(922) Association of ultrasound determined hysterotomy thickness and intraoperative scar thinning/dehiscence after fetal spina bifida closure

To study the association between ultrasound determined myometrial thickness and intraoperative findings of scar thinning or dehiscence at the time of cesarean delivery in patients undergoing open maternal fetal surgery (OMFS) for fetal spina bifida (fSB) closure.


Study Design:

A retrospective review of all cases of OMFS for fSB closure from 2016-2022. Hysterotomy scar thickness was measured on archived images at 30 weeks, 32 weeks, 34 weeks and 36 weeks. Three measurements of myometrial thickness were taken for every timepoint in sagittal plane. The group with intact hysterotomy was compared to those with scar thinning/ dehiscence.


Results:

111 patients met the inclusion criteria. The average hysterotomy scar thickness was 0.83 ± 0.18 cm, 0.78 ±0.19 cm, 0.72 ± 0.18 cm and 0.71 ± 0.22 cm at 30, 32, 34 and 36 weeks, respectively. 54.1% patients had at least some degree of scar thinning and 6.3% patients had some degree of dehiscence including focal. Scar thickness was significantly lower at 34 weeks (p=0.02) and 36 weeks (p< 0.0001) in patients that had thinning/dehiscence. δ scar thickness between 30 and 36 weeks was significantly more in patients with scar thinning/dehiscence (p=0.0009). AUC was 0.63 with a p-value of 0.02 for hysterotomy thickness at 34 weeks predicting absence of thinning. AUC was 0.82 with a p-value of < 0.0001 for hysterotomy thickness at 36 weeks predicting absence of thinning. A thickness of ≥ 0.71 cm was 68.6% sensitive and 84.9% specific in predicting absence of thinning. AUC was 0.76 with a p-value of 0.0003 for ð hysterotomy thickness between 30-36 weeks predicting presence of thinning/dehiscence. A change of ≥ 0.13 cm was 69.7% sensitive and 73.5% specific in predicting presence of thinning/dehiscence.

 

Conclusion:

In patients undergoing OMFS for fSB repair, gradual thinning of hysterotomy scar was observed with significantly less scar thickness at 34 and 36 weeks in patients diagnosed with scar thinning/ dehiscence. δ scar thickness between 30 and 36 weeks can be used to predict presence of thinning/dehiscence.