A premature birth means that your baby hasn't had the usual amount of time to develop in the womb before needing to adapt to life outside the womb.

The signs that a baby's gestation has been cut short include:

  • Small size, with a disproportionately large head
  • Sharper looking, less rounded features than a full-term baby's features, due to a lack of fat stores
  • Fine hair (lanugo) covering much of the body
  • Low body temperature, especially immediately after birth in the delivery room, due to a lack of stored body fat
  • Labored breathing or respiratory distress
  • Lack of reflexes for sucking and swallowing, leading to feeding difficulties

The following tables show the median birth weight, length and head circumference of premature babies at different gestational ages for each sex.

Weight, length and head circumference by gestational age for boys
Gestational age Weight Length Head circumference
40 weeks 7 lbs., 15 oz.
(3.6 kg)
20 in. (51 cm) 13.8 in. (35 cm)
35 weeks 5 lbs., 8 oz.
(2.5 kg)
18.1 in. (46 cm) 12.6 in. (32 cm)
32 weeks 3 lbs., 15.5 oz.
(1.8 kg)
16.5 in. (42 cm) 11.6 in. (29.5 cm)
28 weeks 2 lbs., 6.8 oz.
(1.1 kg)
14.4 in. (36.5 cm) 10.2 in. (26 cm)
24 weeks 1 lb., 6.9 oz.
(0.65 kg)
12.2 in. (31 cm) 8.7 in. (22 cm)
Weight, length and head circumference by gestational age for girls
Gestational age Weight Length Head circumference
40 weeks 7 lbs., 7.9 oz.
(3.4 kg)
20 in. (51 cm) 13.8 in. (35 cm)
35 weeks 5 lbs., 4.7 oz.
(2.4 kg)
17.7 in. (45 cm) 12.4 in. (31.5 cm)
32 weeks 3 lbs., 12 oz.
(1.7 kg)
16.5 in. (42 cm) 11.4 in. (29 cm)
28 weeks 2 lbs., 3.3 oz.
(1.0 kg)
14.1 in. (36 cm) 9.8 in. (25 cm)
24 weeks 1 lb., 5.2 oz.
(0.60 kg)
12.6 in. (32 cm) 8.3 in. (21 cm)

Premature babies can quickly develop serious complications, such as infection in the bloodstream (sepsis) and respiratory distress syndrome.

When to see a doctor

You'll be seeing members of the neonatal intensive care unit (NICU) often. Doctors often visit NICUs at a similar time each day. But, don't hesitate to ask questions even when there's not a regularly scheduled meeting, especially if your baby seems listless, has poor color, or refuses the bottle or breast after trouble-free feedings.

Nov. 27, 2014

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