Most babies slow in gaining weight within the first nine months catch up by the age of 13, but remain lighter and shorter than their peers, a new study has found.
The University of Bristol study is based on data from 11,499 participants, providing the most conclusive and reassuring evidence for parents that, given the right care, many infants who lag in weight gain catch up by teenage.
Alan Emond, professor at Bristol, who led the study, explains: "The reason the early group caught up more quickly may be because those infants had obvious feeding difficulties and were more readily identified at the eight-week check, resulting in early treatment leading to a more rapid recovery, the journal Paediatrics reports.
"Those children who showed slow weight gain later in infancy took longer to recover, because of the longer period of slow growth and because their parents were smaller and lighter too," adds Emond, according to a Bristol statement.
The study found that, of the 11,499 infants born at term, 507 were slow to put on weight before the age of eight weeks (early group) and 480 were slow to gain weight between eight weeks and nine months (late group).
Thirty children were common to both groups.
The infants in the early group recovered quickly and had almost caught up in weight by the age of two, whereas those in the later group gained weight slowly until the age of seven, then had a 'spurt' between seven and 10 years, but remained considerably shorter and lighter than their peers and those in the early group at the age of 13.
At that age, children in the later group were on average 5.5 kg lighter and almost four cm shorter than their peers; those in the early group were on average 2.5 kg lighter and 3.25 cm shorter than their peers, according to a Bristol statement.
Slow weight gain is often seen by parents and some healthcare professionals as a sign of underlying ill health. Clinicians face a dilemma between taking steps to increase a child's energy intake and putting them at risk of obesity later in life by encouraging too rapid weight gain.