After birth, a track of weight, length, and head size is maintained by the doctors. A healthy baby grows fast. Poor growth is considered as a sign of an underlying health problem. It is observed that during first year, newborns grow a big way. Most of the infants triple their original weight during first year, and also increase their length by about 50%. Premature babies are born with much less than normal weight and length, and so need to be kept at the NICU for a few days. Parents of premature babies should follow a preemie growth chart.
Average Weight of an Infant at Birth
If your baby weighs anywhere between 5.5 – 10 lbs (2.7-4.6 kg), he /she would be considered as healthy, as this is the normal range for birth weight in developed countries. A baby weighing slightly less or high is also considered as healthy, as it would be close to normal. The average weight of a newly born infant is different for developed and non-developed countries. Even for the scientists and researchers, it is difficult to determine the ideal average weight at birth, because it depends upon various factors. In developed countries, the average weight of a full-term newborn is 7.5 lbs (3.4 kg).
Factors that Determine the Weight
- Duration of the pregnancy, if it is a preterm birth, the baby is likely to be underweight
- Rate of fetal growth
- Infant Gender
- Whether it is a singleton pregnancy, or it is a case of multiple births
- Size of the parents
- Birth order
- Any complications regarding baby’s health
- Maternal factors, such as race and ethnicity, nutrition, and current and previous pregnancy medical risk characteristics.
- According to the available statistics, the median birth-weight for U.S. singleton, full-term (forty weeks of gestation) births is nearly 3,500 grams (7 pounds, 11 ounces), and about 80% of the newborn infants have weight between 6 pounds and 9 pounds 4 ounces (2,750-4,250 grams).
- In the developed world, where there is no malnutrition of mothers, where mothers enjoy the benefits of advanced technology, the average weight of a full-term newborn is approximately 7 ½ lbs or 3.4 kg. It is typically in the range of 5.5-10 pounds (2.7-4.6 kg).
- Statistics show that the average weight at birth of boys and girls has increased marginally. The median birth weight in the period 1989-1991 was 3,372 grams, compared to 3,434 grams in the period 2004-2006.
- The average total body length of the newborn infants ranges from 14-20 inches (35.6-50.8 cm), although premature newborns may be much smaller. The average length of newborn boys and girls is 50.6 and 50.1 cm respectively. Approximately four percent newborn babies are smaller than 46 cm.
- The weight should not vary according to the gender. But, studies show that boys usually weigh 100 grams more than girls, at birth. Generally, boys are slightly heavier in weight than girls.
- Over 5 percent of newborn babies have a lower than average weight, i.e. less than 2,500 grams.
- Approximately 0.08 percent babies have an extremely low weight, i.e. less than 1,500 grams.
- Forty weeks is the normal duration of a singleton pregnancy. For twins, pregnancy may last for 37 weeks, while for a triplet pregnancy, it may last for 34 weeks. Approximately 50% of all multiple births are premature.
- Statistical reports show that the more the number of babies, chances of premature delivery are higher. Higher order multiples are always at the risk of prematurity, and they generally have a very low weight as well.
- Statistical analysis of the data collected during research studies reveal the fact that 58.2% of all multiple birth children were born lower than average weight, whereas only 6.2% of singletons were born low weight.
- The average birth weight of twins is 5 lbs. 5 oz. It is not necessary that the babies born as twins will have the same weight. Weight of each baby will be different. Sometimes, there can even be a difference of 2-3 pounds.
Scientists, all over the world, are researching on the close relationship between the birth weight and the risk of dying within the first year of life. Since infants with low weight are always at grave risk of mortality, weight of a newborn is considered by the researchers as a measure of mortality risk. Infants with lower than normal weight at the time of birth, usually suffer from various diseases and long-term developmental problems. Genetics, good nutrition, love, affection, and attention determine how your baby grows in the years to come. Whether your baby is born large, small, or in between, it doesn’t matter. You can always expect your baby to grow fast in the next few months.