Prediction of adverse pregnancy outcome

Two main groups of adverse pregnancy outcomes are nowadays of utmost interest in obstetrics: preterm labour (PL) and placental diseases including Preeclampsia (PE), Intrauterine Growth Restriction (IUGR) and Intrauterine Foetal Death.
A new concept of prediction in obstetrics has emerged in the 90’s with Nicolaides K. et alt..  An earlier identification of those patients at risk would allow an intensive and more accurate and personalized management algorithms of those, and it would allow initiating preventive strategies in those possible cases. There’s wide evidence  that preventive strategies should be applied early in the pregnancy in order to be more effective, especially in the case of aspirin and PE.
*We will first focus on preterm labour. Several parameters have been described as risk factors of PL. Nevertheless, the most important risk factor is a previous preterm delivery. Earlier the previous delivery was, higher the risk of PL in the current pregnancy would be. Moreover, the risk would be higher as more previous deliveries the patient had.
Nevertheless, only 10% of those patients with a preterm delivery presented risk factors at first trimester.
A prediction strategy at second trimester has been validated as a screening test in low-risk population. Cervical length, evaluated in the second trimester anomaly scan, has proved to identify patients at risk for preterm delivery. 1 out of 5 patients with cervical length below 25 mm will delivery before 35 weeks of gestation.
Prevention strategies mainly based on Progesterone and cervical pessary have proved their efficacy in those patients with short cervical length, reducing the incidence of preterm delivery and the incidence of perinatal morbidity almost 40%.
*We will focus in a second term in the prediction of PE and IUGR.
In order to understand the recent evolution in the prediction algorithms of PE, it is essential to focus on the current classification of PE according to the gestational age at onset of the disease. In recent years it has been accepted that early-onset and late-onset PE are associated with different biochemical, histological and clinical features: whereas the early-onset form is almost invariably associated with placental insufficiency and growth restriction and it mostly contributes to adverse maternal and perinatal outcomes , the late-onset form is more prevalent and in general, placental involvement is minimally present. Moreover, it has been demonstrated that having a PE in a previous pregnancy considerably increases the risk in the following pregnancy.
There are multiple markers of PE, some of them are known at booking and some of them all along the first two trimesters of pregnancy. The former are based on demographic characteristics as medical or obstetric history and anthropometric maternal characteristics and they would generate a prior-risk patient. The latter markers are secondary to the pathophysiological changes preceding the onset of the disease, mainly due to a defective trophoblastic invasion. These markers are especially associated with early-onset PE. As there is no single test that predicts PE with sufficient accuracy to be clinically useful, the current strategies are based on multiparametric algorithms based on maternal history, biochemical markers and uterine Doppler evaluation.
As we have mentioned this approach will be useful in the prediction of early-onset PE but not for late-onset PE. A third trimester prediction strategy has been proposed for the more frequent form of PE. Prevention treatments would not be useful but those patients identified at high risk could benefit of a more intensive monitoring.
The prediction of IUGR would follow the same scheme as PE. Early IUGR could acceptably be predicted in the first trimester using a multiparametric strategy whereas the prediction of late-IUGR could be hardly be made in third trimester.
Placental growth factor (PlGF) has recently emerged as a promising biomarker in the prediction of placental disease, including intrauterine foetal death.
Prediction of severe disease would be possible early in the pregnancy allowing to activating prevention strategies. Deeper investigation should be carried on for the prediction of late and mild placental disease.

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