Limiting the caesarean section rate in low risk pregnancies is key to lowering the trend of increased abdominal deliveries: an observational study

Relevant and available characteristics of patients, their pregnancy and delivery are depicted in table 2. Although the percentage of multiple pregnancies is comparable in both study years, the incidence of malpresentations is higher in 2008 (5.9% versus 4.9% in 2000). Mean gestational age at birth remained stable at 38.7 weeks in both years. Whereas no differences in mean birth weight are found throughout the years (3294 grams in 2000, 3309 grams in 2008), the percentage of vaginal deliveries (including vaginal breech deliveries) as well as vacuum extractions and the use of the forceps have all decreased in the study period in favor of Caesarean sections, with equal augmentations in primary CS and secondary CS. Even though the permillages of both fetal death and neonatal death are lower in 2008, no significant difference was found between both years. A lower incidence of multiple pregnancies is noticeable in 2004. This is due to the introduction of a government measure in 2003 in order to stimulate the use of single embryo transfer in assisted reproduction [8].

Tables 3 en 4 shows the 10-group classification according to Robson. We compared the 10-groups for the years 2000 with those of the year 2008 in table 3. In order to picture the trend over those years, the classification of the year 2004 is provided in table 4. Columns 3 and 7 show the number of CS for the total number of births in each group for the years 2000 and 2008 respectively. The relative value of groups in total births (columns 4 and 8) is calculated by dividing the number of births in each group by the total obstetric population for the given year and expresses the 'importance' or 'weight' of each group in the total population. The next (fifth and ninth) column shows the CS rate in each group and represents the fractions as depicted in columns 3 and 7. The 'contribution per group' columns (columns 6 and 10) show the percentage contribution by each group to the overall birth rate (number of CS/total obstetric population for the given year). This classification allows assessing which groups contribute more to the overall section rate.

Our results show an increase of the CS rate in all groups, except in the group of multiparous women with a term single cephalic pregnancy (group 3) which remains more or less stable. The most notable rise is detected in women with previous sections (group 5) and in nulliparous term women in spontaneous labor of a single cephalic (group 1). In multiple pregnancies (group 8), there is an obvious lower threshold in 2008 to perform a CS compared with the year 2000. In 2000, groups 2, 5 and 6 contribute most to the CS- rate; in 2008 the dominance of group 5 (repeat CS) is notable, the group of nulliparous women with induction or elective CS is the second - most important and the third place is shared by group 1 (lowest - risk group) and group 6. As a consequence the group of term nulliparous women with a singleton cephalic in spontaneous labor contribute as much to the CS - rate as the group with nulliparous breech presentations. Conversely, there is no 100% CS - rate in group 9 (abnormal lies), this can be explained by the high preterm birth rate in this group. Groups 1 to 4 represent uncomplicated pregnancies; in 2000 this group represented 80.9% of total deliveries, while in 2008 there was a slight increase (88.4%). This implicates a increase in the percentage of low - risk patients. When the magnitude of rise in contributions per group is calculated, a 41% rise is detectable in both groups 1 and 5.

Details of mode of delivery in the low-risk populations are depicted in Figure 1 and 2 (for 2004). Low-risk deliveries are defined as deliveries in primipare women, who deliver from a term live born singleton without malformations in vertex presentation with a birth weight between 3000 and 4000 grams. Figure 1 shows an important reduction of instrumental deliveries in the advantage of natural vaginal deliveries, but more notably in favor of the non - elective CS - rate.

In table 5 CS - rates according to different maternal age groups are illustrated. There is a relative increase of the CS - rate in all age groups, but no statistical significant rise in risk - groups (teenage mothers or women of advanced age). In the age group 20-34 years, a significant increase of the CS - rate is found.

The trend of inductions of delivery is depicted in table 6. In 2000, 33% of all deliveries were induced; in 2008 this proportion decreased to 27.7%. However, the percentage of CS after induction increased from 13.2 to 17.9%. Particularly in gestational weeks 39, 40 and 41, there was an increase in failure of induction.

Differences in CS rates between the hospital with the lowest rate of abdominal delivery (hospital A) and the hospital with the highest rate (hospital B) are depicted in table 7. In general, there is a three times higher Caesarean section rate in the hospital with the highest rate (which is not a university hospital) when compared to the hospital with the lowest rate (26.3% versus 9.1%); looking at the low-risk pregnancies only (groups 1 and 2), a five times higher CS rate is found (24.6% versus 4.6%). Because of the historically low CS rate in hospital A, the relative value of group 5 is considerably lower in this hospital when compared with hospital B (1.6% versus 9.1%). The differences in CS percentage in the breech - presentation groups (6 and 7) are notable as well.

While there is a balanced contribution of the first 5 groups (4.9%) and the last 5 groups (4.2%) in hospital A, the balance in hospital B gravitates towards the lowest - risk groups (18.9% versus 7.2%). In hospital A, there was a perinatal death rate of 3.63 ‰, compared to 4.97 ‰ in hospital B.

Fetal well-being is one of the main reasons to proceed to Caesarean section. Reasons for perinatal death are registered accurately in our database as this parameter is one of the most important for perinatal outcomes. Table 8 shows a slight increase in the total absolute number of perinatal deaths in 2008, but a non - significant relative decrease (6.2‰ versus 6.7‰ in 2000). In general, it can be said that the 3% rise in CS in the studied period did not result in a substantial increase of perinatal survival, although there were 8 more perinatal deaths due to asphyxia in 2000 when compared with 2008 (7.7% in 2000 versus 5.6% in 2008). The most remarkable changes in perinatal mortality are found in the categories 'intra - uterine death of a normal fetus' 111 infants in 2008 versus 88 in 2000) and 'low birth weight' (52 infants in 2008 versus 39 in 2000).

Changing trends in mode of delivery may be a reflection of associated changes in the patient population. Assessment of our patient populations demonstrates increasing proportions of women of advanced age and elevated use of assisted reproduction. However, multiple regression analysis did not indicate these parameters to have a large impact on our results.

Our dataset did not allow to adjust for CS due to maternal request or the impact of maternal obesity, which is a shortcoming.

Our comparison between the Flemish hospital with the lowest and highest abdominal deliveries shows that hospital policy has an essential impact on CS rate. A lot of studies consider a Caesarean section rate of 15% as the most optimal. This cut-off is based on the prevalence of maternal complications which could be effectively addressed by advanced levels of care including (but not limited to) Caesarean section [3]. This rate is recommended to ensure maternal safety, so maybe there should be space for discussion and reconsideration whether the 15% rate is not too narrow to guarantee both maternal and fetal safety. According to Robson (2001), the question is not whether CS rates are too high or too low, but rather whether abdominal deliveries are performed when appropriate or not in a given circumstance. For Robson, a CS is convenient when the information is available to explain and justify it [7]. Brennan et al. [9] compared Caesarean delivery rates between nine institution of different countries. Their results showed significant variability in overall CS rates across the centers. These variations were largely explained by variations in spontaneously laboring term nulliparae.

It would be of interest to account for obstetrician characteristics (age, experience in vaginal breech deliveries, etc.) in future studies.

Complications for the following pregnancy include a higher incidence of placenta previa and accrete (of which the risk is greater than 60% in women who have had four or more abdominal deliveries). On the shorter term, there are more thromboembolic problems and infections after CS [10]. Mother - child acquaintance is postponed after CS, in that standard admission to neonatal care is more common [3], which introduces to health - economical considerations. The health economical aspect of the abdominal delivery has escaped extended research so far, notwithstanding CS to be the operation most often performed in Western countries [11]. With longer hospital stays for both mother and child plus the additional complications, it may be assumed that abdominal delivery is the less economical option.