Management of pregnancies after combined screening for pre-eclampsia at 19-24 weeks' gestation.

OBJECTIVE

To estimate the patient-specific risk of pre-eclampsia (PE) at 19-24 weeks' gestation by maternal factors and combinations of mean arterial pressure (MAP), uterine artery pulsatility index (UtA-PI), serum placental growth factor (PlGF) and serum soluble fms-like tyrosine kinase-1 (sFlt-1). On the basis of the risk of PE, the women would be stratified into high-, intermediate- and low-risk management groups. The high-risk group would require close monitoring for high blood pressure and proteinuria at 24-31 weeks. The intermediate-risk group, together with the undelivered pregnancies from the high-risk group, would have reassessment of risk for PE at 32 weeks to identify those who would require close monitoring for high blood pressure and proteinuria at 32-35 weeks. All pregnancies would have reassessment of risk for PE at 36 weeks to define the plan for further monitoring and delivery.

METHODS

This was a prospective observational study of women attending for an ultrasound scan at 19-24 weeks as part of routine pregnancy care. Patient-specific risks of delivery with PE at < 32 and at < 36 weeks' gestation were calculated using the competing-risks model to combine the prior distribution of gestational age at delivery with PE, obtained from maternal characteristics and medical history, with multiples of the median (MoM) values of MAP, UtA-PI, PlGF and sFlt-1. Different risk cut-offs were used to vary the proportion of the population stratified into high-, intermediate- and low-risk groups, and the performance of screening for delivery with PE at < 32 weeks' gestation and at 32 + 0 to 35 + 6 weeks was estimated.

RESULTS

The study population of 16 254 singleton pregnancies included 467 (2.9%) that subsequently developed PE (23 delivered at < 32 weeks, 58 delivered at 32 + 0 to 35 + 6 weeks and 386 delivered at ≥ 36 weeks). Using a risk of > 1 in 25 for PE at < 32 weeks' gestation and risk of > 1 in 150 for PE at < 36 weeks, the proportion of the population stratified into the high-risk group was about 1% of the total, and the proportion of cases of PE at < 32 weeks' gestation contained within this high-risk group varied from about 35% with screening by maternal factors and MAP, to 78% with maternal factors, MAP and UtA-PI, and up to 100% with maternal factors, MAP, UtA-PI and PlGF, with or without sFlt-1. Similarly, the proportion of the population requiring reassessment of risk at 32 weeks' gestation and the proportion of cases of PE at 32 + 0 to 35 + 6 weeks contained within this population varied, respectively, from about 18% and 79% with screening by maternal factors and MAP, to 10% and 90% with maternal factors, MAP, UtA-PI and PlGF, with or without sFlt-1.

CONCLUSION

In the new pyramid of pregnancy care, assessment of risk for PE at 19-24 weeks' gestation can stratify the population into those requiring intensive monitoring at 24-31 weeks and those in need of reassessment at 32 weeks. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.