Click Here for an animation about embyonic and fetal growth from the University of Pennsylvania
One of the ways of following fetal growth is by calculating weight from ultrasonic measurements of different parts of the body. We pay most attention to this in the third trimester, when differences in growth patterns begin to emerge. We want to identify fetuses that are larger or smaller than the average at each gestational age, because this will have some important conequences for deciding when and how a child should be delivered.
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Average
weight a birth correllates with a lot of factors, including length of
gestation, maternal pre-pregnancy height and weight, parity (# of
pregnancies), ethnicity, fetal sex, and possibly even season. Babies
tend to weight a little more and to be born a bit sooner over the first
three pregnancies, with girls usually weighing about a half a pound
less than boys. |
One of the ways we look at the growth process is by looking at the fraction of the 40 week (term) weight that a fetus reaches at each week of gestation. Half of the term weight is reached at 31.4 weeks. Representative data are presented as a table. The pattern is a perfect spiral when presented as a polar graph of percent versus gestational age.
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This is a general growth pattern, identical for all normal fetuses, everywhere in the world.
