Preeclampsia and late fetal growth restriction

There is a strong but complex relationship between fetal growth restriction and preeclampsia. According to the International Society for the Study of Hypertension in Pregnancy the coexistence of gestational hypertension and fetal growth restriction identifies preeclampsia with no need for other signs of maternal organ impairment. While early-onset fetal growth restriction and preeclampsia are often strictly associated, such association becomes looser in the late preterm and term periods. The incidence of preeclampsia decreases dramatically from early preterm fetal growth restriction (39-43%) to late preterm fetal growth restriction (9-32%) and finally to term fetal growth restriction (4-7%). Different placental and cardiovascular mechanism underlie this trend: isolated fetal growth restriction has less frequent placental vascular lesions than fetal growth restriction associated with preeclampsia; moreover, late preterm and term fetal growth restriction show different patterns of maternal cardiac output and peripheral vascular resistance in comparison with preeclampsia. Consequently, current strategies for first trimester screening of placental dysfunction, originally implemented for preeclampsia, do not perform well for late-onset fetal growth restriction: the sensitivity of first trimester combined screening for small-for-gestational age newborns delivered at less than 32 weeks is 56-63%, and progressively decreases for those delivered at 32-36 weeks (43-48%) or at term (21-26%). Moreover, while the test is more sensitive for small-for-gestational age associated with preeclampsia at any gestational age, its sensitivity is much lower for small-for-gestational age without preeclampsia at 32-36 weeks (31-37%) or at term (19-23%).