Instrument selection in assisted vaginal delivery, when spontaneous vaginal delivery is no longer an option

We thank Iqbal et al.¹ for their interest in our paper² and for raising important concerns about our methodology and interpretation.

Not accounting for preexisting the fear of childbirth (FOC) in our analysis is problematized by the authors. It is correct that this is associated with secondary FOC and has not been measured in our study.³ Including preexisting FOC could introduce selection bias, as women with more severe FOC could more likely opt for elective Cesarean delivery (CD), underestimating its effect on the birth experience following vaginal delivery. However, we believe that the choice of instrument is unlikely to be influenced by primary FOC, making it improbable that primary FOC would affect one assisted vaginal delivery (AVD) cohort more than the other.

Using spontaneous vaginal delivery (SVD) as a reference to AVD has its limitations as they are not perfectly comparable. SVD is not an option for AVD, but instruments are largely interchangeable. Despite this, it is reassuring that the AVD cohorts do not significantly differ from SVD, especially since the real alternative, emergency CD, is the mode of delivery most strongly associated with a negative birth experience.⁴

Large differences in FOC prevalence are seen around the world from 3.7% to 43%,⁵ with around 8% reported in Norway, where our study was conducted. Our primary aim was to compare the two instruments. The comparison to SVD may have been underpowered although it is questionable whether any difference between AVD and SVD would be clinically significant at this low baseline prevalence.

There is no gold standard for the adequate time for measuring the birth experience. As we discuss in our paper, there are risks of both overestimating and underestimating the outcome in different time periods. A trend of improvement over time is generally seen, although the changes are not dramatic.³ It seems rather unlikely that one AVD cohort would behave differently from the other in such regard. We wanted to assess intrapartum factors associated with secondary FOC. We acknowledge that these feelings might develop later, as well as that intrapartum factors might lead to long-term complications for example, after pelvic trauma. We did sub-analyses of FOC in women after SVD with and without episiotomy. No difference was found, although the numbers were small. Whether any long-term problems related to pelvic trauma could lead to a FOC before a subsequent pregnancy is unknown but could be a subject for a follow-up study of our cohort.

We agree that more research is needed to identify factors that could reduce FOC. If there are differences between the instruments, they were too small to be detected in our study, and therefore we question their clinical relevance. Any operative intervention in childbirth should of course be limited to those cases where the benefit is assumed greater than the risk. Keeping this in mind, it is important to recognize that when an AVD is indicated, a spontaneous vaginal birth is no longer an option.