Placental thickness in the first half of pregnancy

Purpose: This study was conducted to establish normal values of placental thickness during the first half of pregnancy.

Methods: Normal pregnant women with singleton pregnancies between 8 and 20 weeks of gestation were recruited into the study. All the newborns were normal at birth. Placental thickness was measured perpendicularly through the thickest part of the placenta on transabdominal scans. The placental thickness data were analyzed for mean, standard deviation, 95% confidence interval, and 2.5(th), 5(th), 50(th), 95(th), and 97.5(th) percentile for each week of gestational age. The best-fit mathematical model was derived by regression analysis.

Results: The total number of measurements was 333 and the number of measurements for each week of gestational age ranged from 9 to 37. Regression analysis yielded the following linear equation of the relationship: placental thickness (in mm) = gestational age (in weeks) x 1.4-5.6 (r = 0.82).

Conclusion: We have established a nomogram for placental thickness. This resource may be a useful aid in the early detection of placental abnormalities, such as hydropic placenta secondary to hemoglobin Bart's disease.