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Published on: August 2, 2017
Placental thickness in the second trimester: a pilot study to determine the normal range
Anna J Lee1, Michael Bethune, Richard J Hiscock
1Royal Women's Hospital, Flemington Road, Parkville, VIC 3052, Australia. anna.lee.email@gmail.com
Summary
Second-trimester placental thickness measurement should account for placental site. Anterior placentas are thinner than posterior or fundal placentas, requiring adjusted normal ranges for accurate assessment.
Area of Science:
- Obstetrics and Gynecology
- Diagnostic Ultrasound
- Fetal Medicine
Background:
- Placental thickness is a key parameter in prenatal ultrasound.
- Establishing normal ranges is crucial for identifying potential fetal growth abnormalities.
Purpose of the Study:
- To determine normal sonographically measured placental thickness during the second trimester (18-22 weeks 6 days).
- To assess the need for adjusting placental thickness measurements based on gestational age and placental site.
Main Methods:
- A cross-sectional observational pilot study.
- Involved 114 consecutive singleton pregnancies undergoing routine second-trimester sonography.
- Measurements taken between 18 weeks and 22 weeks 6 days gestation.
Main Results:
- The overall mean placental thickness was 24.6 mm (SD, 7.29 mm).
- Placental thickness was significantly lower (6.6 mm) in anterior compared to posterior or fundal placentas (P < .001).
- A slight, non-significant increase in thickness was observed with advancing gestational age.
Conclusions:
- Placental position is a critical factor influencing thickness measurements.
- Gestational age may also play a role, though less significant in this study.
- Abnormal thickness thresholds: >33 mm for anterior, >40 mm for posterior placentas.
