Advanced cervical dilatation as a predictor for low emergency cesarean delivery: a comparison between migrant and non-migrant Primiparae – secondary analysis in Berlin, Germany

Rates of cesarean delivery worldwide are high and still rising. Depending on study region rates between 27.3 and 33.0% are reported [1‐7]. Evidence shows that cesarean rates are higher in women admitted to the labor ward during the early stages of labor (i.e. with beginning cervical dilatation) than in those who were admitted at a later stage (i.e. with advanced cervical dilatation) [8‐11], e.g. 10.3% vs. 4,2% [8] and 21.8% vs. 14.5% [11]. Moreover, Cheng et al. [12] found an increasing risk of cesarean delivery in association with the length of the first stage of labor; the longer the first stage, the higher the risk.

Cesarean rates are often higher in women who immigrated than in women born in the receiving country [13]. However, rates are not homogeneous in immigrant women of different origin. For example, women from sub-Saharan Africa are more likely to deliver by cesarean delivery than immigrant women from other low- and middle-income countries [14]. Disparities in cesarean birth rates between immigrant and non-immigrant women may occur because of non-medical factors such as communication barriers, less support and/or care practices during labor and delivery, female genital cutting, or cultural preference [15‐17]. A different ethnicity or race thus is seen as a risk marker for cesarean delivery in women even if they have no obstetric risk factors [18, 19].

Findings regarding migrant status as risk factor for cesarean delivery are not consistent, however. David et al. [20] report that 1st generation immigrant women from Turkey and Lebanon delivering in Berlin/Germany had considerably lower crude rates of cesarean delivery (21.9 and 22.2%) than non-immigrant women (39.2%); the cesarean rates among 2nd and 3rd generation women were similar to those of non-immigrant women. To identify possible reasons for these unexpected findings we here assess 1) whether immigrant women from Turkey and Lebanon were admitted during later stages of labor (measured by advanced cervical dilatation) than non-immigrant women; and 2) whether later admission can explain lower cesarean rates in immigrant women – taking potential confounders (age, educational attainment, body weight, oxytocic agent) into account.

Characteristics of the study population are provided in Table 1. There are noticeable differences in the distribution of age and educational level between the immigrant and non-immigrant women. Differences in obesity (BMI > =30 kg/m2) prevalence between migrant and non-immigrant women were small. 55.6% of Turkish migrant women, 45.8% of Lebanese migrant women, and 50.6% of non-immigrant women received oxytocic agents. At the time of admission to labor ward, a smaller proportion of Turkish migrant women (15.8%) were in the active phase of labor, compared to Lebanese (26.4%) and non-immigrant women (26.1%). Emergency cesarean delivery rates were lower in both immigrant groups (Turkish: 15.8%; Lebanese: 13.9%) compared to non-immigrant women (23.9%). Indications for an emergency cesarean delivery were among others failure to progress in labor, multiple birth, macrosomia combined with gestational diabetes, maternal diseases such as pre-eclamsia, s/p cesarean delivery, and anomalies of fetal presentation.

Figure 2 shows that cervical dilatation at admission most often is between 0 cm and 3 cm (before or in latency phase of labor). Overall, only small differences can be observed between immigrant and non-immigrant women, (Turkish origin vs. non-migrant women: chi-square test p < 0.01, Lebanese origin vs. non-migrant women: chi-square test p = 0.95), providing no evidence of a later admittance of 1st generation Lebanese migrant women but evidence for an earlier admittance of 1st generation Turkish migrant women (0 cm - 3 cm vs. 4 cm - 10 cm). When cervical dilatation was used as a continuous variable (0 cm - 10 cm), no statistically significant differences were found (Turkish origin vs. non-migrant women: Kruskal-Wallis test (median) p = 0.20; Lebanese vs. non-migrant women: Kruskal-Wallis test (median) p = 0.11). Women with premature rupture of the membranes are known for early admission. In our study 28.5% (335 of 1174) of women without premature rupture and 8.4% of women with a premature rupture admitted with > = 4 cm of cervical dilatation. A cesarean was performed in 23.1% of women without and 20.5% of women with premature rupture of membranes.

The most important obstetric complication is a hemorrhage (23 women). Pathological cardiotocography (CTG) or auscultatory bad fetal heart tones is ranked first of indications for cesarean (Table 2).

In the logistic regression analysis, advanced cervical dilatation (inverse association with an adjusted Odds Ratio (aOR) of 0.76, 95% CI: 0.70–0.82), maternal age (aOR: 1.06, 95% CI: 1.04–1.09), the application of oxytocic agents (inverse association with an aOR of 0.55, 95% CI: 0.42–0.72), and a BMI ≥30 (aOR: 2.25, 95% CI: 1.51–3.34) are statistically significantly associated with the outcome “emergency cesarean delivery” (Table 3).

In addition, standardized estimates show that higher cervical dilatation is the most relevant predictor of an emergency cesarean delivery, followed by a BMI of 30 or above (Table 3).

Sensitivity analysis: Results of analysis with complete data show no substantial differences compared with the results of the imputed data set. This demonstrates that results are only slightly sensitive on changes in the study population.

At the time of admission to labor ward, a smaller proportion of Turkish migrant women was in the active phase of labor, compared to women of Lebanese origin and non-immigrant women. In the logistic regression analysis cervical dilatation was found to be the most relevant predictor of a cesarean delivery. Still, rates of cesarean deliveries were lower in women of Turkish and Lebanese origin than in non-immigrant women.

Early admission to delivery room before or in the latency phase (cervical dilatation of less than 4 cm) can lead to a mistaken diagnosis of failure to progress in labor [22]. This risk factor by now is well documented, but it continues to be observed in nulliparous women, even in the high-standard secondary and tertiary hospitals of Berlin/Germany participating in our study. Underlying may be expectations of observing a dilatation of 1 cm/hour, which are unreasonable for the actual, early stage of labor. This may lead to an overdiagnosis of dystocia and, subsequently, to an overuse of interventions aimed at accelerating labor progress – and ultimately to an emergency cesarean delivery [8, 10, 22, 23].

Cesarean deliveries are considered safe, but there are several risks associated with this procedure like infections, bleedings, allergic reactions to anesthetics, problems with the placenta in future deliveries or possible injuries to newborn.

A higher frequency of emergency cesarean deliveries among immigrants and ethnic minorities has been observed in several studies [24‐27]; however, it tends to differ between sub-groups, according e.g. to country of origin or duration of stay [28]. A possible explanation could be an earlier admission of nulliparous immigrant women to labor ward, e.g. because of actual or expected communication problems. In our study, however, we did not find evidence for the hypothesis that 1st generation immigrant women would generally be admitted to labor ward at earlier stages of labor (as measured by cervical dilatation) than non-immigrant women. There is some evidence that this may be the case for Turkish, but not for Lebanese women: A larger proportion of Turkish nulliparous women is admitted to labor ward before the onset of the active phase, and the proportion of deliveries by vacuum extraction is twice as high as among Lebanese women. Nevertheless, crude cesarean delivery rates are considerably lower among women from Turkey and Lebanon compared to non-immigrant women. A lower chance of cesarean delivery remains visible in the logistic regression analysis but fails to reach statistical significance in our sample. Thus, the lower rates of cesarean delivery reported by David et al. [20] in the full data set of this study cannot be explained by later admission of 1st generation migrant women (at least not from Turkey and Lebanon) or by the immigrant status itself. Other factors not considered in this paper must therefore play a role, such as multiparity. The strengths of the study are the high participation rate (which makes selection bias unlikely) and the availability of detailed data from interviews and clinical documentation of perinatal variables. Sectio rates are lower than reported in the literature, which is attributable to the inclusion and exclusion criteria applied to this sample (see flowchart).

The main limitation is the sample size available for analysis due to exclusion criteria necessary to examine the study hypothesis. The cesarean delivery rates reported here are unlikely to be biased with regard to our study question. Exclusion criteria relate mainly to previous deliveries and different migration histories; the exclusion of women with elective cesarean deliveries is necessary because they are obviously not informative with regard to cervical dilatation. Moreover, given the heterogeneity of the immigrant population in Germany in terms of country of birth, migration background, and ethnicity, findings cannot be generalized to all immigrant women. Another limitation is that the sample is not representative for all German maternity hospitals; the way deliveries are organized may vary, thus incurring differing risks of emergency cesarean deliveries.

Turkish migrant women were more likely to have instrumental delivery compared to non-immigrant women, although cesarean delivery rates were certainly lower. This might suggest that other confounding factors help Turkish migrant women deliver instrumentally and may make the relationship between later admission and lower cesarean delivery rates in immigrant women obscure.

Advanced cervical dilatation at the time of admission to labor ward does not explain lower emergency cesarean delivery rates in Turkish and Lebanese migrant women, despite the fact that this is the strongest among the predictors for emergency cesarean delivery considered in this study: With early admission, the chance of cesarean delivery increases, irrespective of migrant status. Obesity (BMI ≥30 kg/m²) and later maternal age follow in second and third place.