The effect of maternal factors and biomarkers is to modify the mean of the distribution of gestational age at delivery with PE so that, in pregnancies at low-risk of PE, the gestational age distribution is shifted to the right with the implication that in most pregnancies delivery will actually occur before development of PE. Our approach assumes that, if the pregnancy was to continue indefinitely, all women would develop PE and whether they do so or not before a specified gestational age depends on competition between delivery before or after development of PE. We have proposed that the best approach to screening for PE is to use Bayes' theorem to combine the a-priori risk from maternal characteristics and medical history with the measurement of biomarkers 8- 10.

Maternal serum alpha-fetoprotein (AFP) levels during the first and or second trimester of pregnancy are altered in pregnancies with aneuploidy, neural tube defects and adverse pregnancy outcome, including fetal death, pre-eclampsia (PE), fetal growth restriction and preterm birth 1- 7. Measurement of serum AFP at 11вЂ“13 and 19вЂ“24 weeks' gestation improves the prediction of preterm PE provided by maternal factors alone. The DRs, at 10% FPR, of combined screening at 11вЂ“13 weeks for PE delivering < 32 and at 32 + 0 to 36 + 6 weeks were 54% and 45%, respectively, and these improved to 72% and 53% with screening at 19вЂ“24 weeks. The performance of screening for preterm PE was better at 19вЂ“24 weeks than at 11вЂ“13 weeks and the detection rate (DR) for a given false-positive rate (FPR) was higher for PE delivering < 32 weeks than for PE delivering at 32 + 0 to 36 + 6 weeks. Combined screening with maternal factors and serum AFP improved the prediction provided by maternal factors alone for PE delivering < 37 weeks, but not for PE delivering в‰Ґ 37 weeks. In pregnancies that developed PE, serum AFP multiples of the median (MoM) was increased at 11вЂ“13 and 19вЂ“24 weeks' gestation, but not at 30вЂ“34 weeks, and the values were inversely related to gestational age at delivery. The performance of screening for PE requiring delivery < 32, at 32 + 0 to 36 + 6, < 37 and в‰Ґ 37 weeks' gestation was estimated. Bayes' theorem was used to combine the a-priori risk from maternal characteristics and medical history with AFP. Serum AFP was measured in 17 071 cases at 11вЂ“13 weeks, in 8583 cases at 19вЂ“24 weeks and 8609 cases at 30вЂ“34 weeks' gestation.

To examine the distribution of maternal serum alpha-fetoprotein (AFP) at 12, 22 and 32 weeks' gestation in singleton pregnancies which develop pre-eclampsia (PE) and examine the performance of this biomarker in screening for PE.

Sonogram at 4 weeks