Just how much weight gain is normal in pregnancy? We know the baby, placenta and fluid around the baby comes to about 5 Kg (11 lbs) but the mom also has a bigger blood volume, lays down some more fat stores and may carry excess fluid. The Institute of Medicine in the US released suggestions for weight gain in pregnancy in May 2009 and Health Canada are using much the same. I find it easiest to plot the weight gain on a page over the course of the pregnancy. You can down load the sheet I created based on the IOM recommendations as a PDF file, found under charting, just print it in landscape format and use it yourself.
First thing to notice is that what is suggested for weight gain depends on how heavy one is at the start. The heavier one is the less weight gain is expected in pregnancy. The body mass index is the standard measure of how heavy one is, you can calculate your own at http://www.nhlbisupport.com/bmi/bmi-m.htm once you know your weight and height (the formula is wt in kg divided by the height in meters squared).
If you are at normal weight for your height, a BMI of 18.5 to 24.9 -, the solid line on the chart – we expect only about 1.5 Kg (just over 3 lbs) up to 12 weeks but by the end of pregnancy we expect a weight gain of 13.5 Kg (30 lbs or 2 stone 2 lbs). If you are thin, BMI under 18.5, – the dotted line on the sheet – then by the end of pregnancy we expect a total of 15.7 Kg (35 lbs or 2 stone 7lbs) . If you were overweight to start with, BMI 25 – 29.9, – short dashed line, then we expect only 9 Kg weight gain over the pregnancy (20 lbs or 1 stone 6 lbs). If you were heavy to start with, BMI over 30, – long dashed line – then we expect only 7 Kg weight gain over the pregnancy (15.5 lbs or 1 stone 1.5 lbs).
Too much weight gain predisposes one to gestational diabetes. It is also associated with a larger baby. Also after birth it may be more difficult to get back to a healthy weight. Too little weight gain may also not be good but likely is less of a concern especially if one is overweight at the start of the pregnancy.