (median, 700 mL; range, 600–1400 mL; P=.117). Myometrium was statistically significantly thinner in the patients group that
require hysterectomy (median, 1 mm; range, 0–2 mm) than in the group that did not
(median, 5 mm; range, 4–9 mm; P=.001). Myometrial thickness showed a positive correlation with the gestational age
(r=0.820; P<.0005).
Conclusion
Patients with cesarean scar pregnancy implanted “on the scar” had a substantially
better outcome compared with patients in whom the cesarean scar pregnancy implanted
“in the niche.” Myometrial thickness <2 mm in the first-trimester ultrasound examination
is associated with morbidly adherent placenta at delivery.
Key words
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Article Info
Publication History
Published online: January 20, 2017
Accepted:
January 13,
2017
Received in revised form:
December 20,
2016
Received:
November 14,
2016
Footnotes
The authors report no conflict of interest.
Cite this article as: Kaelin Agten A, Cali G, Monteagudo A, et al. The clinical outcome of cesarean scar pregnancies implanted “on the scar” versus “in the niche.” Am J Obstet Gynecol 2017;216:510.e1-6.
Identification
Copyright
© 2017 Elsevier Inc. All rights reserved.
