Placental weight and its ratio to birth weight in normal pregnancy at Songkhlanagarind Hospital.
Level 4 - case-series / case-control
Prospective cross-sectional observational study
What was done
A prospective cross-sectional study evaluated 238 normal pregnancies delivered between 36 and 40 gestational weeks during 2004 at Songkhlanagarind Hospital in Thailand. Trimmed and drained placentae were weighed, distribution curves for placental weight and placental-to-birth-weight ratios were constructed, and intrapartum and perinatal outcomes were compared across percentile categories (<10th percentile, normal, >90th percentile) using Fisher's exact test.
What was found
Placental weight positively correlated with birth weight (r = 0.450, p < 0.005). Across 36–40 weeks of gestation, the mean placental weight was 519 g (SD = 89.01 g), and the mean placental weight to birth weight ratio was 17.08% (decreasing slightly with advancing gestational age). Placental weight below the 10th percentile (p = 0.003) and a ratio below the 10th percentile (p = 0.02) were both significantly associated with fetal distress. Placental weight above the 90th percentile was significantly associated with newborn admission to the neonatal intensive care unit (p = 0.016).
Why it matters
This study provides normative reference data for placental weight and placental-to-birth-weight ratios in a Thai hospital cohort. It demonstrates that extreme deviations in placental size are linked to acute intrapartum complications and neonatal morbidity even within clinically normal pregnancies.
Limits
The study is limited by a modest sample size (n = 238) from a single center, which limits generalizability to broader populations. The cross-sectional design cannot establish causality, and potential confounding variables (such as maternal BMI, parity, or specific indications for NICU admission) were not detailed in the abstract.
Cited by
- contradicts A typical cord blood collection yields about 100 milliliters of blood, while a human placenta weighs roughly 1 kilogram.