Impact of Placental Grading on Pregnancy Outcomes: A Retrospective Cohort Study

Placental grading remains underutilized in clinical practice despite its potential prognostic value. This study aimed to elucidate the relationship between premature placental calcification (PPC) and relevant perinatal outcomes in a large cohort.

We conducted a retrospective cohort study involving 3088 singleton pregnancies that underwent routine third-trimester ultrasound examinations (30⁺⁰ to 35⁺⁶ gestational weeks) at the Third Department of Obstetrics and Gynecology, School of Medicine, Faculty of Health Sciences, Aristotle University of Thessaloniki, Greece, between January 2018 and December 2023. Placental calcification was graded using the Grannum system, categorizing placentas into Grades 0-1 (control), Grade 2, and Grade 3. Primary outcomes assessed were small for gestational age neonates (SGA) and preeclampsia. Secondary outcomes included gestational hypertension, fetal growth restriction (FGR), stillbirth, gestational age at birth, and birthweight centile. Multiple logistic regression was employed to adjust for confounders, i.e., maternal age, BMI, smoking, conception via assisted reproductive technology, and uterine artery pulsatility index.

In total, 544 pregnancies (17.6%) had Grade 2 placentas, and 41 pregnancies (1.3%) had Grade 3 placentas. Compared to the control group, Grade 2 placentas were associated with increased odds of SGA (adjusted odds ratio [aOR] 1.80; 95% confidence intervals [CI]: 1.43-2.25) and FGR (aOR 1.81; 95% CI: 1.35-2.42). Grade 3 placentas showed even higher odds of SGA (aOR 3.09; 95% CI: 1.55-6.17) and FGR (aOR 3.26; 95% CI: 1.53-6.95). No significant associations were found between placental grading and preeclampsia or stillbirth. Additionally, PPC was linked to lower birthweight percentiles and earlier gestational age at birth.

Premature placental calcification (before 36⁺⁰ weeks), particularly Grade 3, is significantly associated with adverse perinatal outcomes such as SGA and FGR. Incorporating placental grading into routine prenatal care may enhance risk stratification and guide clinical decision making beyond traditional assessment methods.