Women who are pregnant or planning to become pregnant need to take special care with what they eat and how much they weigh. Most women gain more weight than doctors recommend, and a small percentage of women gain less than the recommended amount. Either of these situations can put both the mother and baby at higher risk for adverse outcomes.
Low Body Mass Index
If you have a body mass index, or BMI, below 18.5 before you get pregnant and don't gain sufficient weight during your pregnancy you are more likely to have a baby with a low birth weight, which puts your baby at risk for other health problems. These include vision and hearing problems, trouble learning at school, mental retardation and cerebral palsy, according to a 2005 study in "Southern Medical Journal." Low birth weight children are also less likely to survive than those born at a normal weight.
High Body Mass Index
Having a BMI of 25 or above before you become pregnant can also put both you and your child at risk. If you don't gain enough weight during your pregnancy, your child could be born at a low birth weight. However, the more common problem associated with having a high BMI is having a baby that is heavier than normal. This can make a prolonged labor more likely, and a C-section necessary, as the baby may be too large to fit through the birth canal.
Considerations
Other factors besides maternal BMI before pregnancy influence the birth weight of the baby. These include how much weight you gain during the pregnancy, as well as whether you smoke. Smoking makes it more likely that you will have a baby of lower birth weight than otherwise expected.
Recommendations
Women should ideally aim to be at a healthy weight before becoming pregnant. However, if your BMI is too low or too high you should be careful to keep your weight gain during pregnancy at the recommended levels. If your BMI is less than 18.5, this means gaining between 28 and 40 pounds, according to the Mayo Clinic. If your BMI is between 18.5 and 24.9 you should gain between 25 and 35 pounds; if your BMI is between 25 and 29.9 you should gain between 15 and 25 pounds; and if your BMI is 30 or greater, you should gain between 11 and 20 pounds.
References
- "Gynecologic and Obstetric Investigation;" Impact of Maternal Anthropometry and Smoking on Neonatal Birth Weight; Thomas Laml, et al., 2000
- "Journal of Obstetrics and Gynaecology Canada;" The Effect of Gestational Weight Gain by Body Mass Index on Maternal and Neonatal Outcomes; Joan M.G. Crane, et al.; January 2009
- "PRAMS Perspectives;" Maternal Prepregnancy Body Mass Index and Pregnancy Outcomes in Utah; Laurie Baksh, et al.; 2005
- "Southern Medical Journal;" Maternal Prepregnant Body Mass Index and Weight Gain Related to Low Birth Weight in South Carolina; Thomas C. Hulsey, et al.; 2005
- Mayo Clinic: Pregnancy Weight Gain: What's Healthy?
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