Influence of delivery characteristics and socioeconomic status on giving birth by caesarean section – a cross sectional study during 2000–2010 in Finland

Caesarean section (CS) rates vary substantially between countries, especially between low-income and high-income countries, indicating a great disparity in the availability of this life-saving obstetric procedure across the world [1‐3]. The World Health Organization (WHO) has recommended an optimal CS rate of 15% based on the CS rates of countries with the lowest maternal and neonatal mortality rates [4]. CS rates have been constantly rising in many developed countries, such as the European countries [5], especially due to the increasing tendency to perform CSs without medical indication on maternal request [6, 7]. In 2010, among the European countries, CS rates varied from 52.2% in Cyprus to 14.8% in Iceland. Only The Netherlands, Slovenia, Finland, Sweden, Iceland, and Norway had CS rates below 20% [5]. However, CS rates in Europe did not correlate with national wealth, as measured by the gross domestic product (http://​epp.​eurostat.​ec.​europa.​eu/​statistics_​explained/​index.​php/​GDP_​per_​capita,_​consumption_​per_​capita_​and_​price_​level_​indices). The major indications for CS are repeated caesarean section, dystocia, breech presentation, foetal conditions (such as macrosomia, prematurity, anomalies or abnormal lie), foetal distress, multiple pregnancies and maternal conditions (such as antepartum haemorrhage, diabetes and preeclampsia) [8]. However, most of the indications are relative and CS rates for various indications vary widely [8]. Previous population based studies from Australia, Canada and UK reported higher prevalence of CS performed due to repeated CS [9‐11], dystocia [11] and elective prelabor CS, especially for nulliparous women [12]. A few previous studies have demonstrated differences in CS rates between socioeconomic status (SES) groups within countries. Women with low SES or living in deprived areas were less likely to give birth by CS compared to women with high SES or living in affluent areas [13, 14], even in countries with publicly funded healthcare [15, 16], indicating that inequity may exist in some healthcare services. On the other hand, a large population based study from the Norway reported that women with the lowest level of education were more likely to give birth by CS [17].

In Finland, previous studies have reported SES disparities in amenable deaths [18] and invasive cardiac procedures [19, 20], showing that women with the highest SES have the lowest risk. Further, women with the highest SES were more likely to undergo in vitro fertilization in Finland [21‐23]. In Finland, practically all pregnant women give birth in public hospitals with free-access, and private delivery care services are not provided. The aim of the present study was to explore whether giving birth by planned and non-planned CS was associated with SES and other characteristics among singleton pregnancies during 2000–2010 in Finland.

In total, 19.8% (51,511 of 259,736) of the nulliparous women and 13.1% (47,271 of 360,727) of the multiparous women with singleton births gave birth by CS during 2000–2010 in Finland (Table 1). The total CS rate was relatively constant during the 11-year study period among both parity groups. Women who gave birth by CS were in general older, gave birth more frequently to a male infant with lower mean gestational age and were more likely to have high SES (upper or lower white collar worker) than women who gave birth vaginally, regardless of parity. As expected, giving birth by CS was associated with several reproductive risk factors during index pregnancy, such as induction, preeclampsia, gestational diabetes, diabetes mellitus, IVF, placental abruption, placenta previa and fear of childbirth, as well as prior history of pregnancy terminations and miscarriages among both parity groups. Nulliparous women with infants weighing less than 3000 grams or at least 4000 grams and multiparous women with infants weighing less than 3000 grams were more likely to undergo CS. Multiparous women were more likely to give birth by CS if they had a prior history of CS birth.

After adjustment for case-mix in logistic regression analysis, the prevalence of planned CS births in nulliparous women was 9% (adjusted odds ratio (aOR) 1.09, 95% confidence interval (CI) 1.03-1.11) higher in lower white collar workers, and the prevalence of non-planned CS birth was 7% (aOR 1.07, 95% CI 1.01-1.13) higher in blue collar workers compared to upper white collar workers (Table 2). In multiparous women, the prevalence of planned CS was 17% (aOR 1.17, 95% CI 1.11-1.24) higher in lower white collar workers and 16% (aOR 1.16, 95% CI 1.09-1.24) higher in blue collar workers compared to upper white collar workers (Table 2), whereas the prevalence of non-planned CS was 15% (aOR 1.15, 95% CI 1.07-1.23) higher in blue collar workers compared to upper white collar workers. Differences between other SES groups were non-significant regardless of parity and CS type.

Placenta previa was the strongest risk factor for planned CS and placental abruption was the strongest risk factor for non-planned CS, regardless of parity. Other delivery characteristics associated with planned CS birth were advanced maternal age (≥ 40 years), a birth weight of less than 3000 grams, a birth weight of 4000 grams or more, maternal diabetes mellitus, fear of childbirth and IVF, regardless of parity. Delivery characteristics associated with non-planned CS birth were advanced maternal age, a birth weight of less than 3000 grams, a birth weight of 4000 grams or more, preeclampsia, gestational diabetes, fear of childbirth, IVF and prior terminations, regardless of parity. Further, in nulliparous women, an increased prevalence of non-planned CS birth was associated with smoking and induction of labor. In multiparous women, prior CS birth was associated with an increased risk of both CS types.

After adjustment for case-mix, the prevalence of planned CS appeared to decrease by 40% in nulliparous women and by 55% in multiparous women from 2000–2003 to 2008–2010, whereas differences in non-planned CSs between the time periods were non-significant. The same logistic regression analyses were performed for both groups of women using multiple imputations for the missing data, but the results did not change (data not shown).

Table 3 presents crude and adjusted ORs of SES for CS birth (separately for planned and non-planned CSs) according to parity and different confounders. Delivery characteristics were added separately to Model 2 (adjusted for maternal age) to evaluate the contribution of each characteristic to the ORs of SES for CS birth. It appeared that maternal age made a major contribution and maternal smoking during pregnancy a moderate contribution to the prevalence of both CS types associated with SES. Further, the contribution made by the birth weight was minor. In nulliparous women, 21.4% of the differences in planned CS birth prevalence and 17.4% of the differences in non-planned CS birth prevalence between blue collar workers and upper white collar workers could be explained by smoking during pregnancy (percentage reduction in OR of SES-CS between Model 2 and Model 5 in Table 3). In multiparous women, 18.8% and 19.2% of the difference between blue collar workers and upper white collar workers in planned and non-planned CS births, respectively, could be explained by smoking during pregnancy.

We conclude that the mode of delivery is an important healthcare policy issue since the constantly rising prevalence of CS births, especially in medium- and high-income countries, does not seem to translate into better maternal and neonatal outcomes [2, 29]. In the present study, using the most recent population based data, we detected a decreasing prevalence of planned CS births among singleton pregnancies in Finland with good perinatal outcomes assessed based on several quality indicators [5]. However, we observed a higher prevalence of CS births among women with lower SES compared to the highest SES, which probably reflects the known social gradient in pregnancy complications, and consequently increased need for operative deliveries in women with social deprivation. Overall, the CS policy in Finland shows no inequity in healthcare, which is an important quality indictor in publicly funded services.