Baby Weight Gain: What's Normal in the First Year
Healthy babies double their birth weight by around 5 months and triple it by 12 months. Week-to-week variation is normal, but consistent growth following a growth curve is the key indicator of good health.
Key Takeaways
- Newborns typically lose up to 10% of birth weight in the first 3–5 days — this is normal; concern arises above 10%.
- Babies should regain their birth weight by 10–14 days; failure to do so by 2 weeks warrants a pediatrician visit.
- Expected gain: 150–200g/week (months 0–3), 100–150g/week (months 3–6), 70–90g/week (months 6–12).
- Growth percentile is less important than consistency — a baby following the 5th percentile is as healthy as one at the 95th.
- The WHO recommends using WHO growth charts (not CDC) for babies up to 24 months, as they are based on exclusively breastfed infants in optimal conditions.
Birth Weight and First Days
Normal Newborn Weight
- Average birth weight: 3.4 kg (7.5 lbs), range typically 2.5–4.5 kg
- Babies below 2.5 kg (5.5 lbs) are considered low birth weight
- Large for gestational age: >4 kg (8.8 lbs) at term
Normal Weight Loss After Birth
Almost all newborns lose weight in the first days — this is expected and normal:
| Days After Birth | Normal Weight Loss |
|---|---|
| Days 1–3 | Up to 7–10% of birth weight |
| Day 4–5 | Weight loss stops, begins to plateau |
| Days 10–14 | Should regain birth weight |
If baby loses >10% or hasn't regained by 2 weeks — call your pediatrician.
Expected Weight Gain: First Year
| Age | Weekly Gain | Monthly Gain | Milestone |
|---|---|---|---|
| 0–3 months | 150–200g (5–7 oz) | 600–800g | Rapid growth phase |
| 3–6 months | 100–150g (3.5–5 oz) | 400–600g | Birth weight doubled ~5 months |
| 6–9 months | 70–90g (2.5–3 oz) | 300–360g | Growth slowing |
| 9–12 months | 60–70g (2–2.5 oz) | 240–280g | Birth weight tripled ~12 months |
Growth Percentiles: Understanding the Chart
Growth percentile charts (WHO Child Growth Standards or CDC charts) show how your baby compares to a reference population.
Key principles:
- There is no ideal percentile. A healthy baby at the 5th percentile is as normal as one at the 95th
- Consistency matters most. A baby should roughly follow their own curve
- Watch for crossing percentiles. Dropping or rising 2+ major percentile lines warrants evaluation
WHO vs. CDC Charts
- WHO (recommended to 24 months): Based on exclusively breastfed babies in optimal conditions, represents how babies should grow
- CDC: Based on US population data including formula-fed babies
Signs of Poor Weight Gain (Failure to Thrive)
Contact your pediatrician if:
- Weight loss >10% in first week
- Not regained birth weight by 2 weeks
- Gains less than 20g/day in first month
- Drops 2+ percentile lines on growth chart
- Fewer than 6 wet diapers/day
- Seems constantly hungry or never satisfied
- Appears lethargic or unwell
Common Causes of Poor Weight Gain
| Cause | Signs | Solution |
|---|---|---|
| Insufficient breast milk | Always hungry, poor output | Lactation consultant |
| Poor latch | Painful feeding, clicking sounds | Lactation consultant |
| Tongue tie | Difficulty latching | ENT referral |
| Medical condition | + other symptoms | Pediatrician workup |
Growth Spurts: When Babies Want to Feed More
Growth spurts temporarily increase feeding frequency and fussiness:
- Week 2–3
- Week 6
- 3 months
- 6 months
- 9 months
- 12 months
During growth spurts, feed on demand. Supply will increase to meet demand within a few days.
🔗 Track your baby's weight and plot it on WHO growth charts with our Growth Tracker.
Sources: WHO Child Growth Standards 2006; American Academy of Pediatrics (AAP). Newborn Weight Loss and Gain; NHS UK. Your Baby's Weight; CDC. Growth Charts
Frequently Asked Questions
How much weight should a baby gain per week?
In the first 3 months, babies gain approximately 150–200g (5–7 oz) per week. From 3–6 months, about 100–150g per week. From 6–12 months, 70–90g per week. By 5 months, most babies double their birth weight; by 12 months, they triple it.
How much weight do newborns lose after birth?
It is normal for newborns to lose up to 10% of birth weight in the first 3–5 days as they pass meconium and adjust to feeding. Most babies regain their birth weight by 10–14 days. Weight loss exceeding 10%, or failure to regain birth weight by 2 weeks, warrants a call to your pediatrician.
What does it mean if my baby drops percentiles on the growth chart?
Dropping 1–2 minor percentile lines early on is often normal as babies settle into their genetic growth curve. However, crossing 2 or more major percentile lines downward (e.g., from 75th to 25th) is a sign that warrants evaluation. Your pediatrician monitors this at every well-child visit.
Is a baby at the 5th percentile healthy?
Yes — percentile position alone does not determine health. A baby consistently following the 5th percentile is growing normally. What matters is that the baby follows their own curve rather than dropping significantly. Genetics play a major role in size.
Sources
- AAP — Developmental milestones for children
- CDC — Learn the Signs. Act Early. — milestone tracking
- WHO — Child health and development
🔧 Helpful Tools
- Baby Milestones Tracker — Track your baby's developmental milestones
- Development Leaps — Understand your baby's developmental leaps
- All Baby Tools — Browse all free tools for pregnancy and baby care
