Table 1. Characteristics of study cohort by planned mode of delivery after previous cesarean section.
| ERCS n (%)a, unless otherwise stated (n = 45,579) | Planned VBAC n (%)a, unless otherwise stated (n = 28,464) | |
|---|---|---|
| Sociodemographic characteristics | ||
| Maternal age (years) | ||
| Less than 25 | 4,372 (9.6) | 3,546 (12.5) |
| 25–29 | 10,104 (22.2) | 6,698 (23.5) |
| 30–34 | 15,854 (34.8) | 9,994 (35.1) |
| 35–39 | 12,249 (26.9) | 6,856 (24.1) |
| 40 or more | 3,000 (6.6) | 1,370 (4.8) |
| Median (IQR) maternal age (years) | 32 (28–36) | 32 (28–35) |
| Mother’s country of birth | ||
| UK | 40,420 (88.7) | 24,814 (87.2) |
| Non-UK | 5,159 (11.3) | 3,650 (12.8) |
| Marital status/registration type | ||
| Married or joint registration/same address | 40,786 (89.5) | 25,290 (88.8) |
| Joint registration/different address | 3,321 (7.3) | 2,100 (7.4) |
| Sole registration | 1,472 (3.2) | 1,074 (3.8) |
| Socioeconomic statusb | ||
| Managerial/professional | 21,951 (48.2) | 13,230 (46.5) |
| Intermediate | 10,115 (22.2) | 5,988 (21.0) |
| Routine/manual | 11,678 (25.6) | 7,819 (27.5) |
| Otherc | 1,835 (4.0) | 1,427 (5.0) |
| Maternal medical and pregnancy-related characteristics | ||
| Number of previous cesarean sections | ||
| 1 | 33,956 (74.5) | 27,509 (96.6) |
| 2 or more | 11,623 (25.5) | 955 (3.4) |
| Median (IQR) number of previous cesarean sections | 1 (1–2) | 1 (1–1) |
| Any prior vaginal deliveryΨ | ||
| No | 37,523 (82.7) | 17,380 (61.2) |
| Yes | 7,874 (17.3) | 10,997 (38.8) |
| Interpregnancy interval (months)Ψ | ||
| 24 or more | 25,321 (60.0) | 13,720 (56.4) |
| 12–23 | 10,939 (25.9) | 6,700 (27.5) |
| Less than 12 | 5,927 (14.0) | 3,915 (16.1) |
| Median (IQR) interpregnancy interval (months)Ψ | 29 (17–50) | 27 (16–48) |
| Mother smoked at bookingΨ | ||
| No | 34,991 (83.3) | 20,677 (78.2) |
| Yes | 7,028 (16.7) | 5,773 (21.8) |
| Maternal BMI at booking (kg/m2)Ψ | ||
| Less than 25 | 11,957 (35.9) | 8,741 (46.6) |
| 25–29.9 | 10,181 (30.5) | 5,738 (30.6) |
| 30 or more | 11,194 (33.6) | 4,294 (22.9) |
| Median (IQR) BMI at booking (kg/m2)Ψ | 27 (24–32) | 25 (23–29) |
| Hypertensive disorder | 2,258 (5.0) | 1,634 (5.7) |
| Diabetes | 1,960 (4.3) | 479 (1.7) |
| Prelabor rupture of membranes | 451 (1.0) | 2,448 (8.6) |
| Infant-related characteristics | ||
| Male infant | 23,218 (50.9) | 14,651 (51.5) |
| Gestational age at delivery (weeks) | ||
| 39–41 | 31,880 (69.9) | 22,758 (80.0) |
| 37–38 | 13,699 (30.1) | 5,706 (20.0) |
| Median (IQR) gestational age at delivery (weeks) | 39 (38–39) | 40 (39–40) |
| Birth weight centiled | ||
| 10th–90th | 35,930 (79.3) | 22,928 (80.8) |
| Less than 10th | 2,640 (5.8) | 2,890 (10.2) |
| More than 90th | 6,749 (14.9) | 2,555 (9.0) |
aPercentage of those with complete data.
bSocioeconomic status of mother for sole registered birth or highest of mother’s or father’s socioeconomic status for births registered inside marriage or jointly registered by both parents outside marriage. Socioeconomic status defined by NS-SEC based on occupation and employment status.
cOther includes never worked/long-term unemployed, student, not stated, or not classifiable.
dDerived from gestational age at delivery, birth weight, and gender of child using sex-specific birth weight for gestational age centiles as reported by Bonellie and colleagues [33].
ΨMissing data: any prior vaginal delivery 269 (0.36%); interpregnancy interval 7,521 (10.16%); maternal smoking status 5,574 (7.53%); maternal BMI 21,938 (29.63%); birth weight centile 351 (0.47%).
Abbreviations: ERCS, elective repeat cesarean section; IQR, interquartile range; NS-SEC, National Statistics Socio-Economic Classification; VBAC, vaginal birth after previous cesarean