One complication, three different numbers
Per live births, per hospital deliveries and per pregnancies are not the same thing, and the gap between them is not small.
Three data systems produce almost all the numbers you will be quoted. They count different things.
| System | What it counts | What it leaves out |
|---|---|---|
| Birth certificates (NCHS) | Live births. 3,628,934 in 2024. | Miscarriage, stillbirth, termination, ectopic pregnancy, anything that ended before delivery |
| Hospital discharge records | Hospital deliveries. 6,892,304 across 2018 and 2019 in the CDC study. | Births outside a hospital (1.6% of 2024 US births were home births) and early losses managed as outpatients |
| Pregnancies | Everything above added together | No current US figure exists at all |
Here is why that matters at the level of a single sentence. Heavy bleeding after birth is recorded in 4.3% of hospital deliveries. Gestational diabetes is recorded in 8.5% of live births. Miscarriage happens in about 15 of every 100 recognised pregnancies, on a global pooled estimate. Those three numbers cannot be added together, subtracted from one another, or put on the same chart. They do not share a bottom.
The same procedure, two correct rates. Forceps and vacuum births were 2.7% of all live births in 2024. In a study that counted only deliveries where labor was actually attempted, the rate was 3.9%. Both are right. The second excludes scheduled cesareans, which cannot end in a forceps birth. Quoting one while implying the other is the error.
up to 10% of pregnancies. The same document defines it as an estimated fetal weight or abdominal circumference
below the 10th percentile for gestational age. A condition defined as the bottom tenth will, by construction, be found in close to a tenth of the babies measured. The figure is mostly a statement about where the line was drawn. The specialists say so themselves, noting the difficulty of telling apart a baby who is simply small from one who is not growing as it should.
"Is that out of all births, or out of women in my situation?"
"Is that a diagnosis based on a threshold, or on something going wrong?"