According to the 2003 edition of “Journal of Midwifery & Women’s Health,” most women need to gain 25 to 35 lbs. during pregnancy. They are, after all, eating for two during the time of pregnancy. Women who are thin may need to gain more weight, and women who are overweight may need to gain less. The weight gain for pregnant moms enables the pre-birth baby to get needed nutrients, and as the pregnancy proceeds, the pre-born baby’s weight grows.
8 to 20 Weeks
From the eighth week of pregnancy to the 20th week, the baby goes from a weight of 0.4 oz. to 10.58 oz., still less than 1 lb. The average weight of the unborn baby progresses as follows: week 9 at 0.07 oz., week 10 at 0.14 oz., week 11 at 0.25 oz., week 12 at 0.49 oz., week 13 at 0.81 oz., week 14 at 1.52 oz., week 15 at 2.47 oz., week 16 at 3.53 oz., week 17 at 4.94 oz., week 18 at 6.70 oz. and week 19 at 8.47 oz. The baby’s length during this time is measured from the crown to the rump because the legs are curled up during this time and difficult to measure. The baby’s length progresses from 0.63 inch in the eighth week to 6.46 inches during the 20th week.
20 to 42 Weeks
The manner in which the baby’s length is measured changes at the 20th week, when it begins to be measured from crown to heel. This length progresses from 10.08 inches during the 20th week to 20.28 inches in the 42nd week. The baby’s weight progresses from 10.58 lbs. during the 20th week to 8.12 lbs. during the 42nd week. The average weight progresses as follows: week 21 at 12.70 oz., week 22 at 15.17 oz., week 23 at 1.10 lb., week 24 at 1.32 lb., week 25 at 1.46 lb. and week 26 at 1.68 lb. After week 26, the pre-born baby gains approximately 0.25 to 0.50 lb. per week through the 42nd week of pregnancy.
Mother’s Weight Gain
The MayoClinic.com warns that weight gain during pregnancy is inevitable and notes that the needed weight gain depends on a number of factors, including the pre-pregnancy weight of the mother. However, just because weight gain is inevitable, this should not be seen as a license to double the number of calories consumed simply because the mother is eating for two.