| Characteristic | Preterm | Term |
|---|
| Head | Oval—narrow biparietal; large in proportion to body; face looks like “old man” | Square-shaped biparietal prominences; ¼ body length |
| Ears: form, cartilage | Soft, flat, shapeless | Pinna firm; erect from head |
| Hair: texture, distribution | Fine, fuzzy, or wooly; clumped; appears at 20 weeks | Silk; single strands apparent |
| Sole creases | Starting at ball of foot: ⅓ covered with creases by 36 weeks,  by 38 weeks | Entire sole heavily creased |
| Breast nodules | 0 mm at 36 weeks; 4 mm at 37 weeks | 10 mm or more |
| Nipples | No areolae | Formed; raised above skin level |
| Genitalia |
| Clitoris large, labia gaping | Labia larger, meet in midline |
| Small scrotum, rugae on inferior surface only, and testes undescended | Scrotum pendulous, covered with rugae; testes usually descended |
| Skin: texture, opacity | Visible abdominal veins; thin, shiny | Few indistinct larger veins; thick, dry, cracked, peeling |
| Vernix | Covers body by 31–33 weeks | Small amount in creases or absent at term; postterm: dry, wrinkled |
| Lanugo | Apparent at 20 weeks; by 33–36 weeks, covers shoulders | Minimal or no lanugo (depends on parental ethnicity) |
| Muscle tone | Hypotonia; extension of arms and legs | Hypertonia; well flexed |
| Posture | Froglike | Attitude of general flexion |
| Head lag | Head lags; arms have little or no flexion | Head follows trunk; strong arm flexion |
| Scarf sign | Elbow can extend to opposite axilla | Elbow to midline only; infant resists |
| Square window | 90 degrees | 0 degrees |
| Ankle dorsiflexion | 90 degrees | 0 degrees |
| Popliteal angle | 180 degrees | <90 degrees |
| Heel-to-ear maneuver | Touches ear easily | 90 degrees |
| Ventral suspension | Hypotonia; “rag-doll” | Good caudal and cephalic tone |
| Reflexes |
| Apparent at 28 weeks; good, but no adduction | Complete reflex with adduction; disappears 4 months postterm |
| Fair at 28 weeks; arm is involved at 32 weeks | Strong enough to sustain weight for a few seconds when pulled up; hand, arm, shoulder involved |
| Cry | 24 weeks: weak; 28 weeks: high-pitched; 32 weeks: good | Lusty; can persist for some time |
| Length | Under 47 cm (18½ inches), usually | 50 cm (20 inches); range: 18–22 inches |
| Weight | Under 2500 gm (5 lb 5 oz) | 3400 gm (7½ lb); range: 5 lb 8 oz–8 lb 13 oz |