Risk Factors For Uterine Rupture And The Neonatal Consequences

Main Category: Pregnancy / Obstetrics
Also Included In: Women's Health / Gynecology;  Pediatrics / Children's Health
Article Date: 04 Oct 2007 - 4:00 PST

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New research to be published in BJOG: An International Journal of Obstetrics and Gynaecology calls for prudent management of women with a history of caesarean delivery after finding that the risk of uterine rupture during subsequent birth is significantly increased following a previous caesarean. The study also found that uterine rupture is influenced by induction of labour, birthweight, gestational age, and maternal characteristics.

The study from the Department of Epidemiology at Emory University, Atlanta, and the Department of Medical Epidemiology and Biostatistics at the Karolinska Institute in Stockholm included 300 200 women in Sweden with live single births in second pregnancy. The risk of uterine rupture was considered against factors such as mode of first delivery, interpregnancy interval, onset of second delivery, vaginal instrumental second delivery, birthweight, gestational age, and maternal characteristics including maternal age at delivery, maternal education, smoking habits, BMI, and height.

Of the women studied, 24 876 were attempting vaginal delivery after a previous caesarean section. The study found that 24.7% of the women who had a previous caesarean birth required an emergency caesarean compared to 2.2% of the women whose primary birth was vaginal.

The overall rate of uterine rupture among women with an attempted vaginal birth in their second delivery was 0.91 per 1000. The rate of uterine rupture among women who attempted vaginal birth after a previous caesarean was 9.00 per 1000 compared with 0.18 per 1000 for those without a history of caesarean delivery.

Women whose labours were induced were at twice the risk of uterine rupture than those whose onset of labour was spontaneous, both among women with and without a previous caesarean. In line with previous studies the researchers suggest that induction agents such as prostaglandins and oxytocin, which are used to increase uterine contractions, can result in hyperstimulation of the uterus and can weaken previous caesarean scars making them more susceptible to rupture.

Gestational age also contributed to increased risk of uterine rupture, regardless of caesarean history or onset of labour. The study found that those who gave birth at ≥42 weeks had a higher risk than those with a gestational age of 37-41 weeks. High birth weight also played a significant role, women with infants that weighed ≥4000g at birth were twice as likely to experience uterine rupture than those with infants weighing ≤4000g.

Researchers also looked at uterine rupture in the second delivery and neonatal mortality and found a dramatic 60-fold increase in risk. Among the 274 women that experienced uterine rupture there were 14 neonatal deaths (51.09 per 1000). This compared to a rate of 1.4 per 1000 for women without uterine rupture.

Miss Melissa Kaczmarczyk, Department of Epidemiology, Emory University, School of Public Health, said "Our study is one of the largest population-based cohort studies to examine the risk factors for uterine rupture in all women regardless of history of caesarean delivery."

"We found that previous caesarean, induction of labour, and high maternal age to significantly increase the risk of uterine rupture. This is of particular concern due to a rise in the presence of these factors within the pregnant population.

"Patient counselling and prudent management of labour among patients considered to be at higher risk is needed to prevent this catastrophic event and associated neonatal morbidity and mortality."

Professor Philip Steer, BJOG editor-in-chief, said "The rate of caesarean deliveries continues to increase in the developed world which means that a growing percentage of women will experience birth following a previous caesarean section."

"Although uterine rupture is a relatively rare occurrence, the consequences can be devastating. The link between a prior caesarean section and uterine rupture during subsequent delivery warrants very careful management of pregnancy and labour so that early signs of difficulty can be speedily detected and ensuring that women are fully informed of their options regarding mode of delivery." BJOG: An International Journal of Obstetrics and Gynaecology is owned by the Royal College of Obstetricians and Gynaecologists (RCOG) but is editorially independent and published monthly by Blackwell Publishing. The journal features original, peer-reviewed, high-quality medical research in all areas of obstetrics and gynaecology worldwide. Please quote 'BJOG' or 'BJOG: An International Journal of Obstetrics and Gynaecology' when referring to the journal.

References

Kaczmarczyk M, Spare´n P, Terry P, Cnattingius S. Risk factors for uterine rupture and neonatal consequences of uterine rupture: a population-based study of successive pregnancies in Sweden. BJOG 2007;114:1208-1214.

Royal College of Obstetricians and Gynaecologists