Physical Appearance of a Post-Term Infant at 42 Weeks and 2 Days
A baby born at 42 weeks and 2 days gestation will most commonly appear normal, though approximately 10-20% may show signs of dysmaturity (postmaturity syndrome) characterized by dry, cracked, peeling skin, decreased subcutaneous fat giving a thin or wasted appearance, long nails, and increased alertness. 1
Normal Appearance (Most Common)
The majority of post-term infants appear entirely normal at birth, with no distinguishing features from term infants. 1 Key characteristics include:
- Normal skin texture and color without evidence of wasting 1
- Adequate subcutaneous fat stores 1
- Appropriate muscle mass for gestational age 1
- Normal activity level and tone 1
Dysmature (Postmature) Appearance (10-20% of Cases)
A smaller subset of post-term infants will demonstrate the classic postmaturity syndrome, which becomes more prevalent as gestation extends beyond 42 weeks. 1 These infants exhibit:
Skin Changes
- Dry, cracked, parchment-like skin that may be peeling or desquamating 1
- Meconium staining of the skin, nails, and umbilical cord (greenish-yellow discoloration) if meconium passage occurred in utero 2
- Loss of vernix caseosa (the protective waxy coating normally present at term) 1
Body Habitus
- Decreased subcutaneous fat giving a thin, wasted appearance 1
- Loose, wrinkled skin particularly noticeable on the thighs and buttocks 1
- Long, thin body with reduced soft tissue 1
Other Features
- Long fingernails and toenails that may extend beyond the fingertips 1
- Abundant scalp hair 1
- Wide-eyed, alert appearance with increased alertness compared to term infants 1
- Macrosomia (large birth weight >4000g) may occur in some post-term infants, increasing risk of birth trauma 1, 2
Clinical Context and Monitoring
The incidence of dysmaturity increases progressively as post-term gestation continues, though the absolute prevalence of dysmaturity remains higher in term infants overall. 1 Post-term infants are at increased risk for:
- Meconium aspiration syndrome, with incidence rising from 0.24‰ at 38 weeks to 1.42‰ at 42-43 weeks 2
- Perinatal asphyxia and fetal distress due to placental insufficiency 1, 2
- Polycythemia (elevated red blood cell count) 1
- Neonatal acidosis and low Apgar scores 2
With careful obstetric management and monitoring, most neonatal complications can be prevented, and long-term somatic growth and intellectual development are normal in post-term infants who do not experience perinatal asphyxia. 1