Around the seventh or eighth month, babies have reached many milestones. At this age, most infants are already sitting up and crawling — or at least wriggling — around the floor. The majority of 7- and 8-month-olds have also started to consume solid foods, even if it's just baby cereal and purees. Activity levels and diet are just two of the factors that can impact a 7- or 8-month-old's weight.
Many parents worry about their baby’s weight and, more particularly, about their baby’s weight percentile. At each well visit, pediatricians measure a baby’s height, weight and head circumference and assign these measurements a percentile to ensure that an infant is within normal ranges. However, measurements outside normal ranges are not necessarily cause for concern. Doctors reiterate that all babies are different, and they grow at different rates, sometimes faster and sometimes slower than other infants of the same age.
While doctors use growth charts to compare a 7- or 8-month-old baby’s weight to the weights of other infants of the same age, doctors consider a baby’s individual development to be more important. Doctors look to see that a baby is gaining weight, rather than losing or maintaining weight. However, physical growth rates are different from one infant to the next, as babies experience growth spurts and plateaus at different times. Weight at this time should indicate that a baby is progressing toward this goal. That said, many babies’ physical growth slows down after the 6-month mark, so a baby’s weight during the seventh or eighth month does not necessarily reflect growth as rapid as that observed during the first six months.
Genetics, gender, nutrition, physical activity, environment and hormones are important factors that impact weight. Between 7 and 8 months, babies are still on breast milk or formula, with formula-fed babies tending to weigh more than breastfed babies. However, most 7- to 8-month-olds have begun to eat solid foods, in addition to milk or formula. The introduction of solid foods may cause some weight gain. Yet, these babies are also beginning to be more mobile, as they learn to sit up without support and wiggle around on the floor. An infant’s diet and activity levels are bound to affect his weight. An infant’s weight at birth will also impact his weight; for example, it takes a preemie several years to catch up to his peers.
According to KidsHealth, an average 7-lb. newborn will likely weigh around 17 or 18 lbs. at the age of 7 months. At that age, the 50th percentile weight is 17 lbs. for females and 18.5 lbs. for males. At 8 months, an average 7-lb. newborn will likely weigh around 18 or 20 lbs. For females, the 50th percentile weight is 18.5 lbs. and, for males, the 50th percentile weight is 19.5 lbs.