Nuffield Department of Women's Reproductive Health, John Radcliffe Hospital, Oxford University, Oxford, United Kingdom.
Oxford Fetal Medicine Unit, John Radcliffe Hospital, Headley Way, Oxford, United Kingdom.
PLoS Med. 2021 Jan 15;18(1):e1003503. doi: 10.1371/journal.pmed.1003503. eCollection 2021 Jan.
Breech presentation at term contributes significantly to cesarean section (CS) rates worldwide. External cephalic version (ECV) is a safe procedure that reduces term breech presentation and associated CS. A principal barrier to ECV is failure to diagnose breech presentation. Failure to diagnose breech presentation also leads to emergency CS or unplanned vaginal breech birth. Recent evidence suggests that undiagnosed breech might be eliminated using a third trimester scan. Our aim was to evaluate the impact of introducing a routine 36-week scan on the incidence of breech presentation and of undiagnosed breech presentation.
We carried out a population-based cohort study of pregnant women in a single unit covering Oxfordshire, United Kingdom. All women delivering between 37+0 and 42+6 weeks gestational age, with a singleton, nonanomalous fetus over a 4-year period (01 October 2014 to 30 September 2018) were included. The mean maternal age was 31 years, mean BMI 26, 44% were nulliparous, and 21% were of non-white ethnicity. Comparisons between the 2 years before and after introduction of routine 36-week scan were made for 2 primary outcomes of (1) the incidence of breech presentation and (2) undiagnosed breech presentation. Secondary outcomes related to ECV, mode of birth, and perinatal outcomes. Relative risks (RRs) with 95% confidence intervals (CIs) are reported. A total of 27,825 pregnancies were analysed (14,444 before and 13,381 after). A scan after 35+0 weeks was performed in 5,578 (38.6%) before, and 13,251 (99.0%) after (p < 0.001). The incidence of breech presentation at birth did not change significantly (2.6% and 2.7%) (RR 1.02; 95% CI 0.89, 1.18; p = 0.76). The rate of undiagnosed breech before labour reduced, from 22.3% to 4.7% (RR 0.21; 95% CI 0.12, 0.36; p < 0.001). Vaginal breech birth rates fell from 10.3% to 5.3% (RR 0.51; 95% CI 0.30, 0.87; p = 0.01); nonsignificant increases in elective CS rates and decreases in emergency CS rates for breech babies were seen. Neonatal outcomes were not significantly altered. Study limitations include insufficient numbers to detect serious adverse outcomes, that we cannot exclude secular changes over time which may have influenced our results, and that these findings are most applicable where a comprehensive ECV service exists.
In this study, a universal 36-week scan policy was associated with a reduction in the incidence but not elimination of undiagnosed term breech presentation. There was no reduction in the incidence of breech presentation at birth, despite a comprehensive ECV service.
足月臀位分娩显著增加了全世界剖宫产率。经阴道外转胎位术（ECV）是一种安全的降低足月臀位分娩和相关剖宫产率的方法。ECV 的主要障碍是未能诊断出臀位。未能诊断出臀位也会导致紧急剖宫产或计划外的阴道臀位分娩。最近的证据表明，使用孕晚期的 3 维超声检查可以消除未诊断的臀位。我们的目的是评估在常规 36 周扫描中引入后对臀位和未诊断的臀位发生率的影响。
我们对英国牛津郡一个单一单位的孕妇进行了基于人群的队列研究。在 4 年期间（2014 年 10 月 1 日至 2018 年 9 月 30 日），所有在 37+0 至 42+6 周妊娠期分娩的单胎、非畸形胎儿的孕妇都被纳入。孕妇的平均年龄为 31 岁，平均 BMI 为 26，44%是初产妇，21%是非白人。比较了引入常规 36 周扫描前后的 2 个主要结局（1）臀位分娩的发生率和（2）未诊断的臀位分娩的发生率。与 ECV、分娩方式和围产期结局相关的次要结局。报告了相对风险（RR）及其 95%置信区间（CI）。共分析了 27825 例妊娠（14444 例在扫描前，13381 例在扫描后）。在扫描前，有 5578 例（38.6%）在 35+0 周后进行了扫描，在扫描后，有 13251 例（99.0%）进行了扫描（p<0.001）。臀位分娩的发生率无明显变化（2.6%和 2.7%）（RR 1.02；95%CI 0.89，1.18；p=0.76）。在未发生分娩前，未诊断的臀位比例从 22.3%下降到 4.7%（RR 0.21；95%CI 0.12，0.36；p<0.001）。阴道臀位分娩率从 10.3%下降到 5.3%（RR 0.51；95%CI 0.30，0.87；p=0.01）；剖宫产率的显著增加和臀位婴儿的紧急剖宫产率的下降。新生儿结局没有明显改变。研究的局限性包括没有足够的数量来检测严重的不良结局，我们不能排除随着时间的推移可能发生的长期变化，这些发现最适用于存在全面的 ECV 服务的地方。
在这项研究中，普遍的 36 周扫描政策与未诊断的足月臀位分娩发生率的降低有关，但不能消除。尽管有全面的 ECV 服务，但臀位分娩的发生率并没有降低。
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