Years ago, doctors regularly advised women to strictly limit their weight gain in pregnancy. They viewed this as a way to prevent pre-eclampsia (high blood pressure issues in pregnancy) because one of the symptoms of pre-eclampsia is a high weight gain from retaining fluids.
They decided that the large weight gain must be causing the pre-eclampsia, and therefore, preventing a large weight gain would help prevent pre-eclampsia.
They also wanted to prevent women from having large babies, so they strongly counseled women of all sizes to limit weight gain in order to get a smaller baby.
[Not only did they restrict weight gain, they also advised women to smoke to keep down their weight gain and fetal size, or to use diuretics to prevent fluid retention, both of which were later discovered to cause serious problems in pregnancy. Doh!]
All this was in the name of a worthy goal----preventing pre-eclampsia, which can be a very serious complication of pregnancy, and which is potentially deadly to both mother and baby. Their hearts were in the right place, but their methods were ill-considered and extreme.
Furthermore, the safety of this approach had not been established before it was adopted, as is unfortunately common in obstetrics. (Think of all the babies damaged when their mothers' doctors prescribed DES.)
Unforseen Consequences: Underweight Babies
What they found out later was that these extreme approaches actually CAUSED more harm then they averted. Many babies were born too small or very stressed; some no doubt died as a result of these interventions.
We also know that babies born underweight or "small-for-gestational age" (SGA) have more health problems later in life so the consequences of restricted fetal growth go far beyond problems at birth.
This is why the Institue of Medicine (IOM) adopted new weight gain guidelines in 1990, raising the recommended weight gains in pregnancy. They noted years of research that showed that low weight-gain in pregnancy caused an increase in SGA babies....in women of all sizes.
They also noted that in the 70s, when weight gain restrictions began easing up, there was a strong reduction in the occurrence of SGA babies.
So they raised the guidelines, and then began the big job of trying to get doctors to believe in this new system of weight gain guidelines. It was a difficult job.
Current IOM Weight Gain Guidelines
The old weight gain recommendations vary by source and by decade to some extent, but generally they fell somewhere between 10-20 lbs. By the 1970s, several organizations set a desirable range of around 20-25 lbs. or so.
The IOM raised these guidelines...but not across the board. They differentiated weight gain recommendations by BMI. Their guidelines were:
- "Underweight" women: 28 - 40 lb. weight gain
- "Normal" Weight women: 25 - 35 lb. weight gain
- "Overweight" women: 15 - 25 lb. weight gain
- "Obese" women: at least 15 lb. weight gain
The reason they had different weight goals by BMI was because weight gain's effect on fetal size varies by pre-pregnancy BMI.
The highest risk for SGA babies was in underweight women who didn't gain enough weight in pregnancy. Research clearly shows that gaining more weight can prevent many SGA babies in this group, so they raised the upper limit in this group to 40 lbs.
The effect of greater weight gain in preventing SGA babies is less pronounced as maternal size goes up; thus they felt that smaller gains were justifiable in the other groups. Still, women of "normal" size were now allowed to gain up to 35 lbs., which was a little more lenient than in the past.
The effect of weight gain on SGA babies is least strong in overweight and obese women, so therefore they felt only a small weight gain was appropriate in this group.
However, they did note that very small weight gains/losses caused increases in SGA babies across the board, even in obese women, and therefore they were not comfortable in recommending <15>This has been very controversial; many doctors still believed that obese women should gain little or nothing in pregnancy. They believed a larger gain in fat women would lead to a stronger risk of....ta da!!....pre-eclampsia. And big babies. And cesareans. And would result in more obesity after the pregnancy because of retained weight. So they've been chafing under these "guidelines" ever since.
Pressure to Revise the Weight Gain Guidelines
This chafing over guidelines has reached fever pitch now as a result of the obesity hysteridemic. More and more are pressing for lower weight gain goals.
Recently, a number of doctors have banded together to pressure the IOM to revise its guidelines on weight gain in pregnancy, and in particular to lower the guidelines for obese women.
They are hawking the same old concept again, namely: Large women have a higher risk for pre-eclampsia and big babies, so if we prevent a large weight gain in them, we'll lower the risk for pre-eclampsia and get smaller babies!! And prevent further obesity afterwards!!
Know what guidelines they are proposing for obese women?
- Class I obese women (BMI 30-34.9): 10 - 25 lbs. gain
- Class II obese women (BMI 35-39.9): 0 - 9 lbs. gain
- Class III obese women (BMI >40): 0 - 9 lbs. loss
Alas, their P.R. campaign is working; the IOM has begun meetings to discuss revising weight gain guidelines again.
Coming Soon: Deconstructing the research being used to justify lowering these cutoffs.