Assessment of risk for the development of pre-eclampsia by maternal characteristics and uterine artery Doppler.

OBJECTIVE

To develop a method for the estimation of patient-specific risk for the development of pre-eclampsia by combining maternal history and uterine artery Doppler.

DESIGN

Prospective multicentre observational study.

SETTING

Antenatal clinics in seven hospitals in the UK and three overseas centres.

POPULATION

Unselected women with singleton pregnancies attending for routine antenatal care.

METHODS

Doppler studies of the uterine arteries were performed using colour flow mapping and pulsed wave Doppler at 23 weeks of gestation. The mean pulsatility index (PI) of the two uterine arteries was calculated. Doppler and maternal history variables were combined to develop a model for risk assessment. The incidence of pre-eclampsia was used to derive the prior risk for this complication. The posterior risk was derived by multiplying the prior odds with likelihood ratios (LRs) derived from independent risk factors identified from the maternal history, and the LR estimated from the heights of the frequency distributions of mean PI in affected and unaffected pregnancies.

MAIN OUTCOME MEASURE

Pre-eclampsia.

RESULTS

There were 17,480 women recruited to the study, in which 17,319 (99.1%) of these Doppler examination of both uterine arteries were completed, and outcome data were available in 16,806 (97.0%). Pre-eclampsia occurred in 369 (2.20%) cases. Significant independent prediction of pre-eclampsia was provided by mean PI, ethnic origin, body mass index (BMI), parity, cigarette smoking, history of hypertension and family or personal history of pre-eclampsia. Models were derived allowing calculation of patient-specific risk for development of pre-eclampsia. For a false-positive rate of 25%, the detection rate of pre-eclampsia by screening using maternal history was 45.3%, with uterine artery Doppler it was 63.1% and with combined assessment it was 67.5%.

CONCLUSIONS

Combining risk factors in the mother's history with Doppler of the uterine arteries allows calculation of patient-specific risk for the development of pre-eclampsia.