Background Pre-eclampsia affects 2–8% of pregnancies. It is important to determine baseline risk of pre-eclampsia to offer preventative interventions to women most likely to benefit. National Institute for Health and Clinical Excellence guidelines recommend aspirin for women at high risk of pre-eclampsia and state that aspirin may be offered to women with ≥2 moderate risk factors. However, risk of pre-eclampsia in women with ≥2 moderate risk factors is unclear.
Objectives To determine the risk of pre-eclampsia in women with two moderate risk factors, one of which is primiparity, and the other is either age ≥40 years, body mass index (BMI) >35, or multiple pregnancy.
Methods The electronic Meditech system at the Liverpool Women's Hospital was used to retrieve data on women delivered at the hospital from 2005–2009. The incidence of pre-eclampsia was calculated for each combination of moderate risk factors. We controlled for high risk and other moderate risk factors by excluding those women from analyses.
Results 40 363 women delivered at LWH during 2005–2009. The incidence of pre-eclampsia in primiparous women aged ≥40 years was 6% (33/550, 95% CI 4.6% to 8.7%), in primiparous women with BMI >35 kg/m2 was 7.2% (55/764, 95% CI 5.5% to 9.3%) and in primiparous women with multiple pregnancy was 10% (34/339, 95% CI 7.1% to 13.7%).
Conclusions For primiparity in combination with age ≥40 years, BMI >35, or multiple pregnancy, the incidence of pre-eclampsia ranges from 6% to 10%. The role of aspirin for these indications needs further evaluation.