Most babies lose 5–10% of their birth weight in the first few days, then regain it by 10–14 days. After that, the NHS expects babies to gain approximately: 150–200g/week in the first 3 months, 100–150g/week at 3–6 months, 70–90g/week at 6–12 months. Weight gain varies week to week — trends over 2–4 weeks matter more than any single weigh-in.
These WHO reference ranges cover the 3rd–97th centiles. Staying on or near the same centile over time is more important than which centile your baby is on.
Frequently Asked Questions
Dropping one centile space is usually not concerning, especially in the first few weeks. Dropping two or more centile spaces, or falling below the 2nd centile, warrants a conversation with your health visitor or GP. Combined with other signs (poor feeding, fewer wet nappies, lethargy), seek advice sooner. One low weight reading in an otherwise thriving baby is rarely cause for alarm.
The NHS recommends weighing newborns at birth, day 5, and day 10–14 to confirm birth weight regain. After that: monthly up to 6 months, every 2 months from 6–12 months, quarterly from 1–2 years. More frequent weighing can cause unnecessary anxiety without clinical benefit. Your health visitor will advise based on your baby's individual growth pattern.
Yes — breastfed babies sometimes gain weight slightly more slowly in the early months and may look slimmer than formula-fed babies. The WHO growth charts used in the UK are based on breastfed infants and reflect optimal growth. Differences typically even out by 12 months. If you're concerned about weight gain alongside breastfeeding, a lactation consultant can assess feeding effectiveness.