Plain English summary
Pregnancies beyond 41 completed weeks are associated with adverse outcomes. Hence, the World Health Organization recommends inducing labour for women who have reached 41 completed weeks of pregnancy without spontaneous labour pain. Many of such women and/or their clinicians do not want to induce, instead they prefer to deliver by caesarean section or expectant management (awaiting spontaneous onset of labour).
We compared pregnancy outcomes of women at 41 completed weeks of pregnancy by three different managements – induction of labour, elective caesarean section and expectant management using two large, WHO databases conducted in Africa, Asia, Latin America and the Middle East. We did not find any difference in adverse pregnancy outcomes between induction group and expectant group except higher caesarean section rate in induction of labour group.
We found that neonatal intensive care unit admission was higher in newborns delivered by elective caesarean section compared to that of induction of labour. Our findings showed that elective caesarean section had increased risk of adverse neonatal outcomes and should not be recommended. However, the choice between induction of labour and expectant management should be cautiously considered since the available evidences are still quite limited.
Background
The World Health Organization (WHO) recommends induction of labour (IOL) for women who have reached 41 completed weeks of pregnancy without spontaneous onset of labour [
1]. Rates of IOL vary across countries. IOL rates for high-income countries were 23.4% of deliveries in United States in 2010 [
2], 22.1% of deliveries in England between 2011 and 2012 [
3] and 25.4% of deliveries in Australia in 2010 [
4]. The rates also vary for low and middle-income countries (LMIC). The WHO Global Survey on Maternal and Perinatal Health reported the prevalence of IOL in facility deliveries as 4.4% in seven African countries, 12.1% in nine Asian countries [
5] and 11.4% in eight Latin American countries [
6]. IOL is specifically recommended to prevent complications of prolonged pregnancy, such as increased perinatal mortality, stillbirth, fetal growth restriction, meconium aspiration syndrome and macrosomia [
7‐
10]. However, IOL itself carries the risk of uterine hyperstimulation, increased instrumental delivery, uterine rupture, fetal distress and Caesarean section (CS) [
1].
Many women with prolonged pregnancy (≥41 weeks) and/or their clinicians often elect not to induce, and chose either ECS or expectant management EM (awaiting spontaneous onset of labour). The reasons for choosing CS may be not only to manage the prolonged pregnancy, but also be the preferred mode of delivery for the women and/or the clinicians [
11].
Systematic reviews of randomized controlled trials have compared the risks and benefits of IOL compared to EM at and beyond 41 weeks gestation [
12‐
16]. All these systematic reviews assessed perinatal death and CS rate as primary outcomes, and other maternal and perinatal morbidities such as postpartum haemorrhage, ruptured uterus, meconium aspiration, Apgar score, NICU admission, stillbirth and early neonatal death as secondary outcomes. These reviews consistently reported that IOL at 41 completed weeks of gestation reduced the complications of postterm pregnancies compared to EM. However, the risks and benefits of IOL compared to ECS for women with prolonged pregnancy have not been as thoroughly explored. Furthermore, analysis of clinical data can provide insight into the effectiveness of interventions in “real life” settings. This analysis aimed to explore not only the risks and benefits of IOL but also that of ECS regarding to pregnancy outcomes among women with prolonged pregnancy in two large multi-country databases of facility deliveries in predominantly low- and middle-income countries.
Results
The prevalence of prolonged pregnancy at facility setting in WHOGS, WHOMCS and combined databases were 7.9% (18,331/232917), 7.5% (18,312/245546) and 7.7% (36,643/478463), respectively.
A total of 33,003 singleton pregnant women (16,148 women from WHOGS and 16,855 women from WHOMCS) with prolonged pregnancy (≥41 completed weeks) were included in this analysis. Median gestational age for this cohort was 41 and 95% CIs were 41–43 weeks. Amongst them, 13.1% (
n = 4332) were delivered by IOL, 5.9% (
n = 1951) were delivered by elective or prelabour CS and 80.9% (
n = 26,720) were in EM group. Details are presented in Fig.
1.
The details of maternal and neonatal characteristics among the three different management groups for WHOGS and WHOMCS are presented in Table
2. We found that pregnant women were significantly different with respect to maternal age, education, parity, previous CS and newborns birth weight among the three different management groups in both WHOGS and WHOMCS but marital status was significantly different only in WHOGS.
Table 2
Maternal and neonatal characteristics of three different management groups for WHOGS and WHOMCS databases
Maternal characteristics |
Age (Years) |
≤ 19 | 168 (7.9) | 53 (7.7) | 1578 (11.8) | < 0.001 | 222 (10.0) | 104 (8.3) | 1532 (11.5) | 0.003 |
20–34 | 1786 (84.3) | 571 (82.6) | 10,623 (79.7) | 1801 (81.4) | 1035 (82.1) | 10,606 (79.3) |
≥ 35 | 165 (7.8) | 67 (9.7) | 1137 (8.5) | 190 (8.6) | 121 (9.6) | 1244 (9.3) |
Education (School years) |
< 7 | 412 (20.0) | 119 (17.3) | 3218 (24.3) | < 0.001 | 290 (13.1) | 195 (15.4) | 2854 (21.3) | < 0.001 |
7–12 | 1173 (56.9) | 409 (59.4) | 7842 (59.3) | 1151 (52.0) | 728 (57.8) | 7671 (57.3) |
> 12 | 476 (23.1) | 161 (23.4) | 2176 (16.4) | 772 (34.9) | 337 (26.8) | 2857 (21.4) |
Marital |
With partner | 1954 (92.3) | 620 (90.0) | 11,663 (87.5) | < 0.001 | 1944 (87.8) | 1119 (88.8) | 11,812 (88.3) | 0.692 |
Without partner | 164 (7.7) | 69 (10.0) | 1660 (12.5) | 269 (12.2) | 141 (11.2) | 1570 (11.7) |
Parity |
Primiparous | 1223 (57.7) | 372 (53.8) | 6353 (47.6) | < 0.001 | 1304 (59.0) | 797 (63.3) | 6496 (48.6) | < 0.001 |
Multiparous | 896 (42.3) | 319 (46.2) | 6985 (52.4) | 908 (41.0) | 462 (36.7) | 6879 (51.4) |
Previous CS |
Yes | 43 (2.0) | 171 (24.7) | 731 (5.5) | < 0.001 | 75 (3.4) | 259 (20.7) | 879 (6.6) | < 0.001 |
No | 2076 (98.0) | 520 (75.3) | 12,607 (94.5) | 2135 (96.6) | 993 (79.3) | 12,480 (93.4) |
Neonatal characteristics |
Birth weight |
< 2500 g | 57 (2.7) | 9 (1.3) | 359 (2.7) | < 0.001 | 71 (3.2) | 33 (2.6) | 448 (3.4) | < 0.001 |
2500–4000 g | 1970 (93.0) | 585 (84.7) | 12,220 (91.6) | 2017 (91.1) | 1084 (86.0) | 12,208 (91.2) |
> 4000 g | 92 (4.3) | 97 (14.0) | 758 (5.7) | 125 (5.7) | 143(11.4) | 726 (5.4) |
Adverse maternal outcomes among different management groups
Table
3 showed comparison of adverse maternal outcomes among different management groups for WHOGS, WHOMCS and combined database, respectively. The association could not be assessed for ruptured uterus and ICU admission outcomes in WHOMCS as women with these outcomes were found only in EM group. In combined database, increased risk of ruptured uterus outcome was not statistically significant for EM compared to IOL (aOR 1.98; 95% CI: 0.51–7.65). EM was significantly associated with decreased risk of CS rate consistently in both databases i.e. (aOR0.76; 95% CI: 0.66–0.87) in WHOGS, (aOR0.67; 95% CI: 0.59–0.76) in WHOMCS and (aOR0.70; 95% CI: 0.64–0.77) in combined database, compared to IOL.
Table 3
Adverse maternal outcomes among different management groups in WHOGS, WHOMCS and Combined databases
PPH |
IOL | 88/2119 (4.2) | 1 | 1 | 38/2213 (1.7) | 1 | 1 | 126/4332 (2.9) | 1 | 1 |
ECS | 11/691 (1.6) | 0.78 (0.39, 1.56) | 0.66 (0.30, 1.44) | 19 /1260 (1.5) | 1.01 (0.54, 1.87) | 0.99 (0.50, 1.98) | 30 /1951 (1.5) | 1.01 (0.66, 1.53) | 0.89 (0.56, 1.43) |
EM | 542/13338 (4.1) | 1.12 (0.84, 1.51) | 1.21 (0.86, 1.70) | 173/13382 (1.3) | 0.88 (0.58, 1.33) | 0.91 (0.57, 1.45) | 715/26720 (2.7) | 1.03 (0.82, 1.29) | 1.03 (0.80, 1.33) |
Ruptured uterus |
IOL | 3/2119 (0.5) | 1 | 1 | 0/2213 (0.0) | – | – | 3/4332 (0.1) | 1 | 1 |
ECS | 2/691 (0.3) | 0.65 (0.10, 4.04) | 0.40 (0.05, 3.22) | 0 /1260 (0.0) | – | – | 2 /1951 (0.1) | 0.74 (0.15, 3.60) | 0.48 (0.07, 3.05) |
EM | 40/13338 (1.2) | 2.70 (0.79, 9.28) | 1.52 (0.32, 7.16) | 10/13382 (0.1) | – | – | 50/26720 (0.3) |
3.29 (1.16, 9.33)
| 1.98 (0.51, 7.65) |
Admission to ICU |
IOL | 24/2119 (1.1) | 1 | 1 | 0/2213 (0.0) | – | – | 24/4332 (0.6) | 1 | 1 |
ECS | 5/691 (0.7) | 1.85 (0.58, 5.88) | 1.17 (0.35, 4.03) | 0 /1260 (0.0) | – | – | 5 /1951 (0.3) | 1.21 (0.49, 2.96) | 1.09 (0.36, 3.31) |
EM | 258/13338 (1.9) | 0.62 (0.37, 1.03) | 0.60 (0.34, 1.03) | 8/13382 (0.1) | – | – | 266/26720 (1.0) | 0.69 (0.44, 1.07) | 0.66 (0.39, 1.13) |
Postpartum length of stay >7 days |
IOL | 76/2119 (3.6) | 1 | 1 | 44/2213 (2.0) | 1 | 1 | 120/4332 (2.8) | 1 | 1 |
ECS | 21/691 (3.0) |
2.18 (1.29, 3.68)
| 1.22 (0.68, 2.19) | 49 /1260 (3.9) |
2.33 (1.51, 3.60)
| 1.54 (0.96, 2.49) | 70 /1951 (3.6) |
2.16 (1.57, 2.99)
| 1.33 (0.93, 1.90) |
EM | 373/13338 (2.8) | 1.08 (0.80, 1.45) | 0.98 (0.71, 1.35) | 424/13382 (3.2) | 0.81 (0.57, 1.15) | 0.83 (0.57, 1.21) | 797/26720 (3.0) | 0.91 (0.73, 1.13) | 0.87 (0.69, 1.11) |
Severe maternal outcomec
|
IOL | 52/2119 (2.5) | 1 | 1 | 4/2213 (0.2) | 1 | 1 | 56/4332 (1.3) | 1 | 1 |
ECS | 14/691 (2.0) | 1.41 (0.73, 2.70) | 1.15 (0.57, 2.34) | 3 /1260 (0.2) | 1.41 (0.30, 6.63) | 0.64 (0.10, 3.97) | 17 /1951 (0.9) | 1.42 (0.83, 2.46) | 1.08 (0.59, 1.96) |
EM | 382/13338 (2.9) | 0.80 (0.56, 1.14) | 0.86 (0.59, 1.27) | 18/13382 (0.1) | 0.67 (0.21, 2.13) | 0.55(0.16, 1.79) | 400/26720 (1.5) | 0.77 (0.56, 1.04) | 0.80 (0.57, 1.13) |
CS rate |
IOL | 590/2119 (27.8) | 1 | 1 | 690/2213 (31.2) | 1 | 1 | 1280/4332 (29.6) | 1 | 1 |
EM | 3416/13338 (25.6) |
0.82 (0.73, 0.92)
|
0.76 (0.66,0.87)
| 3463/13382 (25.9) |
0.69 (0.61, 0.77)
|
0.67 (0.59,0.76)
| 6879/26720 (25.7) |
0.74 (0.68, 0.80)
|
0.70 (0.64,0.77)
|
Adverse perinatal outcomes among different management groups
Use of ECS was significantly associated with increased risks of NICU admission, aOR 1.76; 95%CI: 1.28–2.42 in WHOMCS and aOR 1.51; 95%CI: 1.19–1.92 in combined database, compared to IOL. The association was not statistically significant in WHOGS database. Apart from NICU outcome, the rest of perinatal outcomes were not significantly associated with different managements groups. Details are presented in Table
4.
Table 4
Adverse perinatal outcomes among different management groups in WHOGS, WHOMCS and Combined databases
APGAR <7 at 5 min |
IOL | 40/2119 (1.9) | 1 | 1 | 23/2213 (1.1) | 1 | 1 | 63/4332 (1.5) | 1 | 1 |
ECS | 3/691 (0.4) | 0.39 (0.12, 1.22) | 0.31 (0.08, 1.23) | 13/1260 (1.0) | 1.20(0.61, 2.36) | 0.92 (0.45, 1.90) | 16/1951 (0.8) | 0.81 (0.47, 1.40) | 0.67 (0.36, 1.23) |
EM | 309/13338 (2.3) | 1.10 (0.77, 1.57) | 1.21 (0.82, 1.81) | 232/13382 (1.8) | 1.41 (0.91, 2.20) | 1.39 (0.88, 2.19) | 541/26720 (2.0) | 1.19 (0.90, 1.57) | 1.27 (0.95, 1.72) |
Admission to NICU |
IOL | 146/2119 (6.9) | 1 | 1 | 101/2213 (4.6) | 1 | 1 | 247/4332 (5.7) | 1 | 1 |
ECS | 67/691 (9.7) |
1.61 (1.15, 2.26)
| 1.13 (0.75, 1.72) | 117 /1260 (9.3) |
1.99 (1.47, 2.71)
|
1.76 (1.28, 2.42) | 184/1951 (9.4) |
1.85 (1.49, 2.31)
|
1.51 (1.19, 1.92)
|
EM | 1035/13338 (7.8) | 0.94 (0.76, 1.15) | 0.99 (0.79, 1.26) | 587/13382 (4.4) | 0.90 (0.71, 1.15) | 0.92 (0.72, 1.18) | 1622/26720 (6.1) | 0.93 (0.80, 1.08) | 0.95 (0.81, 1.12) |
Stillbirth |
IOL | 10/2119 (0.5) | 1 | 1 | 8/2213 (0.4) | 1 | 1 | 18/4332 (0.4) | 1 | 1 |
ECS | 0/691 (0.0) | – | – | 4 /1260 (0.3) | 1.06 (0.31, 3.62) | 0.99 (0.27, 3.57) | 4/1951 (0.2) | 0.70 (0.24, 1.99) | 0.61 (0.20, 1.83) |
EM | 47/13338 (0.4) | 0.69 (0.33, 1.46) | 0.63 (0.29, 1.38) | 73/13382 (0.6) | 1.29 (0.60, 2.78) | 1.29 (0.56, 2.98) | 120/26720 (0.5) | 0.97 (0.58, 1.60) | 0.92 (0.54, 1.58) |
Early neonatal death |
IOL | 2/2119 (0.1) | 1 | 1 | 7/2213 (0.3) | 1 | 1 | 9/4332 (0.2) | 1 | 1 |
ECS | 1/691 (0.1) | 2.25 (0.20, 25.5) | 2.10 (0.18, 24.7) | 4 /1260 (0.3) | 1.23 (0.35, 4.35) | 0.95 (0.26, 3.45) | 5/1951 (0.2) | 1.69 (0.59, 4.85) | 1.35 (0.46, 4.00) |
EM | 50/13338 (0.4) | 4.17 (0.99, 17.5) | 3.82 (0.89, 16.2) | 67/13382 (0.5) | 1.28 (0.57, 2.91) | 1.11 (0.48, 2.56) | 117/26720 (0.4) | 1.94 (0.99, 3.80) | 1.74 (0.88, 3.45) |
Perinatal death |
IOL | 12/2119 (0.6) | 1 | 1 | 15/2213 (0.7) | 1 | 1 | 27/4332 (0.6) | 1 | 1 |
ECS | 1/691 (0.1) | 0.42 (0.06, 3.02) | 0.41 (0.05, 3.10) | 8 /1260 (0.6) | 1.15 (0.50, 2.66) | 0.96 (0.40, 2.30) | 9/1951 (0.5) | 1.06 (0.50, 2.22) | 0.90 (0.42, 1.94) |
EM | 97/13338 (0.7) | 1.27 (0.68, 2.36) | 1.18 (0.62, 2.22) | 139/13382 (1.0) | 1.20 (0.70, 2.05) | 1.14 (0.65, 2.02) | 236/26720 (0.9) | 1.26 (0.83, 1.89) | 1.19 (0.77, 1.82) |
One consideration in this analysis is that some women in the EM group may experience induction and/or CS at a later gestational age. To account for this, we re-classified those women in the EM group (at 41 completed weeks) who experienced induction or ECS later in pregnancy (i.e. beyond 41 completed weeks). There were 1759 pregnant women in the EM group with deliveries at beyond 41 weeks of gestation. They could be classified to IOL group for 1217 women and ECS group for 542 women. We did sensitivity analyses of the associations of the new classification of management groups with each pregnancy outcome in the combined database. The results showed consistent findings with our main analysis. In addition the sensitivity analyzed results provided stronger associated with increased risk of postpartum length of stay >7 days outcome (aOR1.59; 95% CI: 1.17–2.18) and admission to NICU outcome (aOR1.54; 95% CI: 1.25–1.90) for ECS compared to IOL. The stronger associated with decreased risk of severe maternal outcome (aOR0.73; 95% CI: 0.55–0.99), rate of CS (aOR0.65; 95% CI: 0.59–0.70) and admission to NICU outcome (aOR0.84; 95% CI: 0.72–0.97) were also seen for EM compared to IOL. Details are presented in Table
5. We also assessed the risk of stillbirths by week delivered using 41 weeks as a reference group. The risk was not significantly different at 42 weeks (aOR1.47; 95% CI: 0.82–2.62). However, as gestational age reached 43, 44 and 45 weeks, the risk of stillbirth were significantly increased, aOR3.45; 95% CI: 1.32–9.03 for 43 weeks, aOR 6.15; 95% CI: 1.38–27.48 for 44 weeks and aOR18.04; 95% CI: 1.96–166.11 for 45 weeks. Details are presented in Table
6.
Table 5
Adverse maternal and perinatal outcomes among different management groups in combined databases (Sensitivity analysis)
Adverse maternal outcomes |
PPH |
IOL | 168/5549 (3.03) | 1.0 | 1.0 |
ECS | 45/2493 (1.81) | 0.98 (0.69, 1.40) | 0.90 (0.61, 1.33) |
EM | 658/24,961 (2.64) | 0.87 (0.71, 1.06) | 0.88 (0.70, 1.11) |
Ruptured uterus |
IOL | 5/5549 (0.14) | 1.0 | 1.0 |
ECS | 2/2493 (0.08) | 0.42 (0.09, 1.79) | 0.21 (0.04, 1.06) |
EM | 48/24,961 (0.31) | 2.72 (1.18, 6.25) | 1.25 (0.45, 3.45) |
Admission to ICU |
IOL | 32/5549 (0.58) | 1.0 | 1.0 |
ECS | 9/2493 (0.36) | 2.06 (1.01, 4.21) | 1.56 (0.65, 3.76) |
EM | 254/24,961 (1.02) | 0.78 (0.52, 1.15) | 0.72 (0.45, 1.14) |
Postpartum stay > 7 |
IOL | 154/5549 (2.78) | 1.0 | 1.0 |
ECS | 101/2493 (4.05) | 2.48 (1.87, 3.29) | 1.59 (1.17, 2.18) |
EM | 732/24,961 (2.93) | 0.97 (0.79, 1.18) | 0.92 (0.74, 1.15) |
Severe maternal outcome |
IOL | 79/5549 (1.42) | 1.0 | 1.0 |
ECS | 24/2493 (0.96) | 1.50 (0.94, 2.40) | 1.18 (0.71, 1.96) |
EM | 370/24,961 (1.48) | 0.72 (0.54, 0.94) | 0.73 (0.55, 0.99) |
CS rate |
IOL | 1591/5549 (28.67) | 1.0 | 1.0 |
EM | 6026/24,961 (24.14) | 0.70 (0.65, 0.75) | 0.65 (0.59, 0.70) |
Adverse perinatal outcomes |
APGAR <7 at 5 min |
IOL | 109/5549 (1.97) | 1.0 | 1.0 |
ECS | 29/2493 (1.17) | 0.86 (0.56, 1.30) | 0.67 (0.41, 1.08) |
EM | 482/24,961 (1.94) | 0.88 (0.70, 1.10) | 0.97 (0.76, 1.24) |
Admission to NICU |
IOL | 344/5549 (6.22) | 1.0 | 1.0 |
ECS | 257/2493 (10.31) | 1.89 (1.57, 2.29) | 1.54 (1.25, 1.90) |
EM | 1452/24,961 (5.83) | 0.82 (0.72, 0.94) | 0.84 (0.72, 0.97) |
Stillbirth |
IOL | 25/5549 (0.45) | 1.0 | 1.0 |
ECS | 7/2493 (0.28) | 0.91 (0.40, 2.08) | 0.76 (0.30, 1.91) |
EM | 110/24,961 (0.44) | 0.94 (0.60, 1.48) | 1.01 (0.62, 1.65) |
Early neonatal death |
IOL | 23/5549 (0.42) | 1.0 | 1.0 |
ECS | 7/2493 (0.28) | 0.91 (0.39, 2.08) | 0.71 (0.30, 1.68) |
EM | 101/24,961 (0.41) | 0.93 (0.59, 1.48) | 0.82 (0.51, 1.32) |
Perinatal death |
IOL | 48/5549 (0.87) | 1.0 | 1.0 |
ECS | 14/2493 (0.56) | 0.93 (0.51, 1.69) | 0.75 (0.39, 1.43) |
EM | 210/24,961 (0.84) | 0.92 (0.66, 1.27) | 0.90 (0.63, 1.27) |
Table 6
Risk of stillbirth by week delivered
41 completed week | 95/25,631 (0.37) | 1.0 | 1.0 |
42 completed week | 32/6335 (0.51) | 1.15 (0.76, 1.71) | 1.47 (0.82, 2.62) |
43 completed week | 10/829 (1.21) | 2.91 (1.52, 5.58) | 3.45 (1.32, 9.03) |
44 completed week | 3/157 (1.91) | 4.36 (1.39, 13.64) | 6.15 (1.38, 27.48) |
45 completed week | 2/51 (3.92) | 11.12 (2.72, 45.41) | 18.04 (1.96, 166.11) |
Discussion
The prevalence of prolonged pregnancy was about 8% of total deliveries. The prevalence of prolonged pregnancy varies across the world from 3 to 12% [
25] and our analysis supports those findings. The prevalence is affected by accuracy of gestational age estimation and adoption of elective induction of labour before 41 weeks of gestation [
8]. The risk of stillbirth increased significantly when gestational age was 43 weeks or over compared to 41 weeks.
ECS was significantly associated with increased risk of adverse perinatal outcomes compared to IOL for NICU admission in WHOMCS and combined databases. Compared to IOL, EM was significantly associated with decreased risk of CS consistently in all three databases.
Four previous systematic reviews [
12,
14‐
16] reported the effect of IOL compared to EM among prolonged/post-term pregnancies. Systematic reviews of Wennerholm et al., 2009 [
15] and Sanchez-Ramos et al., 2003 [
16] reported no significant difference in perinatal deaths while those of Gülmezoglu et al., 2012 (Cochrane review) [
12] and Hussain et al., 2011 [
14] reported significantly lower perinatal death in IOL group. Three systematic reviews i.e. Sanchez-Ramos et al., Wennerholm et al. and Gülmezoglu et al. reported significant lower CS delivery rate in IOL compared to EM. These reviews support the WHO recommendation of routine use of IOL for pregnancies at 41 completed weeks. Our analysis of routinely collected data showed no significant difference in perinatal deaths, however there was a significant lower CS rate in EM compared to IOL in all databases. Possible explanations include: (1) in the Cochrane review, number of perinatal deaths were very small (only 10 deaths) but perinatal death rate of EM was 8 times more than IOL (0.32% vs. 0.04%). In our analysis, perinatal death was more common (272 deaths) but perinatal death rate of EM was only 1.4 times more than IOL (0.88% vs. 0.62%), (2) our results were from hierarchical databases and we adjusted for multiple potential confounders and clustering effects of facility and country levels in the analysis, this could lead to more conservative confidence interval and (3) the number of participants in the Cochrane review were quite similar across comparison groups but that of our study groups were quite different in number. One more explanation for the difference between our findings and the systematic reviews may relate to difference in context. Trials are generally conducted in highly controlled, often ideal settings (and often in high-resource settings), which may favour efficacy. Our data relates more to real-life practices (i.e. effectiveness) in resource-limited settings, where the intervention may not be as beneficial as trials might suggest. A recently published before and after study comparing a policy induction of labour at 41 weeks versus at 42 weeks showed a significantly lower CS rate, 15% versus 19.4% (
p = 0.0135)in a 41-week policy. There were no significant differences in maternal or neonatal outcomes [
26].
In spite of our extensive literature search, we did not identify any studies comparing IOL and ECS for women at or beyond 41 completed weeks of gestation. Similar with our results, previous study conducted among women at all gestational ages also showed that CS increased the risk of maternal and neonatal adverse outcomes [
17].
To our knowledge, this analysis was the first report of the adverse pregnancy outcomes of ECS among women with prolonged pregnancy. This study was based on two large WHO databases conducted in Africa, Asia, Latin America and the Middle East regions. Data were systematically collected by trained personnel. Thus the results of this study reflect the actual practices in participating facilities and their pregnancy outcomes in these facilities.
However, the WHO databases were collected for other specific objectives rather than to explore our study question. Moreover, the two surveys used slightly different case record forms to collect individual and institutional characteristics. Consequently, a few adverse outcomes (postpartum haemorrhage, uterine rupture and severe maternal outcome) had slightly different definitions. Despite this, we elected to combine the databases and analyzed these outcomes collectively as we regarded the outcomes as sufficiently similar.
Both databases were facility based, conducted mainly in larger, secondary and tertiary facilities where CS was available – this might lead to over-representation of adverse outcomes among women and their newborns. Thus, this study results might not be representative in smaller or different facilities. The primary data source was routine hospital records; these may not be ideal in many facility settings. Some facilities encountered suboptimal record collection such as lack of documented diagnosis. It may be due to inability to diagnose condition, failure to recognize condition or failure to document diagnosis, rather than absence of condition. To address this, several facilities adopted the study data collection form as a platform for their medical records. In the WHOMCS, in cases of unclear or missing information, medical staffs were asked to clarify information in the medical record.
The gestational age used was the best obstetric estimate based on local practices. The method of GA assessment was unknown; but usually included the calculation from last menstrual period and/or ultra-sonographic examination. Inaccurate estimate of gestational age can lead to over-estimate prolonged pregnancy [
27] and thus may have affected the results of this analysis. However, this misclassification would bias the risk assessment toward unity. The risk that we have estimated should be more conservative. We also tried to minimize the effect of gestational age inaccuracy on this analysis by excluding facilities with GA missing >5% and with unreliable information on gestational age distribution such as more than 70% of all deliveries occurred at a specific week, or where more than 30% or less than 1% of all deliveries were preterm (Fig.
1). Furthermore, data concerning with methods, types of drugs and routes of administration for IOL cervical ripening methods, oxytocin augmentation protocols, use of partogram, use of electronic fetal monitoring and epidural analgesia rates were not available in databases, so, we could not adjust for these variations to evaluate the outcomes of IOL group.
The differences in institutional intrapartum practices might influence the pregnancy outcomes. We used multilevel logistic regression model to account this effect and hierarchical survey design, using two levels (individual and facility level) for separate analysis of WHOGS and WHOMCS. Moreover, two WHO surveys conducted at different time period and the intrapartum practices of the same facilities might change in two surveys. We accounted for this effect, source of data (WHOGS and WHOMCS) as an additional level for the analysis in combined database.
In addition we did the sensitivity analyses and it showed similar associations among the three management groups when some women were reclassified based on their management beyond 41 weeks of gestation. The other limitation of this study is that it was hospital based and didn’t have information on those women who didn’t come to the hospital for delivery.
Acknowledgments
We thank WHO for giving permission to use WHOGS and WHOMCS databases. We would like to thank Dr. Cameron Hurst for giving technical guidance in multilevel modeling. We thank all members of the WHO Multi-Country Survey on Maternal and Newborn Health Research Network, including regional and country coordinators, data collection coordinators, facility coordinators, data collectors, and all staffs of the participating facilities who made the survey possible. This manuscript represents the views of the named authors only, and not the views of their institutions or organizations.