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The rate of caesarean section

Back ground

From the last few decades the rate of caesarean section is continuing to rise in many regions of the world, especially in industrial countries. Rates of c -sections have been increased in Norway as in the rest of the western world since 1970. Although C-section is a safer alternative to a difficult vaginal delivery where there is a clear medical explanation for its use, there is still possibility of long term health risks to the mother and child due to its unnecessary use (MacDorman, et al., (2008). Maternal complications due to caesarean section include, complications due to anaesthesia and surgery, and longer term reproductive morbidity and mortality in following pregnancies. Babies born by caesarean section are more prone to have respiratory distress, less breast-feeding and probably more atopic diseases (Tollanes, (2009); Van den Berg A, (2001) and MacDorman, et al., 2006.Ramachandrappa, 2008.

By taking into account the economic aspects of the delivery method, it has been observed that caesarean deliveries are more costly than vaginal deliveries. According to an audit commission report published in 2002 in the UK, a caesarean delivery costs hospitals an average of £1,701 as compared to a vaginal delivery which costs an average of £749. Therefore a one percent rise in CS rates costs the NHS an extra £5million per year (post note 2002, p.).

In addition, women who have a caesarean section are more likely to stay longer in the hospital and sometimes have to be re-admitted in the hospitals due to wound infections and other complications. It may also be important to think about long term health care costs due to the services used by women themselves and their infants following a caesarean birth (Wendy Sword, et al., 2009). In consideration of that first caesarean sections almost ensure that following pregnancies outcome will be Caesarean deliveries. It can be a financial burden for society and the national health system (Sword, et al., 2009).

World- wide high rates of caesarean deliveries are a matter of concern to international public health due to its consequences on maternal and child health and the associated socio-economic effects on society.

Literature review shows, high rates of caesarean delivers among all mothers irrespective of age, ethnicity, gestational age and medical status (Menacker, et al., (2006) and MacDorman, et al., (2008). None the less concerns have been raised over the high caesarean birth rates that go beyond the World Health Organization's (WHO) suggested rate of 15% and its potential risks to the maternal and prenatal health (Wendy Sword, et al; 2009).

In order to stop this progressive rise in rate of operative deliveries, a detailed analysis of the factors contributing to this increase is required. Many epidemiological studies have been conducted in various countries to determine the factors responsible for the global rise in Caesarean sections. Data analysis from different studies found a number of medical and non-medical factors that are responsible for the increase of caesarean deliveries both in developed and developing countries. Medical factors accountable are raise in maternal age, high body mass index (BMI) and changes in medical practice as explained by Tollanes (2009). Tollanes (2009) identified maternal preferences; improper maternity care and fear of legal action among obstetricians are major non medical reason for high prevalence of caesarean sections.

However, monitoring the overall rate may not be helpful in reducing unnecessary caesarean sections. It may be more useful to spot and aim at subgroups of women in whom unjustified caesarean sections could be avoided. To categorize subgroups of women who could be observed for possible risk of caesarean deliveries, a number of studies have been conducted in many countries. An analytical study was carried out in Latin America by, World Health Organization (WHO, 2004-2005) (Betran, et al., 2009). In this analysis two subgroups of mothers were identified to contribute high rates of operative deliveries that need to be monitored more closely. These subgroups include women with a single full term cephalic pregnancy: (a) with a history of previous c-section and; (b) those mothers who had c-deliveries after induction of labour or who had elective c-sections (Villar, et al., 2006).

Numerous studies have focused on familial inheritance of medical factors responsible for complications of pregnancy and its outcomes (Rolv T, 2007). A vigilant study of non- medical risk factors may allow us to identify reasons for the increasing rates of unnecessary Caesarean deliveries which are amenable to change. In order to evaluate these non- medical risk factors and their familial inheritance within the generations and across the generations quite a few studies have been conducted (Vernal, et al., 1996 and berg-Lekas, et al., 1997).

Study design

This study aimed to identify non medical risk factors for elective caesarean sections and their biological inheritance within families. Using data from Norway is valuable if an understanding is to be developed of the increasing operative delivery rates, specifically within this country but potentially in other contexts as well.

In this design a population-based data from the Medical Birth Registry of Norway (MBRN) was used and a retrospective- cohort of singleton live borne full term pregnancies was established with the help of national identification number. A cohort of 440236 grandmother-parent units and 275001 same sex full siblings units were constructed from singleton birth registered in the MBRN during 1967-2005. Out of 440236 grandmothers -parent units, 261156 were being identified with a female newborn and 179080 with a male new born, who became mother and father later in life. For the same sex full sibling unit 153085 pairs of full sisters and 121916 pairs of full brothers out of 275001 with their first birth were compared. In case of grandmother -parent units only the first birth of each mother and father was observed but mothers and fathers themselves were allowed to be of any birth order. To investigate the familial inheritance to non- medical factors, units with high risk factors for caesarean section were ruled out and low risk subgroups of grandmothers -parents units and full sibling units of sisters and brothers were constructed. Log - binominal regression models were used for statistical analysis in this study to measure the relative risks. In case of grandmother- parents units the exposure was grandmother delivering parents by caesarean and outcome was caesarean delivery for parents' first child. While in case of full siblings unit the exposure was weather older siblings first baby was born by caesarean delivery and outcome was measured by caesarean delivery in younger siblings' first child.

In this study there has been a clear increase in primary caesarean delivery without a medical or obstetrical indication. While confounding has been minimized as a result of the full adjustment of all aetiological factors at every stage of analysis, there may nevertheless be residual confounding.

Present work involved two separate analyses. First analysis compared mode of birth of first child in all mothers and fathers borne by c- deliveries to the all mothers and fathers borne by vaginal deliveries in both high risk and low risk parents. Results of this study showed mothers borne by caesarean sections due to complications of pregnancy and labour had 55% higher risk of caesarean deliveries than mothers borne by vaginal deliveries. A 95% confidence interval (1.48-1.62) seems to be quite significant and demonstrated strong statistical evidence of associations with the relevant outcome.

In case of mothers borne by c-section after a low risk pregnancy results showed twice the risk of giving birth by caesarean section. A wider gap in confidence interval minimizes the value of relative outcomes and its cooperation in wider population.

Strengths of the study

One of the main strength of the study is the provision of a large sample, which means that there is satisfactory potential to detect small but clinically vital associations. Another advantage of this study is use of a cohort design as compared to a series of cross-sectional studies that would need to take on new members for each study. Cohort study is quicker and cheaper as less technical staff is required to collect data. There is no need to follow individuals over time because all the information is already available so there is less chance of loss of contact and miss valuable information.

In these analyses the exposure and outcome measure is likely to be accurate since the midwife and medical staff involved in the delivery is responsible for recording this information data immediately after the birth.

More assurance can be found in the accuracy of the collected data because participants were not required to recall events for long periods of time. These models are simple in design but allow the exploration of the risk factors which may affect the whole community. These are called incident studies.

Limitations of the study

Although this analysis is distinctive by studying a nationwide data of pregnant women and their relative outcomes, it has several limitations. First, the accuracy of the collected data is difficult to assess for all factors. It is more likely, that clinical practice may have altered or new factors may have emerged, that influence mode of delivery. Several characteristics of individual women (such as parity, maternal age, and weight gain during pregnancy) have been quoted in the literature as being associated with Caesarean section. Joseph, et al., (2003) investigated that changes in maternal characteristics and obstetrical practice may contribute to recent increase in c- section prevalence. If these factors can be identified it may indicate key areas that could be targeted to control Caesarean section rates. However, the variables identified in these models are equally applicable to current clinical practice.

Data recorded over a long period of time may also be liable to changes in definitions and coding systems.

Second the quality and completeness of recorded data is crucial for a cohort study design. Especially in a retrospective cohort study the researcher goes back in time to define exposed and unexposed groups and re-evaluate medical records to follow participants for outcomes. As routine data systems are planned to serve as surveillance, and not a research study, some data may be missing or inaccurate.

Another disadvantage of routine data may not be able to provide all the necessary information on other important risk factors under investigation which, if unaccounted for may lead to bias.

Northam and Knapp,(2006)

Comparison with other studies

This research adds to previous work on trends and an aetiological factor associated with C- section and on the whole has similar findings. In all analyses, maternal and foetal risk factors (such as, maternal age, placenta previa, gestational diabetes, eclampsia and preeclampsia, macrosomia and many more) were found to be independently associated with increased rates of Caesarean section. These have the possibility of maternal and foetal inheritance, which is in keeping with other studies. (Lie RT, 2007; Plunkett J, 2008; Onsrud L; Onsrud M, 1996).

There are several socio-cultural and environmental factors acknowledged in the literature related with C- section has not been confirmed by this research. For instance, many studies have found social class, nature of employment, and educational attainment, to be associated with Caesarean section, none of which were observed to have independent associations with mode of delivery in these analyses. This view has been supported by the work of Tollan, et al., (2007), who described the association between caesarean sections and maternal social background. Results of the study showed that level of education is inversely related to the risk of caesarean deliveries. Similar findings have been observed by Torun, et al., (2006) regarding socio-economic status of women and related risks to the pregnancy outcomes. Giulia, et al., (2008) explored the role of social class and effect of educational degree on caesarean deliveries in Italy. This research also concluded mothers from lower social class and with lower educational achievement are more likely to deliver by caesarean sections than mothers with higher educational levels.

On the other hand some studies found a direct association between high caesarean section rates and high socio economic position. Found C -deliveries are more common among those low risk nulliparous mothers, who are well educated, belong to high socio economic class and have better excess to antenatal care. In UK, NHS obstetrician identified that 1.5% of all C -sections are accrediting to maternal lifestyle and choices in the absence of any clear medical indication. This has been suggested due to the trends in several celebrity women to give birth by elective c-section as these mothers are" too posh to push' (Postnote, 2002, p.2). Lei, et al., (2003) stated women's medical insurance, social status and preferences, are suggestive for a considerable increase in rates of elective Caesarean deliveries in China.

The continuously high rates of elective Caesarean section (ECS) performed at a woman's request in the absence of a recognized obstetrical indication, is becoming increasingly common in the most developed countries. (Gamble and Creedy, 2000). McCourt, et al., (2007) reviewed published literature concerning maternal request for elective c-section and observed a very small number of women requesting for caesarean deliveries. The researcher evident a range of non-medical reasons, such as the woman's fear of child birth, her desire to give birth on a lucky date or time, or her understanding that an operative delivery would save the baby's brain from trauma or harm . Weaver, et al., (2007) observed similar association between psychosocial factors and maternal request for caesarean deliveries in UK.

However, these studies contain no clear information whether these caesareans were the result of maternal request or because of physician recommendation. More research is needed to determine the factors associated with maternal preferences, obstetrician practice pattern, and institutional culture, personal and social reasons that affect the decision to have a caesarean delivery.

In the case of ethnicity and race, the study area has no knowledge of ethnic minorities and this may have underpowered this part of the analyses. Evaluation from different studies showed linkage between cultural and racial subgroups and maternal and neonatal outcomes. This view has been supported in the work of Johnson, et al., (2005). Vangen, et al., (2000) found a substantial variation in c-section rates among different ethnic communities in Norway. Similar results have been described by Robertson, et al., (2005) regarding risk of non vaginal deliveries and mother's country of birth. This could be explained by variations in provision and use of health services by people of different socio cultural origin as described by Berkin (1990). NY, et al., (2007) observed equivalent findings in the use of health services by people of different ethnic background in Sweden.

For the other factors, this research has minimized confounding and suggests that they are not independently associated with mode of delivery in the study population. Maternal height and weight are one of the important risk factors not verified in this analysis. McEvoy and Visscher, (2009) both described eighty percent of human growth is under genetic control suggestive of resemblances and variations in height and weight between relatives.

Many studies summarise that both genetic and environmental factors regulate the human height and weight in different populations (Letter, et al., 2008). Similarly strong genetic association for body mass index and human stature was found by Sammalisto, et al., (2009). Letter (2009) highlighted the involvement of genes in difference in adult height and stature. Work of Hirscohhorn and Letter, (2009) also provides valuable information regarding biological inheritance of human growth and genetic variations in height within a population.

Several studies conducted in developed countries have found that pre- pregnancy obesity, a growing societal trend, is associated with an increased likelihood of maternal and foetal complications responsible for caesarean sections. According to these studies overweight mothers are more likely to have pre-eclampsia, gestational hypertension, foetal congenital anomalies, macrosomia, and gestational diabetes, and cervical dystocia, induction of labour and caesarean deliveries. Similar trends are described by Bhattacharya, et al., (2007) and Crane, et al., (2009). This view is also supported by Satpathy, et al., (2008) who studied the adverse effect of obesity related to complications during pregnancy and labour. Poobalan , et al .,( 2009) found that risk of caesarean deliveries could be more than double in overweight women as compared to mothers with normal BMI. Young and Woodmansee, (2002) found increased BMI and weight gain are more likely associated with CPD and failure to progress in nulliparous women. Mollar, Lindmark (1997) evaluated the relationship of maternal height to obstructed labour and caesarean deliveries. Kara, et al., (2005) stated that short maternal stature is associated with an increased incidence of obstructed labour due to cephalopelvic disproportion (CPD).

CPD is still a major obstetric risk factor for maternal and infant mortality in many parts of the world where operative deliveries are not readily available. According to the World Health Organisation (WHO) about 529,000 maternal deaths occurs throughout the world per year and obstructed labour is one of the major obstetrical factor responsible for these maternal mortalities (WHO, 2005). Hoefmeyr (2004) identified an eight percent of maternal mortalities are due to obstructed labour. To investigate the risk factors for C-Section due to CPD a study was conducted by Khunpradit, et al., (2005) .Who observed maternal height less than 150 cm and weight more than 15 kg is significantly related to increased risk of CPD. Scott, et al., (1998) found short statured women are more likely to have risk of C-sections for CPD than the taller mothers.

Variations in maternal pelvic sizes and shapes and fetal sizes could be explained by biological inheritance in different populations .This is described by Vernal, et al., (1996) that mothers who are being borne by caesarean deliveries themselves due to cephalopelvic disproportion (CPD) are at a greater risk to have CPD later in their lives. Berg-Lekas, et al., (1998) observed chances of operative deliveries between generations and within generations by comparing mother-daughter units, sister units and twin sister units and found a significant odd ratio between them. These finding show familial inheritance to CPD, possibly through genetic effects on mothers' pelvis dimension or fetal weight. Lunde, et al., (2007) explained maternal and fetal genetic factors responsible for variation in head circumference, birth height and weight within families. Beaty, (2007) Heritability of small size maternal pelvises and large size foetus could be another explanation of familial predisposition of operative deliveries.

Finally, this data did not have any information about institutional characteristics, as type of hospital, and type of professionals attending the births. J, et al., (2009) studied the relationship between social class and type of maternity services used by urban resident in southern Europe and found high rates of caesarean sections among high social class delivering in private hospitals. Potter, et al., (2009)(2001) stated that in Brazil, higher rates of c- section were among women delivered in private maternity units as compared to public hospitals . Almeida, et al., (2009) observed similar findings and suggested that most of the caesareans were scheduled according to women's or physicians convenience and showed no clear medical justification for the procedure.

Conclusions

Despite the study design and methods this research reflect that there are increasing c-section rates in low risk population. These analyses have verified various important prenatal risk factors for elective caesarean deliveries and highlighted their familial association. In addition, these findings can be useful for early identification and counselling of high risk mothers regarding their preferences to different delivery methods. These findings can be incorporated into public and private maternity care sectors, medical directors, and administrators in early risk assessment and strategic management.

More studies are required to widen the scope of possible biological inheritance of non medical risk factors and their correlation with socio cultural background. Further research is needed regarding maternal requests and preferences about child birth including information about choices and knowledge relative to the use of intervention and its long term outcomes. An appropriate methodology should be used to observe maternal satisfaction with labour and delivery care and interactions between patients and care providers. A comprehensive study of cultural trends within obstetrical practice and methods used for reporting caesarean section rates in the country or hospital which have changed over time, should be conducted. Studies relating to funding arrangements and policy guidelines of the hospitals, medical organizations and health departments should be observed. In summary, greater attention needs to be given to the socio-economic, cultural, medical and political perspective of maternity care.

In conclusion, the information in this study is significant for those who intend to reduce Caesarean section rates, as it allows early detection of women at a high risk for surgical intervention. Finally, these finding can aid in the development and implementation of better strategies to prevent unnecessary c- sections and to reduce the cost of care in health system with readjustment of resource allocation according to population requirements.

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