Figure 1 presents the inclusion of the study sample. A total of 1049 women were included in the POPRACT study. Of the study population remaining after exclusion, 809 women had a vaginal delivery. Delivery was documented in the dedicated study protocol for 644 of these women, who thus constituted the present study sample. For the analysis of risk factors in relation to perineal and vaginal tears included 489 and 426 women, respectively, after excluding women with missing data in relevant variables.
Insert Fig. 1 approximately here.
Baseline and obstetric and baseline characteristics of the study sample are shown in Table 1 and Table 2, respectively. The sample had a mean (± SD) age of 28.7 ± 3.7 years (range: 18–41 years), BMI of 24.5 ± 4.4 kg/m2 (16.4–44.0 kg/m2), gestational age at birth of 40 weeks + 1 day ± 1 week + 3 days (34 weeks + 1 day – 42 weeks + 5 days), fetal birth weight of 3513 ± 472 g (1730–5140 g), and fetal head circumference of 34.8 ± 1.5 cm (28.0–38.5 cm). Smoking, symptoms of pelvic organ prolapse during late pregnancy, and lack of manual perineal protection were considered as potential risk factors but were excluded from the analysis of risk factors presented below due to too few exposed women. No statistically significant differences were found between the women whose data were collected according to study-specific delivery protocol registered (n = 644) and those excluded due to missing study protocol (n = 165), except regarding use of epidural analgesia and duration of active second stage of labor. In the excluded group, epidural use was lower (38.2%) and the mean duration of active second stage of labor was longer (48.7 ± 35.4 min; range: 1–189 min).
Table 1
Baseline characteristics of the study population.
| n (%) |
Age | |
≤25 years | 114 (17.7) |
26–30 years | 346 (53.8) |
31–35 years | 155 (24.1) |
>35 years | 28 (4.4) |
Missing | 0 |
BMI | |
≤25 kg/m2 | 405 (64.5) |
25.1–30 kg/m2 | 155 (24.7) |
>30 kg/m2 | 68 (10.8) |
Missing | 16 |
Smoking | |
Yes | 19 (3.0) |
No | 605 (97.0) |
Missing | 20 |
Education | |
9–<12 years | 8 (1.5) |
12 years | 181 (33.2) |
University | 357 (65.4) |
Missing | 98 |
Hereditya | |
Yes | 70 (14.4) |
No | 415 (85.6) |
Missing | 159 |
SUI during late pregnancy | |
Yes | 116 (22.2) |
No | 406 (77.8) |
Missing | 122 |
Symptoms of POP during late pregnancy | |
Yes | 22 (4.2) |
No | 501 (95.8) |
Missing | 121 |
Baseline characteristics of the study population. aHeredity of pelvic floor dysfunction and/or connective tissue deficiency. BMI, body mass index; POP, pelvic organ prolapse; SUI, stress urinary incontinence. |
Table 2
Obstetric characteristics of the study population.
| n (%) |
Gestational age at birth | |
Preterm (< 37w) | 21 (3.3) |
Term (37–42w) | 552 (85.7) |
Postterm (> 42w) | 60 (9.3) |
Missing | 11 |
Delivery start | |
Spontaneous | 512 (79.6) |
Induction | 131 (20.4) |
Missing | 1 |
Epidural analgesia | |
No | 314 (48.8) |
Yes | 330 (51.2) |
Missing | 0 |
Oxytocin stimulation | |
No | 306 (48.5) |
Yes | 325 (51.5) |
Missing | 12 |
Duration of active 2nd stage | |
≤15 min | 124 (19.9) |
16–60 min | 346 (55.5) |
>60 min | 154 (24.7) |
Missing | 20 |
Perineotomy | |
No | 579 (91.3) |
Yes | 55 (8.7) |
Missing | 9 |
Maternal position at birth | |
Position other than lithotomy | 282 (44.4) |
Lithotomy | 353 (55.6) |
Missing | 9 |
Mode of delivery | |
Spontaneous | 527 (81.8) |
Instrumental | 117 (18.2) |
Missing | 0 |
Manual perineal protection | |
None | 8 (1.3) |
Fetal head support only | 30 (4.8) |
Perineal head support only | 82 (13.0) |
Combined support | 409 (65.0) |
Unspecified support | 100 (15.9) |
Missing | 15 |
Fetal scalp electrode | |
No | 279 (44.2) |
Yes | 352 (55.8) |
Missing | 12 |
Fetal presentation | |
Occiput anterior | 611 (96.4) |
Occiput posterior | 23 (3.6) |
Breech | 0 |
Missing | 10 |
Fetal birth weight | |
≤4000 g | 541 (84.1) |
>4000 g | 102 (15.9) |
Missing | 1 |
Fetal head circumference | |
≤35 cm | 278 (43.4) |
>35 cm | 363 (56.6) |
Missing | 3 |
Number of births | |
Singleton | 641 (99.7) |
Twins | 2 (0.3) |
Missing | 1 |
Obstetric characteristics of the study population. Women where information is missing are not included in the percentage. |
Incidence of perineal, vaginal, and other vulvar tears
Table 3 presents the incidence of vaginal, perineal, and other vulvar tears. Almost half of the women (47.6%) contracted any labial tear requiring suturing. Anterior tears close to the clitoris or urethra were less common than labial tears, affecting 15.3% of the sample. Only 14.9% of women avoided any vaginal tear. The vast majority (71.1%) of women with vaginal tear had a low tear, whereas 14.0% contracted a high vaginal tear. About one third (31.1%) of women had an intact perineum, while the remaining two thirds had some degree of perineal tear. Second-degree tears constituted the majority of tears (44.7%). The incidences of third-degree tears of class A, B, and C were 3.7%, 1.1%, and 2.2% respectively. Only two women (0.32%) contracted a fourth-degree perineal tear.
Table 3
Distribution of vaginal, perineal, and other vulvar tear.
Labial tearsa | Total n = 628 n (%) |
None | 329 (52.4) |
Yes | 299 (47.6) |
Missing | 16 |
Anterior tearsb | Total n = 603 n (%) |
None | 511 (84.7) |
Yes | 92 (15.3) |
Missing | 41 |
Vaginal tear | Total n = 609 n (%) |
None | 91 (14.9) |
Lowc | 433 (71.1) |
Highd | 85 (14.0) |
Missing | 35 |
Degree of perineal tear | Total n = 626 n (%) |
None | 195 (31.1) |
First-degree | 106 (16.9) |
Second-degree | 280 (44.7) |
Third-degree (A) | 23 (3.7) |
Third-degree (B) | 7 (1.1) |
Third-degree (C) | 14 (2.2) |
Fourth-degree | 2 (0.32) |
Missing | 17 |
Distribution of vaginal, perineal, and other vulvar tear. An individual woman may have labial, anterior, vaginal and perineal tear concomitantly and thus be part of several tear groups. Missing information is due to incomplete information in the delivery protocols. alabial tears requiring suturing; banterior tears close to clitoris or urethra, not related to female genital mutilation; cvaginal tear where only the distal third of vagina is engaged; dvaginal tear more extensive than the distal third of vagina
Odds ratios for the risk factors of second-degree perineal tear and OASI
Table 4 presents the unadjusted and adjusted odds ratios for second-degree perineal tear and for OASI, respectively. Women with second-degree perineal tear were more likely to be older than 25 years, to have a post-term delivery, to be exposed to oxytocin augmentation, to give birth in the lithotomy position, to have delivery assisted by vacuum extraction, and to have a child heavier than 4000 g or with a head circumference exceeding 35 cm, compared to women who did not have tear or had a tear of first degree (the reference). After adjustment, age above 25 years, vacuum extraction, and fetal weight exceeding 4000 g remained as risk factors significantly increasing the risk of second-degree perineal tear. Women with OASI were more likely to use epidural analgesia, to be exposed to oxytocin augmentation, to have delivery assisted by vacuum extraction, to have a fetal heart beat monitored by scalp electrode, and to have a child heavier than 4000 g or with a head circumference exceeding 35 cm, compared to the reference. After adjustment, vacuum extraction and fetal weight > 4000 g remained as risk factors significantly increasing the risk of OASI.
Table 4
Unadjusted and adjusted odds ratios for risk factors for perineal tear
n = 489 | 2nd degree | OASI |
| OR (95% CI) | aOR (95% CI) | OR (95% CI) | aOR (95% CI) |
Age |
≤25 years | Reference | Reference | Reference | Reference |
>25 years | 2.01 (1.21, 3.35)* | 1.94 (1.10, 3.43)* | 1.56 (0.57, 4.25) | 1.70 (0.52, 5.59) |
BMI |
≤25 kg/m2 | Reference | Reference | Reference | Reference |
25.1–30 kg/m2 | 0.91 (0.58, 1.42) | 0.99 (0.61, 1.60) | 1.09 (0.47, 2.51) | 0.98 (0.39, 2.49) |
>30 kg/m2 | 1.22 (0.68, 2.19) | 1.08 (0.57, 2.05) | 0.55 (0.12, 2.50) | 0.26 (0.05, 1.40) |
Education | | | | |
9to < 12 years | 0.24 (0.03, 2.20) | 0.35 (0.04, 3.38) | 3.22 (0.56, 18.58) | 4.55 (0.60, 34.33) |
12 years | 0.82 (0.55, 1.21) | 0.92 (0.60, 1.42) | 0.63 (0.27, 1.47) | 0.61 (0.24, 1.60) |
University | Reference | Reference | Reference | Reference |
Hereditya |
No | Reference | NE | Reference | NE |
Yes | 1.33 (0.76, 2.32) | NE | 1.52 (0.53, 4.35) | NE |
SUI in late pregnancy |
No | Reference | NE | Reference | NE |
Yes | 0.66 (0.41, 1.05) | NE | 1.65 (0.74, 3.66) | NE |
GA at birth |
Preterm/term | Reference | Reference | Reference | Reference |
Postterm | 2.11 (1.09, 4.06)* | 1.73 (0.77, 3.86) | 2.01 (0.63, 6.48) | 1.22 (0.28, 5.26) |
Delivery start |
Spontaneous | Reference | Reference | Reference | Reference |
Induction | 1.38 (0.86, 2.21) | 0.96 (0.54, 1.74) | 1.6 (0.67, 3.81) | 1.33 (0.45, 3.91) |
Epidural analgesia |
No | Reference | Reference | Reference | Reference |
Yes | 1.76 (1.21, 2.55)* | 1.19 (0.75, 1.88) | 2.06 (0.98, 4.34)* | 0.84 (0.33, 2.11) |
Oxytocin stimulation |
No | Reference | Reference | Reference | Reference |
Yes | 1.76 (1.21, 2.55)* | 1.19 (0.75, 1.88) | 2.06 (0.98, 4.34)* | 0.84 (0.33, 2.11) |
Duration of active 2nd stage |
≤15 min | 0.74 (0.45, 1.23) | 0.79 (0.47, 1.35) | 1.2 (0.49, 2.92) | 1.52 (0.57, 4.03) |
16–60 min | Reference | Reference | Reference | Reference |
>60 min | 1.23 (0.80, 1.92) | 1.07 (0.67, 1.71) | 0.8 (0.30, 2.11) | 0.55 (0.19, 1.57) |
Maternal position at birth |
Position other than lithotomy | Reference | Reference | Reference | Reference |
Lithotomy | 1.46 (1.01, 2.11)* | 0.87 (0.56, 1.35) | 1.91 (0.90, 4.05) | 1.16 (0.44, 3.03) |
Mode of delivery |
Spontaneous | Reference | Reference | Reference | Reference |
Vacuum extraction | 3.37 (1.92, 5.93)* | 3.28 (1.73, 6.21)* | 4.92 (2.04, 11.84)* | 4.31 (1.49, 12.5)* |
Fetal scalp electrode |
No | Reference | Reference | Reference | Reference |
Yes | 1.44 (0.99, 2.08) | 1.24 (0.81, 1.89) | 2.76 (1.23, 6.19)* | 2.31 (0.93, 5.70) |
Fetal presentation |
Occiput anterior | Reference | Reference | Reference | Reference |
Occiput posterior | 1.37 (0.50, 3.74) | 1.44 (0.50, 4.16) | 3.24 (0.80, 13.22) | 3.98 (0.82, 19.20) |
Hand or arm presenting fetal part |
No | Reference | NE | Reference | NE |
Yes | 0.99 (0.55, 1.76) | NE | 0.77 (0.22, 2.68) | NE |
Fetal weight |
≤4000 g | Reference | Reference | Reference | Reference |
>4000 g | 2.56 (1.44, 4.57)* | 2.26 (1.22, 4.19)* | 5.66 (2.39, 13.40)* | 5.93 (2.29, 15.33)* |
Fetal head circumference |
≤35 cm | Reference | NE | Reference | NE |
>35 cm | 1.91 (1.31, 2.77)* | NE | 3.58 (1.55, 8.27)* | NE |
Unadjusted and adjusted odds ratios for risk factors for perineal tear using multinomial logistic regression. The group of women with second-degree perineal tear and OASI were compared with women with no or first-degree perineal. aHeredity of pelvic floor dysfunction and/or connective tissue deficiency; *Significant at level p < 0.05. aOR, adjusted odds ratio; BMI, body mass index; CI, confidence interval; GA, gestational age; NE, not estimated; OASI, obstetric anal sphincter injury; OR, odds ratio; SUI, stress urinary incontinence. |
Insert Table 4 approximately here.
Odds ratios for high vaginal tear
Table 5 shows the unadjusted and adjusted odds ratios for high vaginal tear. Women with a high vaginal tear were more likely to report heredity of pelvic floor dysfunction and/or connective tissue deficiency, to have induced labor, to deliver a baby whose hand or arm was the presenting fetal part, and to deliver a baby whose head circumference exceeded 35 cm, compared to referent women with no or low vaginal tear. After adjustment, heredity of pelvic floor dysfunction and/or connective tissue deficiency, induced labor, and fetal head circumference > 35 cm remained as risk factors significantly increasing the risk of high vaginal tear. In the adjusted model, augmentation of oxytocin significantly reduced the risk of high vaginal tear despite not being significant in the unadjusted model.
Table 5
Unadjusted and adjusted odds ratio for the risk of high vaginal tear
n = 426 | OR (95% CI) | aOR (95% CI) |
Age | | |
≤25 years | Reference | Reference |
>25 years | 2.26 (0.87, 5.87) | 2.44 (0.80, 7.47) |
BMI | | |
≤25 kg/m2 | Reference | Reference |
25.1–30 kg/m2 | 1.08 (0.55, 2.14) | 1.10 (0.52, 2.34) |
>30 kg/m2 | 0.93 (0.37, 2.34) | 0.80 (0.29, 2.20) |
Education | | |
9 to < 12 years | 1.49 (0.16, 13.70) | 6.18 (0.48, 78.82) |
12 years | 0.69 (0.36, 1.32) | 0.88 (0.43, 1.79) |
University | Reference | Reference |
Hereditya | | |
No | Reference | Reference |
Yes | 2.18 (1.11, 4.29)* | 2.33 (1.09, 5.00)* |
SUI in late pregnancy | | |
No | Reference | NE |
Yes | 0.79 (0.37, 1.69) | NE |
GA at birth | | |
Preterm and term | Reference | Reference |
Postterm | 2.02 (0.91, 4.50) | 0.63 (0.22, 1.82) |
Delivery start | | |
Spontaneous | Reference | Reference |
Induction | 2.82 (1.52, 5.25)* | 3.64 (1.54, 8.59)* |
Epidural analgesia | | |
No | Reference | Reference |
Yes | 0.89 (0.50, 1.56) | 0.73 (0.38, 1.39) |
Oxytocin stimulation | | |
No | Reference | Reference |
Yes | 0.87 (0.49, 1.52) | 0.44 (0.21, 0.90)* |
Duration of active 2nd stage | | |
≤15 min | 0.63 (0.27, 1.48) | 0.67 (0.27, 1.64) |
16–60 min | Reference | Reference |
>60 min | 1.03 (0.54, 1.99) | 0.91 (0.44, 1.89) |
Maternal position at birth | | |
Position other than lithotomy | Reference | Reference |
Lithotomy | 1.3 (0.74, 2.30) | 1.10 (0.55, 2.19) |
Mode of delivery | | |
Spontaneous | Reference | Reference |
Vacuum extraction | 1.53 (0.78, 3.02) | 2.32 (0.97, 5.56) |
Fetal scalp electrode | | |
No | Reference | Reference |
Yes | 1.62 (0.90, 2.90) | 1.74 (0.87, 3.48) |
Fetal presentation | | |
Occiput anterior | Reference | Reference |
Occiput posterior | 0.43 (0.06, 3.32) | 0.48 (0.05, 5.06) |
Hand or arm presenting fetal part | | |
No | Reference | Reference |
Yes | 2.14 (1.02, 4.48)* | 2.20 (0.96, 5.05) |
Fetal weight | | |
≤4000 g | Reference | NE |
>4000 g | 1.15 (0.63, 2.11) | NE |
Fetal head circumference | | |
≤35 cm | Reference | Reference |
>35 cm | 2.55 (1.35, 4.83)* | 2.86 (1.43, 5.75)* |
Unadjusted and adjusted odds ratio for the risk of high vaginal tear using logistic regression. The group of women with high vaginal tear was compared with women with none or low vaginal tear. aHeredity of pelvic floor dysfunction and/or connective tissue deficiency; *Significant at level p < 0.05. aOR, adjusted odds ratio; BMI, body mass index; CI, confidence interval; GA, gestational age; NE, not estimated; OR, odds ratio; SUI, stress urinary incontinence. |
Insert Table 5 approximately here.
Odds ratios for the combined effect of delivery mode and fetal weight on the risk of perineal tear
Table 6 shows the odds ratios, before and after adjustment, for second-degree perineal tear and OASI, in four different combinations of two risk factors - vacuum extraction and fetal weight: 1) women with spontaneous delivery of a child weighing < 4000 g, 2) women with spontaneous delivery of a child weighing ≥ 4000 g, 3) women with vacuum-assisted delivery of a child weighing < 4000 g, and 4) women with vacuum-assisted delivery of a child weighing ≥ 4000 g. Subgroup 4, in which the two major risk factors were combined, had adjusted ORs for second-degree tear and OASI of 5.4 (95% CI: 1.4, 20.6) and 10.5 (95% CI: 1.4, 80.8), respectively, and the interaction terms for second-degree perineal tear and for OASI were 0.66 (95% CI: 0.14–3.2) and 0.2 (95% CI: 0.02–2.03) respectively, meaning that there was no significant interaction between vacuum extraction and fetal birthweight above 4000 g (data not shown).
Table 6
Unadjusted and adjusted odds ratios for the risk of second-degree perineal tear and obstetric anal sphincter injury by delivery mode and fetal weight.
n = 489 | Second-degree perineal tear | Obstetric anal sphincter injury |
| Incidence (n) | OR (95% CI) | aOR (95% CI) | Incidence (n) | OR (95% CI) | aOR (95% CI) |
Spontaneous delivery and fetal weight < 4000 g (n = 355) | 142 | Reference | Reference | 14 | Reference | Reference |
Spontaneous delivery and fetal weight ≥ 4000 g (n = 54) | 29 | 2.54 (1.33, 4.85) | 2.35 (1.20, 4.63) | 9 | 6.00 (2.50, 14.0) | 8.30 (2.90, 23.50) |
Vacuum extraction and fetal weight < 4000 g (n = 63) | 39 | 3.42 (1.84, 6.35) | 3.44 (1.72, 6.88) | 8 | 7.11 (2.60, 19.45) | 6.30 (1.94, 20.41) |
Vacuum extraction and fetal weight ≥ 4000 g (n = 17) | 12 | 5.61 (1.55, 20.23) | 5.40 (1.40, 20.60) | 2 | 9.48 (1.46, 61.45) | 10.50 (1.40, 80.80) |
Unadjusted and adjusted odds ratios for the risk of second-degree perineal tear and obstetric anal sphincter injury by delivery mode (spontaneous or vacuum extraction) and fetal weight (< 4000 g or ≥ 4000 g). aOR, adjusted odds ratio; CI, confidence interval; OR, odds ratio. |
Insert Table 6 approximately here.