Neurological and physical maturation in normal growth singletons from 37 to 41 weeks' gestation

An evaluator blinded to gestational age (GA) assessed a cohort of 397 singletons born at between 37 and 41 week's gestation, by looking at 11 criteria exploring neurological maturity and 12 criteria exploring physical maturity. The analysis of correlation coefficients shows various degrees of association between GA and each of the criteria examined. A highly significant correlation (p < 0.001) was found for 4 neurological criteria defining passive tone in limbs and sucking reflex. The activity of flexor muscles of the neck and crossed extension reflex were also associated with maturity but weakly (p < 0.01). A highly significant correlation (p < 0.001) was found for 8 of the physical criteria, skin colour and texture, lanugo, ear firmness, genitalia, breast size, nipple formation and plantar skin creases. Oedema, skull firmness and ear form were also associated but weakly. With multivariate analysis combining the neurological and physical criteria, predictive values ranked in the following order: 1) plantar skin, 2) breast size, 3) sucking reflex, 4) scarf sign, 5) skin colour, 6) genitalia, 7) popliteal angle, 8) return to flexion of forearms, 9) dorsiflexion angle. In conclusion, a score based on physical and neurological criteria is associated with duration of pregnancy (r2 = 0.32) between 37 and 41 weeks' gestation. Such an instrument allows us to study fetal maturity as a variable independent of GA, and therefore makes it possible to identify various influences that may modify maturational rate during the last weeks of pregnancy.