4D ultrasound study of fetal facial expressions in the third trimester of pregnancy

Objective: To evaluate the frequencies of fetal facial expressions in the third trimester of pregnancy, when fetal brain maturation and development are progressing in normal healthy fetuses.

Methods: Four-dimensional (4?D) ultrasound was used to examine the facial expressions of 111 healthy fetuses between 30 and 40?weeks of gestation. The frequencies of seven facial expressions (mouthing, yawning, smiling, tongue expulsion, scowling, sucking, and blinking) during 15-minute recordings were assessed. The fetuses were further divided into three gestational age groups (25 fetuses at 30–31?weeks, 43 at 32–35?weeks, and 43 at ≥36?weeks). Comparison of facial expressions among the three gestational age groups was performed to determine their changes with advancing gestation.

Results: Mouthing was the most frequent facial expression at 30–40?weeks of gestation, followed by blinking. Both facial expressions were significantly more frequent than the other expressions (p?p?=?.031). Other facial expressions did not change between 30 and 40?weeks. The frequency of yawning at 30–31?weeks was significantly higher than that at 36–40?weeks (p?Conclusions: Our results suggest that 4D ultrasound assessment of fetal facial expressions may be a useful modality for evaluating fetal brain maturation and development. The decreasing frequency of fetal yawning after 30?weeks of gestation may explain the emergence of distinct states of arousal.