A clinically oriented scoring system for placental pathology tested in late-onset fetal growth restriction and...

Fetal growth restriction (FGR) is thought to originate from placental insufficiency, but late-onset FGR fetuses often lack signs of impaired uteroplacental circulation in Doppler sonography and distinction from small for gestational age (SGA) is challenging. SGA fetuses are often mistaken for constitutionally small and healthy. We aimed to investigate placental pathology in late-onset FGR and SGA compared to controls and to validate a novel semiquantitative scoring system for its clinical utility.

In this prospective cohort study of singleton pregnancies ≥32 weeks, placentas from late-onset SGA were examined in comparison to controls. The SGA cohort was subdivided into FGR (birthweight <3rd percentile and/or pathological Doppler) and SGA 3rd-10th percentile (remaining cases with normal Doppler). Placental pathology was assessed based on the Amsterdam Criteria.

A total of 41 placentas were evaluated (13 FGR, 10 SGA 3rd-10th and 18 controls). FGR placentas showed higher cumulative scores and more frequently morphological signs of placental insufficiency, while SGA 3rd-10th and controls mostly showed lesions with compensatory changes. Maternal vascular malperfusion (MVM) lesions were observed in 100% of FGR, 80% of SGA 3rd-10th and 27.8% of control placentas.

This study reveals a high prevalence of placental lesions, particularly MVM, in late-onset FGR pregnancies, but also in late-onset SGA without Doppler abnormalities. The novel scoring system shows promise as a practical tool for reproducible placental evaluation and may improve postnatal identification of clinically significant placental insufficiency. These findings underline the importance of routine placental examination and the need for further standardization of diagnostic criteria.