Thinner endometrial thickness linked to higher placenta accreta spectrum risk

Thinner endometrial thickness linked to higher placenta accreta spectrum risk | Image Credit: © Orawan - © Orawan - stock.adobe.com.

Endometrial thickness (EMT) is associated with the risk of placenta accreta spectrum (PAS) among women without previous cesarean delivery (CD) undergoing treatment using assisted reproductive technology (ART), according to a recent study published in the American Journal of Obstetrics & Gynecology.¹

PAS disorders have been linked to significant maternal morbidity and mortality, being the leading cause of hemorrhage, blood product transfusion, and emergency postpartum hysterectomy.² Risk factors of PAS include prior CD, placenta previa, in vitro fertilization (IVF), and maternal age of 35 years or older.¹

PAS is often asymptomatic, making early identification crucial. As the innermost layer of the uterus, the endometrium is vital for embryo development, with data indicating a significant impact of EMT on pregnancy outcomes. Therefore, there may be a link between EMT and PAS.

To evaluate the association between EMT and PAS incidence among woman without CD history conceiving through IVF or intracytoplasmic sperm injection, investigators conducted a retrospective study. Participants included patients receiving IVF or ICSI at the Third Affiliated Hospital of Guangzhou Medical University.

ART was provided between January 2, 2008, and July 1, 2020. Pertinent data was collected from the Reproductive Medicine Center and Obstetrics Database, with EMT measured by multiple experienced doctors on the day of trigger.

Ovarian stimulation was mainly conducted through artificial hormone replacement, the agonist protocol, and the antagonist protocol. PAS disease was the primary outcome of the analysis, defined as “a series of diseases with abnormal adhesion of trophoblastic tissue and invasion through the uterine serosa.”

PAS categories included placenta accreta, placenta increta, and placenta percreta. International Federation of Gynecology and Obstetrics guidelines were used to diagnose PAS in patients.

There were 4637 women included in the final analysis, 3.4% of whom had pregnancy complicated with PAS. Of these 159 PAS cases, 58 underwent vaginal delivery and 101 CD.

Increased gravidity, abortion history incidence, and rates of blastocyst-stage transfers were observed in patients with PAS. A significant decrease in EMT before embryo transfer was reported in PAS pregnancies vs non-PAS pregnancies.

Placenta previa, preeclampsia, and puerperal infection were more common in pregnancies impacted by PAS. However, other maternal and neonatal outcomes did not differ between groups.

The curve displaying the link between EMT and PAS showed an initial decline, followed by a plateau linked to increasing EMT. The transition occurred at an EMT of 10.9 mm.

A positive correlation was reported between thinning EMT and PAS, with an adjusted odds ratio (aOR) of 2.27 for EMT between 7 and 10.9 mm vs 7.15 for EMT under 7 mm. The risk of PAS was not increased among women with an EMT over 13 mm vs those with an EMT between 10.9 and 13 mm.

Of women with an EMT under 7 mm, placenta previa was reported in 1.81%. This rate was significantly higher than those identified in other groups.

Gravidity and the ovarian stimulation protocol were both independently linked with EMT, with a thinner EMT reported among patients with increased gravidity or a reduced duration of ovarian stimulation. However, the direct effects of gravidity and ovarian stimulation on PAS were 0.006 and 0.043, respectively.

These results indicated an association between a thinner EMT and increased PAS risk. Investigators concluded EMT should be considered a crucial factor when guiding future ART treatment.

Reference

1. Lai S, Zhang L, Luo Y, et al. A sonographic endometrial thickness <7 mm in women undergoing in vitro fertilization increases the risk of placenta accreta spectrum. Am J Obstet Gynecol. 2024;231:557.e1-18. doi:10.1016/j.ajog.2024.02.301
2. Upson K, Silver RM, Greene R, Lutomski J, Holt VL. Placenta accreta and maternal morbidity in the Republic of Ireland, 2005-2010. J Matern Fetal Neonatal Med. 2014;27(1):24-9. doi:10.3109/14767058.2013.799654