Weight Gain During Pregnancy: What is Optimal?

Yes, we’re going here. Weight gain is among the most sensitive topics out there when it comes to pregnancy. But because it can be a bit taboo, sometimes we’re left feeling a little unsure about what’s normal and what’s not. 

So we’re looking this one right in the eye. Just the facts without the shame or judgment. What we know (and what we don’t), why it matters (and why it doesn’t), and what we can do to optimize our whole health profile throughout pregnancy for the best chance at pregnancy outcomes for both mama and baby. 

What’s Recommended

Before we get into it, we’ll start by providing the official Institute of Medicine (IOM) weight gain recommendations. While certainly not perfect or foolproof, they provide a reasonable range of guidance to use as a starting point in determining a healthy weight gain for your unique body. These recommendations are based on your body mass index (BMI) prior to pregnancy. Your BMI is an estimation of body fat based on height and weight. You can calculate it here.

Why Weight Gain Does Matter

Weight gain does matter in pregnancy, but not necessarily for the reasons you might think. Here’s why:

Weight gain can be an indicator of baby’s growth

Weight gain can help determine if baby is growing properly. However, your weight is simply one data point and by no means a perfect indicator of your health or baby’s health. It is entirely possible for baby to grow on track if your weight gain is slow, or for baby to not grow adequately even if you gain within or above the recommended range. Baby requires nutrients, not just calories, to develop properly.

Weight gain can be a sign of other underlying health conditions

Too little or too much weight gain may be a sign of a health condition - either related or unrelated to pregnancy. For example, conditions like inflammatory bowel disease may cause malabsorption of nutrients and slow weight gain. Diabetes and thyroid disease can also impact weight gain and negatively affect pregnancy outcomes. 

If your weight gain pattern seems disconnected to your lifestyle (e.g., gaining quickly without much change in diet or appetite), or if you have sudden gain or loss of several pounds, let your practitioner know. Additional testing may be needed to rule out other conditions.

There are risks associated with too much weight gain

Studies have shown that gaining above the guidelines during pregnancy can increase the likelihood of adverse pregnancy outcomes for both the mother and baby, including higher rates of gestational diabetes, preeclampsia and gestational hypertension, postpartum hemorrhage, shoulder dystocia (shoulders get stuck during delivery), macrosomia (baby is larger than expected), and neonatal hypoglycemia (baby’s blood sugar drops too low after birth). 

One study looked at weight gain above the Institute of Medicine guidelines, and found that with excess weight gain, all BMI categories had an increased risk of hypertensive disorders. Women within a normal BMI range and an overweight BMI range also had increased risk of cesarean delivery and neonatal birth weight at or above the 90th percentile.

There are risks associated with too little weight gain

Gaining too little weight during pregnancy can increase your chances of having a preterm birth and/or a baby born at low birth weight. Both of these scenarios have implications to baby’s health that can extend beyond infancy.

Weight gain is essential

Growing another life inside of you demands a lot on the body, and it requires the body to carry additional weight. The breakdown of this weight is estimated as follows: 

  • Baby: 7-8 pounds (average)
  • Placenta: 2 pounds
  • Breast tissue (to get ready for breastfeeding): 2 pounds
  • Increased fluid volume: 4 pounds
  • Increased blood volume: 4 pounds
  • Uterus: 2 pounds
  • Maternal fat stores: 7 pounds

This totals about 30 pounds, and clearly, these things are all quite essential to creating the new life inside of you. It’s important to note that these are average numbers, and all of them can fluctuate within a healthy range. The largest fluctuation that affects overall weight gain (and not day to day swings, which are affected by fluid retention) is maternal fat stores. This number can vary quite widely due to a woman’s unique body chemistry (hormones, genetics, etc.), and of course, her diet and lifestyle. 

If a woman has a higher BMI and gains less than this amount, she’s likely gaining less fat stores, or even losing some fat stores as her body already had what it needed to support her baby and breastfeeding needs.

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Why Weight Gain Doesn’t Matter

The amount of weight you gain during pregnancy can be important, but is by no means a sole indicator of your health, your baby’s health, or your pregnancy outcomes. There are plenty of reasons to not get wrapped up in pregnancy weight gain:

Weight alone is not an indicator of health

Weight gain does not indicate how well-nourished you are, and when it comes to pregnancy, nourishment is critical. You could gain 25 pounds eating a highly processed diet that doesn’t provide you or baby with the nourishment you both need. Or you could gain 35 eating a diet rich in healthy whole foods with plenty of fat and protein. Weight, like age, in many ways, is just a number.

Weight gain recommendations aren’t foolproof

The IOM recommendations are largely based on BMI, but BMI is an estimation with known  limitations. BMI is a simple way to get a general view of your body's proportions, but it does not take body composition into account (for this you need a much more sophisticated and often expensive test). Those with a muscular body may have an overstated BMI which is not a good indicator of health. On the other hand, a person with a “normal” BMI may actually lack muscle mass and have higher than ideal visceral fat (the more dangerous fat around the organs of the abdomen). Since BMI can suggest an inaccurate picture of your health, it can also serve as an inaccurate benchmark for your “recommended” weight gain.

What is important to know

  • Weight gain isn’t linear: Many pregnancy apps will tell you to expect to gain 0.5 to 1 pound per week in the second and third trimesters, the reality is, you may go a week or two not gaining anything and then gain 2 pounds in a week. You may also gain or lose weight in the First Trimester, despite many sources sharing that your weight will likely remain steady. Any of these patterns are well within the wide range of normal. However, know that large spikes (5+ pounds in a day or two) can be concerning later in pregnancy, and warrant a call to your provider just to be sure there is nothing of concern.
  • You can be appropriately fed but undernourished: Just because you are gaining weight at a pace that feels good and healthy doesn’t mean that you are getting all of the nourishment you need. Do your best to eat a nutrient-dense diet and be sure to include high quality supplements in your routine, like our Prenatal Multi, Collagen, Pre/Probiotic, and Omega-3.
  • Your body is unique, and your pregnancy is unique: It can be hard, but try to not compare your weight gain to anybody else's, or even to a prior pregnancy. All bodies and pregnancies are different.
  • It won't all come off at once: Even if you only gained 25 pounds, don’t expect it all to come off on delivery day. While it might seem like much of the weight should be gone immediately, it takes time for the body to readjust. You’ll still be carrying weight from extra blood and fluid, your uterus and breasts are still larger (and likely full of milk now), and your body will probably hang onto some fat as a way to support lactation needs.
  • Your body needs more calories: Yes, your body needs some extra calories in pregnancy (anywhere from 200-350 additional) but don’t get too hung up on this. Unless you are struggling to gain weight, rather than counting extra calories, try to listen and respond to your body’s hunger cues. Some days you may feel much hungrier, others you may not. Follow your body’s lead.

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What you can do

So with a decent amount of gray area around pregnancy weight gain, what can you do to support the best outcome for you and your baby? Here are some tips, keeping in mind that weight is just one component of overall health:

  • Focus on nourishment not calories (with an emphasis on protein, fat, and micronutrient-rich carbs), and remember that the better you nourish yourself, the better you nourish your baby
  • Listen to your body and follow your hunger-fullness cues 
  • Honor your cravings in a way that respects your body
  • Don’t obsess over the number on the scale but have a healthy awareness of its pattern in case it is indicating something else going on with your health
  • Use the IOM recommendations as a guide not gospel (particularly if you feel your BMI is not a good reflection of your body composition)
  • Express any concerns to your provider, and if you don’t feel supported, seek another opinion
  • Be aware that the pursuit of health and a “perfect” diet or weight can quickly turn into disordered eating. Seek help from a trusted mental health practitioner if needed.

While much of the discussion around pregnancy weight gain is either polarizing or confusing, we hope this information was helpful and empowering. Because at Needed, empowering optimal health and a feel-good perinatal journey is at the core of what we do.