Prediction of preeclampsia by uterine artery Doppler at 1824 weeks gestation

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Low-risk pregnancies

Based on a review of 19 studies, Papageorghiou et al. (2002) found an overall sensitivity of uterine artery Doppler for predicting pre-eclampsia of 55% but this ranged from 24% to 89%. The pooled likelihood ratio (LR) for a positive result (LR+) was 5.90 (5.30, 6.52) while the pooled LR for a negative result was 0.55 (0.50, 0.60). Lees et al. (2001) subsequently showed that likelihood of severe adverse pregnancy outcome (fetal death, abruption

Uterine Artery With Gestation Age

Figure 32.4 Prediction of adverse outcome by uterine artery Doppler at 23 weeks. Likelihood ratio (vertical axis) for severe adverse outcome (fetal death, pre-eclampsia before 34 weeks, small-for-gestational age fetus [<10th centile] before 34 weeks, placental abruption) relating to mean pulsatility index (horizontal axis). Smokers are represented by a thick block line, nonsmokers by a thin line. Reproduced from Lees et al. (2001), with permission.

Figure 32.4 Prediction of adverse outcome by uterine artery Doppler at 23 weeks. Likelihood ratio (vertical axis) for severe adverse outcome (fetal death, pre-eclampsia before 34 weeks, small-for-gestational age fetus [<10th centile] before 34 weeks, placental abruption) relating to mean pulsatility index (horizontal axis). Smokers are represented by a thick block line, nonsmokers by a thin line. Reproduced from Lees et al. (2001), with permission.

and delivery before 34 weeks associated with preeclampsia and birthweight < 10th centile) increased quadratically with mean uterine artery PI (Figure 32.4); the 95th centile for mean PI was 1.45 and at this level the LR for severe adverse outcome was 5 for nonsmokers and 10 for smokers.

The clinical usefulness of routine uterine artery screening in low-risk women is, however, debatable. Based on the overview of Chien et al. (2000) of 27 studies, uterine artery Doppler has not been recommended for inclusion in routine antenatal care in England (National Collaborating Centre for Women's and Children's Health, 2003). However, the benefit of screening is also influenced by the effectiveness of therapies to prevent or ameliorate pre-eclampsia in screen-positive women.

At present, Doppler screening of uterine arteries, with the aim of reducing pre-eclampsia in screen-positive women, cannot be recommended. If the greater therapeutic benefit of antioxidants (Chappell et al., 1999) versus aspirin therapy is confirmed in large randomized trials this will need to be reviewed. With the current drive to reduce antenatal visits in ''low-risk'' women (National Collaborating Centre for Women's and Children's Health, 2003), the value of a normal uterine artery screen, also needs to be addressed.

High-risk pregnancies

The positive predictive value of uterine artery Doppler is greater in women at high risk of pre-eclampsia based on underlying maternal vascular disease, e.g. SLE, chronic hypertension or renal disease and also in women with previous severe preeclampsia. A recent detailed comparison of screening performance in high-risk women suggested that a mean RI > 0.69 performed as well as a mean PI > 1.51, irrespective of notch status (sensitivity 55%, PPV 72%, NPV 80%) (Friedman et al., 1995).

Application of uterine Doppler in specific patient groups has generally confirmed these results. Recent studies of normotensive women with previous adverse pregnancy outcomes (previous pre-eclampsia, stillbirth, abruption, FGR) have generally reported sensitivities for pre-eclampsia of 78-95% with PPV 39-44% (Coleman et al., 2003; Harrington etal., 2004; Parretti et al., 2003). Studies in women with chronic hypertension have indicated slightly lower PPV (Harrington et al., 2004; Parretti et al., 2003). Perhaps more importantly in these high-risk groups, a normal uterine artery Doppler waveform confers a risk of adverse outcome similar to that of women with an uncomplicated obstetric history or normotension (Frusca et al., 1998; Harrington et al., 2004).

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