Study suggests demographic factors can predict risk of operative births in UK women
Independent maternal demographic factors such as social status, ethnicity and maternal age can predict the likelihood of operative births in the UK, according to a new study published today (20 March) in BJOG: An International Journal of Obstetrics and Gynaecology.
The study, conducted by researchers in the Department of Health Sciences at the University of York, explores which women are at an increased risk of an operative birth, including caesarean section (CS) or instrumental vaginal birth. It looks at data from the Millennium Cohort Study of babies born in the UK between 2000-2002 and includes 18,239 mother-infant pairs.
Rates of CS in the UK have increased since the 1980s, however, there has been no associated decrease in instrumental vaginal births. Operative births can lead to longer hospital stays and poorer psychological wellbeing, and represent a substantial financial cost to the NHS.
The researchers looked at four categories of mode of birth, including unassisted vaginal birth, instrumental vaginal birth, emergency CS and planned CS, and the impact of demographic factors such as age, ethnicity and socio-economic status, while controlling for a wide range of individual factors.
Findings showed that age played a significant role in determining mode of birth for all women, with operative birth rates rising with increasing maternal age. For example, 9.4% of first-time teenage mothers required an emergency CS compared with 30.3% of first-time mothers aged 35 or older.
Researchers found that some independent maternal factors differed when comparing primiparous (first-time mothers) to multiparous (have had one or more previous births) women.
Factors such as social status, ethnicity, and the mother’s age can predict the likelihood of caesarean section and other operative births in the UK, finds research published in BJOG: An International Journal of Obstetrics and Gynaecology.
These factors may explain the wide discrepancies in caesarean section rates across England, speculate the authors.
The researchers assessed data from 18,239 mother-infant pairs who were part of the Millennium Cohort Study of babies born in the UK between 2000-2002 to see which women run a greater risk of an operative birth, including caesarean section or instrumental vaginal birth.
C-section rates in the UK have increased since the 1980s, but there has been no associated decrease in instrumental vaginal births. Operative births can lead to longer hospital stays and poorer psychological wellbeing, and are costly for the NHS.
Socio-economic factors impacted women differently, with first-time mothers from lower occupational status households 1.5 times more likely to have an instrumental vaginal birth and over twice as likely to have a planned CS.
While for multiparous women, educational level was more predictive of mode of birth in women with A-level qualifications at a reduced risk of planned CS compared to women with degree-level qualifications.
Finally, mode of birth varied again in women according to migration status and ethnicity, with multiparous immigrant women who had lived in the UK for more than 5 years at an increased risk of emergency caesarean section compared to their UK or Ireland born counterparts.
Moreover, in comparison to white women, primiparous black women were less likely to have an instrumental vaginal birth and multiparous Pakistani and Bangladeshi women were less likely to have a planned or emergency CS.
The study used individual-level rather than area-level measures of socioeconomic status, and took account of a larger range of factors than any other study of this type has been able to before, she said.
“Further research is needed to establish to what extent sociodemographic differences in mode of birth are a reflection of the attitudes and behaviours of women, or health professionals, or whether they reflect deeper health differences among these women,” she concluded.
Holly Essex, Research Fellow at the Department of Health Sciences, University of York and lead author of the study, said:
“Our results show that socio-demographic characteristics of women in the UK can independently predict mode of birth.
“In this country there are significant variations in rates of CS between maternity units in different geographical areas and this research goes to show that it could be due in part to the characteristics of the population they serve.
Caesarean sections in the UK have been increasing year on year.
Although there are some quality and coverage issues with the data, the
graphs give a good sense of the changes in mode of birth over time in NHS hospitals. The total
caesarean section rate was 9% in 1980. However by 2008-09 almost 1 in 4 women (24.6%)
experienced a caesarean section.
The total instrumental vaginal birth rate has remained fairly constant over time, fluctuating between
around 9-12% of the total births. However, the use of vacuum extraction increased over the period,
whereas the use of forceps decreased, and in 2008-09 each represented around half of the total
instrumental rate, although the rate of vacuum extraction was slightly higher (6.6% vs. 5.5%). The
reasons for the fluctuations in instrument use over time are numerous, and each procedure is
recognised to have different advantages and disadvantages (Patel and Murphy, 2004, RCOG,
2005).
Rates of caesarean section by country
Rates of caesarean section have been shown to vary hugely between countries (Notzon, 2008);
however, not all countries have reliable data on national caesarean section rates, meaning that only
a small group of countries are frequently discussed with regard to comparative caesarean section
rates. Betràn and colleagues conducted a comparative study of global rates of caesarean section,
comparing over 120 countries (Betran et al., 2007). Caesarean section rates were obtained from
national health surveys, published vital statistics, searching electronic databases or government
websites, or through contacting health authorities directly. In addition to variation in the methods
needed to obtain national caesarean section rates, countries also varied in the way the rates were
reported (as a proportion of all births, or of all live births) and in the timing of the most recent data.
Data were collated by the authors in 2005, and the most reliable and recent data ranged from 1993-
2003 between countries. Data used for the United Kingdom in this study came from the National
Sentinel Caesarean Section Audit (NSCSA) from 2001, which gave an overall caesarean section
rate of 21.4%.
“We found that first-time mothers in lower social class bands were more likely to have an instrumental vaginal birth and a planned CS, which counters other studies showing women in more deprived areas are less likely to have planned CS births. Our study used individual-level rather than area-level measures of socio-economic status, and controlled for a larger range of factors than any other study of this type has been able to before.
“Further research is needed to establish to what extent socio-demographic differences in mode of birth are a reflection of the attitudes and behaviours of women, or health professionals, or whether they reflect deeper health differences among these women.”
Aris Papageorghiou, BJOG Scientific Editor, added:
“The large scale of this study provides strong support for the independent effect of maternal demographic factors on mode of birth in the UK population.
“It is important to have these figures and understand why there has been a growing rate of operative births over the past few decades.
“Women should be aware of all modes of birth available to them and discuss options and any concerns with a healthcare professional.”
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Caitlin Walsh
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020-777-26300
Wiley