Is 9.5 lb normal for a 0-month-old girl?
| PercentileUpper quarter of the chart · CDC weight-for-age | 84th |
|---|---|
| Weight4.31 kg — the unit the chart is built in | 9.5 lb |
| Z-scorestandard deviations from the median | 1 |
| Median for this age3.8 kg — the 50th percentile | 8.4 lb |
| 5th percentile weight | 6.4 lb |
| 95th percentile weight | 10.2 lb |
| Median length at this age51.7 cm | 20.3 in |
| Median head circumference36 cm | 14.2 in |
Notes
- The percentile is not a score, and the middle is not a target. By definition 5% of perfectly healthy children sit below the 5th percentile and 5% above the 95th, because the chart describes a population rather than prescribing a weight. A child at the 10th percentile who has been at the 10th percentile since birth is growing normally; the same child arriving there from the 60th over three months is the situation that gets attention. Clinicians watch the curve, not the point.
- CDC recommends the WHO charts for children under 24 months, not this one. The WHO standard was built from exclusively breastfed infants under ideal conditions and describes how children should grow; the CDC chart describes how a mixed US sample did grow. In practice a breastfed baby often plots one or two bands lower on the CDC chart than on the WHO chart during the first year, which is a frequent and avoidable cause of worry. If your paediatrician's chart disagrees with this page in the first two years, that difference is very likely the reason.
- Weight only means something next to length. A baby at the 15th percentile for weight and the 15th for length is proportionate; one at the 15th for weight and the 75th for length is a different picture entirely. Weight-for-length, plotted on its own chart, is what separates them, and it is the figure a check-up actually uses.
- Corrected age matters if the baby was premature. Growth charts run from the due date, not the birth date, so for a baby born eight weeks early you plot at 0 months minus two. Doing otherwise makes a normally growing premature baby look as if it is falling behind, and correction is standard until about two years of age.
- Measuring a baby accurately is harder than it sounds. Weigh naked or in a dry nappy of known weight, on the same scale, at roughly the same time of day; a feed and a nappy together can account for half a pound. Length needs two people and a firm surface — a tape measure along a wriggling baby is routinely out by an inch, which is enough to move the percentile by twenty points.
Where 9.5 lb sits for a 0-month-old girl
A weight of 9.5 lb (4.31 kg) at 0 months puts a girl at the 84th percentile on the CDC weight-for-age chart — in the upper quarter of the CDC chart.
The median for this age is 8.4 lb. The 5th percentile is 6.4 lb and the 95th is 10.2 lb, so the middle nine children in ten weigh somewhere between those two.
What a percentile is, and what it is not
A percentile compares one child to a reference population of children the same age and sex. The 84th percentile means roughly that share of children weigh less. It is a position on a distribution, not a mark out of a hundred, and there is no percentile that is the right one to be at.
The number that carries information is the direction of travel. A child who has tracked the same band since birth is growing the way that child grows. A child who crosses two bands downward over a few months is the one a check-up will want to look at, even if the new band is still comfortably inside the normal range.
Nearby sizes
Read more
- Percentiles and Spurts — The Curve Matters, the Number Does NotParents read the percentile as a score. It is a position in a distribution, and half of all healthy babies are below the fiftieth by definition.
- Baby Length by Age: WHO Tables, and Why It Is Measured Lying DownLength is the hardest of the three growth measurements to take accurately, which is why it looks noisier on a chart than it really is.
- Head Circumference by Age: The Measurement Nobody MentionsIt is taken at every well-baby visit and explained at almost none of them. Head circumference tracks brain growth, and its trend line is watched more closely than weight.
- Baby Weight Percentile by Month: WHO Tables for the First YearThe full month-by-month table for the first year. The number it gives you is the least important thing on the page.