Facial expressions and other movements inside the womb reflect the extent of development of the fetus’ brain and central nervous system. A new study from Japan reports on the first use of 4D ultrasound recordings to track different facial expressions in twin fetuses, providing some insight into their behavior in different stages of growth before birth.
By Toshiyuki Hata
Based on the knowledge that facial motions can reflect the extent of brain development inside the womb, researchers from Japan recorded seven different expressions – among others smiling, blinking and yawning – in 30 singleton (individual) fetuses and 30 twin fetuses.
By using 4D ultrasound, a technique that resembles live video, they were able to track these expressions at around 30 weeks of gestation. They then compared the frequencies of the different facial expressions between twins and singletons.
Twins show less facial expressions in the womb
“The limitation of available space and crowding of twins with advancing gestation may have a marked impact on twin fetal movements compared with singleton fetuses, even in the first half of pregnancy,” said Dr. AboEllail, one member of the research team. The effect of limited space might persist until the third trimester of pregnancy, and become reflected in fetal behavior.
Crowding represents an unfavorable condition inside the womb resulting in accelerated maturation of some parts of the brain. According to the researchers, mouthing movements decrease with the advancement of gestation as a sign of brain maturation and development. The effect can be seen in the decreased frequencies of facial expressions in twins compared with singleton fetuses.
For future research, the team would be interested to know whether the effect of the limited space in the womb affects brain development also after birth.
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