The impact of selective episiotomy on maternal short-term morbidity: a retrospective study

Figures & data

Figure 1. Flowchart of the study cohort.

Table 1. Demographic characteristics of the two exposure study cohorts as well as the distribution of the main two outcomes of severe perineal tears and blood loss with crude descriptive statistical analyses.

	Non-exposed (NoEPI) (n = 10821)	Exposed (EPI) (n = 171)	p value
Maternal age, years	31.9 ± 5.0	32.0 ± 4.6	0.84
Gestational age, median (Q1–Q3) (days)	279 (273–284)	280 (274–285)	0.30
Birth weight, grams	3410 ± 446	3391 ± 452	0.57
Maternal BMI (kg/m^2)	23.7 ± 4.8	22.2 ± 3.4	< 0.001
Nulliparity, n (%)	5315 (49.1)	136 (79.5)	< 0.001
Induction of labour, n (%)	1617 (14.9)	30 (17.5)	0.34
Duration of labour, median (Q1–Q3) (minutes)	270 (146–486)	364 (239–609)	< 0.001
Epidural analgesia, n (%)	4426 (40.9)	98 (57.3)	< 0.001
Mode of vaginal delivery			< 0.001
Spontaneous, n (%)	7880 (72.8)	71 (41.5)
Operative, n (%)	2941 (27.2)	100 (58.5)
Foetal presentation			< 0.001
Regular cephalic, n (%)	9605 (88.8)	135 (78.9)
Irregular cephalic, n (%)	320 (3.0)	9 (5.3)
Breech, n (%)	896 (8.3)	27 (15.8)
Severe perineal tears, n (%)	156 (1.4)	3 (1.8)	0.73
Blood loss, median (Q1–Q3) (ml)	250 (200–300)	300 (200–400)	< 0.001

Abbreviations: EPI: Episiotomy cohort, NoEPI: Non-exposed cohort, BMI: Body mass index.

Figure 2. Distribution of the propensity score density based on the exposure to an episiotomy.

Table 2. Multivariate logistic regression model to create the propensity scores predicting the probability of performing an episiotomy as a function of potential confounders (age, gestational age, birth weight, BMI, nulliparity, induction of labour, duration of labour, epidural analgesia, mode of vaginal delivery, foetal presentation).

Episiotomy as outcome	Coefficient (95% CI)	SD	p value
Intercept	–4.711 (–13.001, 3.581)	4.231	0.265
Maternal age in years	0.066 (0.017, 0.115)	0.025	0.008
Gestational age in days	–0.013 (–0.044, 0.017)	0.015	0.39
Birth weight in grams	9.001 (0.00005, 0.0012)	0.0003	0.033
Maternal BMI (kg/m^2)	–0.079 (–0.144, −0.014)	0.033	0.017
Nulliparity	1.698 (1.033, 2.363)	0.339	< 0.001
Induction of labour	0.376 (–0.172, 0.925)	0.279	0.179
Duration of labour in minutes	–0.0004 (–0.001, 0.0004)	0.0004	0.313
Epidural analgesia	–0.044 (–0.554, 0.465)	0.259	0.864
Mode of vaginal delivery (reference spontaneous)
Operative	1.436 (0.872, 2.001)	0.288	< 0.001
Foetal presentation (reference regular cephalic)
Irregular cephalic	–0.272 (–1.461, 0.917)	0.606	0.654
Breech	0.476 (–0.084, 1.036)	0.286	0.096

Abbreviations: CI: Confidence interval, SD: Standard error, BMI: Body mass index.

Table 3. Covariate balance and standardised differences between the episiotomy exposed (EPI) and the non-exposed (NoEPI) cohorts in the new dataset after the inverse probability weighting propensity score model.

Parameter	Standardised differences		Variance ratio
	Unweighted	Weighted	Unweighted	Weighted
Number of observations	5,382	5,382.0	–	–
Exposed (episiotomy)	89	2,605.1
Non-exposed (NoEPI)	5,293	2,776.9
Maternal age in years	0.144	0.041	0.613	0.366
Gestational age in days	0.043	0.008	1.289	1.175
Birth weight in grams	–0.004	0.083	1.119	0.971
Maternal BMI (kg/m^2)	–0.378	0.064	0.467	0.725
Nulliparity	0.822	0.134	0.505	0.981
Induction of labour	0.131	0.219	1.249	1.378
Duration of labour in minutes	0.293	0.194	0.943	0.698
Epidural analgesia	0.314	0.262	1.062	1.053
Mode of vaginal delivery (reference spontaneous)
Operative	0.983	0.144	0.877	1.093
Foetal presentation (reference regular cephalic)
Irregular cephalic	–0.007	0.023	0.976	1.119
Breech	0.429	–0.048	2.203	0.873

Abbreviations: BMI: Body mass index.

Data availability statement

Anonymised unidentifiable raw data from this project are available for at least 5 years after publication upon request.