Many women worry about gaining weight during pregnancy, but it’s just as important to assess your body weight and fat levels before trying to conceive. Both overweight women and women with low body fat face special challenges in becoming pregnant and sustaining a healthy pregnancy. With the help of your doctor, you can manage weight issues before, during and after pregnancy to keep you and your baby healthy.
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Are You Over or Underweight?
To determine if you are overweight or underweight, calculate your BMI. Take your height in inches and square that number. Now divide your weight in pounds by the second number, and multiply by 703. You can also calculate your BMI easily online. Doctors call a BMI of between 20 and 24 "the fertility zone," because this is the optimum level for conceiving and carrying a baby. If you fall outside this range, you may face difficulty conceiving.
Low Body Fat and Fertility
Body fat has an important role in fertility. It helps convert the male hormone androgen into the female hormone estrogen. If your body-fat levels are too low, you may not be ovulating regularly or at all. If you are underweight, or have a BMI of less than 19, the 2013 issue of "Practitioner" advises that putting on body weight will improve your chances of conception. Many underweight women do not know they have stopped ovulating because they continue to get regular periods. Adding calories to your diet by eating larger portions of healthy, nutritionally balanced meals may improve your chances of conception.
Low Body Fat and Pregnancy
Being underweight affects your ability to carry a pregnancy to term. A 2006 study published in the "British Journal of Obstetrics and Gynaecology" found that women with a BMI of 18.5 or lower are 72 percent more likely to miscarry in the first trimester than women of average weight. The American Pregnancy Association recommends that underweight women attempt to gain at least 5 to 6 pounds in the first trimester, 3 pounds more than women who are at a healthy weight before conception.
High Body Fat and Fertility
Just as low body fat can interfere with ovulation, so too can high body fat. Extra fat stores can make you insensitive to the hormone insulin and lead to overproduction of the hormone leptin. Both can result in irregular or non-existent ovulation. Losing even a little bit of weight can dramatically boost your fertility. A study in the 2012 issue of "Current Pharmaceutical Design" reports that losing just 5 percent of your body weight can kickstart ovulation.
High Body Fat and Pregnancy
Overweight and obese women face several challenges during pregnancy. If your body fat is too high, you may be at increased risk for gestational diabetes and high blood pressure, reports the July 2011 issue of "Obesity." Even if you are not obese, having a higher body fat percentage can increase your risk. Routine monitoring and tests during pregnancy can detect these changes. It may also be more difficult for doctors to hear your baby’s heartbeat and gauge the size of the baby. Finally, vaginal delivery may be more dangerous for women who are significantly overweight as they have a greater risk of post-partum hemorrhaging, according to the October 2012 issue of "BMC Pregnancy and Childbirth." While you should never diet or try to lose weight during pregnancy, making healthier food choices and avoiding excessive weight gain will benefit you and your baby.
- American Pregnancy Association: Eating for Two When Over or Under Weight
- British Journal of Obstetrics and Gynaecology: Risk Factors for First Trimester Miscarriage—Results From a UK-Population-Based Case–Control Study
- Current Pharmaceutical Design: The Role of Obesity in the Development of Polycystic Ovary Syndrome
- Practitioner: Optimising the Management of Patients With Infertility
- BMC Pregnancy and Childbirth: Maternal Obesity and Postpartum Haemorrhage After Vaginal and Caesarean Delivery Among Nulliparous Women at Term: A Retrospective Cohort Study
- Obesity: Body Adiposity and Type 2 Diabetes: Increased Risk With a High Body Fat Percentage Even Having a Normal BMI