New research to be published in BJOG: An International Journal of Obstetrics and Gynaecology shows a link between the development of placenta praevia and placental abruption during the subsequent pregnancies of women who previously had a caesarean section.
Placental praevia is defined as the implantation of the placenta over or near the internal opening of the cervix. Placenta abruption is the premature separation of the placenta from the uterus. Both result in bleeding during the pregnancy, which could spell danger for mother and baby.
This study was undertaken to examine the risk of placenta praevia and placental abruption in singleton, second pregnancies after a caesarean delivery in the first pregnancy.
Data provided by the US National Centre for Health Statistics, Centres for Disease Control and Prevention was examined by a team of Canadian researchers. A total of 5, 146 742 pregnancies were analysed over 1995 - 2000. This is the largest population-based study of its kind to date.
Researchers found that women who previously delivered by caesarean section had a 47% increased risk of developing placenta praevia and a 40% increased risk of placental abruption in the following pregnancy.
The authors believe that caesarean sections cause scarring inside the womb which may affect placental attachment in future pregnancies. The ligation of the uterine vessels during caesarean sections could also damage the lining of the womb, resulting in the low implantation of the placenta in the next pregnancy.
Dr Qiuying Yang of the Ottawa Health Research Institute and University of Ottawa said, "Our paper, which is the largest study to date, shows an important association between caesarean sections and the subsequent pregnancy complications of placenta praevia and placental abruption."
"More than 1% of pregnancies with a prior Caesarean section had one of these events which had a 50% increase compared to women without previous Caesarean section. This has important implications on the management of these pregnancies. It also introduces new and important evidence in the debate on the risks of caesarean sections 'on demand'."
Professor Philip Steer, BJOG editor-in-chief, said "The caesarean section rate in the UK is one of the highest in the world. This isn't because, in some cases, women are 'too posh to push', but rather, complications occur during the pregnancy or birth which make normal delivery impossible."
"Women need to be informed of the possible risks that can happen throughout the pregnancy and it is important to have their scheduled ultrasound scans to detect if the baby is developing safely. Should a woman encounter unusual bleeding during her pregnancy, it is best if she sees the doctor immediately."