Objectives Many maternal factors may influence fetal growth including nationality, smoking, high blood pressure, diabetes and socio-economic level. Twins also have a different growth curve than single babies.
This lesson plan uses graphs to show students how the growth curves may vary due to these different conditions. It also indicates that growth always levels off towards term (40 weeks from last menstrual period) probably because the placenta is no longer adequate to supply the fetus.
Fetal Growth Curve
1. There are a set of transparencies at the Teachers Institute, one for each growth curve, which may be superimposed on each other using an overhead projector. They are based on the following graph from Gruenwald (1966).
2. Give each student his/her own graph (copy next page). First have them convert the weights on the ordinate from grams to pounds by multiplying by. 0022.
Transparency I: Average fetal growth curve
. Before you show it to class ask them to guess the average weight of a baby at term (40 weeks). Have them draw in the curve on their graphs from the transparency.
4. Repeat with the other overlays. Ask students to
a) guess the weight at term for each variable;
b) figure out why it varies from the average; and
c) draw the curve on their graphs.
5. Discuss why the curves level off after 40 weeks. (The placenta seems to age and is no longer capable of supplying the fetus with all its needs.)
(From P. Gruenwald.
Am J Obstet Gynec
(Figure available in print form)
WHAT AFFECTS FETAL GROWTH?
(figure available in print form)