P-393 Operative hysteroscopy versus vacuum aspiration for missed miscarriage in women undergoing in vitro fertilization, a propensity score-matched cohort study
Authors: Hu K  L , Li R 
Published: July 2024

Abstract

Study question
Is operative hysteroscopy, compared to vacuum aspiration, associated with increased success rates in the subsequent frozen embryo transfer of women who experienced missed miscarriage?

Summary answer
Operative hysteroscopy does not show advantages in terms of live birth rate in the subsequent frozen embryo transfer compared to women who underwent vacuum aspiration.

What is known already
As hysteroscopy to remove retained product of conception is performed under direct visualization control, it may theoretically reduce risks to the uterine cavity and therefore improve future fertility. With the advancements in hysteroscopy technology, an increasing number of women with missed miscarriage are choosing operative hysteroscopy over conventional vacuum aspiration. However, there is currently insufficient research available to determine whether use of operative hysteroscopy to remove retained tissues within the uterus effectively increases the success rate of subsequent frozen embryo transfer.

Study design, size, duration
This was a propensity score-matched cohort study on women who had experienced an missed miscarriage at 5 to 16 gestational weeks during an IVF cycle in Peking University Third Hospital from 2015 to 2022.

Participants/materials, setting, methods
We aimed to focus on a specific group of patients who had experienced missed miscarriage during IVF and subsequently underwent frozen embryo transfer. Logistic regression models were used to compare the effect of operative hysteroscopy versus vacuum aspiration, after propensity score matching with a 1:1 ratio. Non-linear interaction was tested on gestational weeks and treatment effect on live birth rate. The primary outcome was the live birth rate in the subsequent frozen embryo transfer.

Main results and the role of chance
Out of the 3,722 fresh embryo transfer cycles and 5,948 frozen embryo transfer cycles resulting in miscarriage, a total of 2,562 women who underwent vacuum aspiration and 347 women who underwent operative hysteroscopy were included in the analysis. After propensity score matching at a 1:1 ratio, 324 women were included in each group. Compared to women who underwent vacuum aspiration, those who underwent operative hysteroscopy were associated with a lower rate of live birth in the propensity-based matched cohort (29% vs 22%, aOR = 0.67 (0.47, 0.96)). The result was further confirmed by several sensitivity analysis, including using non-imputed data, varying calliper widths for propensity score matching, and matching covariates associated with treatment assignment or pregnancy outcomes. No statistical difference was detected on the biochemical pregnancy rate, clinical pregnancy rate, multiple pregnancy rate, and miscarriage rate. No interaction was detected between the gestational week and the relative treatment effect on live birth (p = 0.75). There was no significant difference in the rate of neonatal outcomes between the vacuum aspiration and operative hysteroscopy groups. 11 women experienced surgery reintervention in the vacuum aspiration group (0.4%), while no one required surgery reintervention in the operative hysteroscopy group.

Limitations, reasons for caution
The retrospective design and inability to analyze certain confounding factors are notable limitations, despite achieving covariate balance through matching. Our dataset did not capture several important outcomes, including cumulative pregnancies and severe complications after surgery. Future randomised trials are warranted to provide more robust insights into our results.

Wider implications of the findings
Women may benefit from operative hysteroscopy with a lower rate of reintervention compared to vacuum aspiration. However, this advantage may come at the expense of lower rates of live birth. Our results should be further tested by randomised trials.

Trial registration number
NA