Have newborns been too large?

kw: observations, news

In the local newspapers and a radio program or two it was reported today that babies have been getting smaller since about 1990. The present average newborn weight in 2005, nationally, was 7 lbs 7.5 oz, down 2 oz over fifteen years. That actually compares well with the average weight of my generation at birth: 7 lbs 6.3 oz (I was born in 1947. Our own son, who is now 21, weighed 7 lbs 10 oz, and came out "naturally").

I actually read in one article that a doctor thinks "optimum" birth weight is nearly nine pounds! Very few women can have a baby that large vaginally. Again, when I was born, weights between seven and eight pounds were considered normal. Nine pounds was a much-talked-about rarity.

I finger as the primary cause a major trend that became prominent in the 1980s: Scheduled birth by Caesarian section. By definition, such a procedure is performed before the baby is ready to be born, so the baby is always pre-term. The tendency to set the schedule earlier and earlier, and the tendency for a growing proportion of all births to be scheduled, work together to produce smaller babies.

A secondary trend is the ability to save earlier and earlier preemies. I can't be sure from what I have read whether the genuinely premature births were included in the averages, but consider this, if they were: in 1950 it was rare for a baby lighter than 4.5 pounds to survive, but now it is considered routine for babies born weighing one pound or less to survive. Think how a large number of such births will skew an average! Much of this trend toward saving the very early occurred since 1980.

The statistic I want to see is the average weights, in several key years (1950, 1980, 1990, 2005 at the very least), of babies born vaginally who suffered no complications and needed no special interventions at birth. I suspect there will be very little difference over the years.