Protein and Pregnancy: The Guide for Active Women
If you're pregnant and still training, you're navigating a gap that standard prenatal nutrition advice rarely fills. Most guidelines are built around sedentary or lightly active women. When you add consistent workouts to the equation, your energy and protein needs shift significantly, and the margin for error shrinks.
A large-scale study published in PLOS Medicine has given clinicians and active women alike a clearer picture of what adequate prenatal nutrition actually does. The findings are worth understanding, not just as abstract science, but as a practical framework you can apply right now.
What the PLOS Medicine Research Actually Found
The study examined the effects of balanced energy and protein (BEP) supplementation across multiple low- and middle-income countries. The core finding: when pregnant women consistently met both their caloric and protein targets, birth weight outcomes improved meaningfully. The effect was not marginal.
Critically, the research showed that protein alone wasn't the driver. It was the combination of adequate energy and adequate protein that moved outcomes. This distinction matters. A woman who hits her protein targets while running a caloric deficit is not in the same position as one who meets both. The body doesn't prioritize fetal development when it's short on fuel.
While the study population was drawn from lower-resource settings, the underlying physiology is universal. Protein synthesis, fetal growth, and placental function don't operate differently based on geography. The BEP principle applies to any pregnant woman whose intake is falling short of her actual demands.
Why Active Women Are Particularly at Risk of Falling Short
Standard prenatal energy recommendations typically add around 300 to 450 calories per day above pre-pregnancy baselines, depending on the trimester. That figure is calibrated for women who are largely sedentary. If you're running three days a week, lifting twice, or maintaining any structured training program, those numbers underestimate your real needs.
Exercise increases total daily energy expenditure. During pregnancy, the body is already managing an elevated metabolic baseline to support fetal growth, placental function, increased blood volume, and tissue expansion. Layer training on top of that and the gap between standard advice and actual need widens further.
Many active women also tend to be nutrition-conscious in ways that can backfire during pregnancy. Habits like limiting carbohydrates, eating in smaller windows, or keeping calories tighter than needed may feel disciplined but can compromise the energy availability your body requires to support both performance and fetal development simultaneously.
Translating BEP to Real Food
The supplementation used in the BEP research isn't the point. The point is the principle it embodies: calories and protein both need to be deliberately and consistently met. You don't need a specialized supplement to achieve this. A food-first approach works for most active women with normal pregnancies.
Here's what that looks like in practice:
- Fatty fish (salmon, sardines, mackerel): Delivers high-quality protein alongside DHA, an omega-3 fatty acid with direct relevance to fetal brain development. Two to three servings per week covers your bases without approaching the mercury thresholds to be mindful of.
- Eggs: One of the most complete single-ingredient protein sources available. They're also rich in choline, which supports neural tube development and is often absent from standard prenatal vitamins.
- Legumes (lentils, black beans, chickpeas): Contribute plant-based protein, folate, iron, and fiber. Combining them with a small amount of animal protein or vitamin C-rich foods improves iron absorption.
- Full-fat dairy (Greek yogurt, cottage cheese, whole milk): Provides protein, calcium, and iodine, a nutrient many women underconsume during pregnancy despite its role in thyroid function and fetal brain development.
- Lean meats and poultry: Efficient protein delivery with high bioavailability, plus heme iron, which the body absorbs more readily than the non-heme iron in plant sources.
If budget is a consideration, protein sources that actually work for athletes at lower cost include eggs, canned fish, lentils, and cottage cheese. These are among the highest-value options whether you're pregnant or not.
Protein Targets: What the Numbers Look Like
The general recommendation for protein during pregnancy sits around 1.1 grams per kilogram of body weight per day, based on guidelines from the Institute of Medicine. However, several sports nutrition bodies and registered dietitians working with active populations suggest that figure is conservative for women maintaining moderate to high training loads.
A more practical target for an active pregnant woman may sit closer to 1.5 to 1.8 grams per kilogram of body weight, particularly in the second and third trimesters when fetal protein accretion accelerates. That translates to roughly 100 to 130 grams of protein per day for a 70-kilogram woman. These figures should be individualized, which is exactly why working with a professional matters.
Timing also plays a role. Distributing protein intake across three to four meals rather than loading it into one or two sittings improves muscle protein synthesis and helps manage the nausea and early satiety many women experience in the first trimester. For more on structuring intake around your sessions, timing your meals around workouts covers the core principles that apply whether you're pregnant or not.
Energy Availability: The Variable Most Women Underestimate
Energy availability is the amount of dietary energy left over for physiological function after accounting for exercise energy expenditure. In athletic populations, low energy availability is associated with hormonal disruption, bone stress, and suppressed immune function. During pregnancy, chronically low energy availability adds fetal growth restriction to that list of risks.
You don't need to track every calorie with precision. But if you're training consistently and noticing signs like persistent fatigue beyond normal first-trimester tiredness, poor recovery, or difficulty maintaining training load, energy intake deserves a serious look before attributing everything to pregnancy itself.
The research on anti-inflammatory nutrition is also relevant here. Chronic training stress combined with the inflammatory demands of pregnancy can strain recovery if diet isn't supporting it. what the evidence shows on anti-inflammatory foods for athletes is worth reviewing as a complementary layer to your protein and calorie strategy.
Supplements: Where They Fit and Where They Don't
A quality prenatal multivitamin covers the micronutrient baseline. Folate (or methylfolate for better absorption), iodine, iron, and vitamin D are the priority nutrients that food alone may not reliably deliver in adequate amounts during pregnancy.
Protein supplements are a legitimate tool when food intake is genuinely difficult, particularly in early pregnancy when nausea limits what you can eat. A plain whey or pea protein powder with minimal additives can help bridge gaps without requiring a full meal. That said, supplements are not a substitute for a diet built around whole foods, and the supplement research landscape is complicated enough that understanding why supplement research is often misleading will help you make smarter decisions about what's actually worth taking.
Beyond the standard prenatal and a possible protein supplement, most active pregnant women don't need an elaborate stack. Creatine and high-dose caffeine, two common training supplements, are areas where evidence during pregnancy is insufficient to recommend continued use. Err on the side of caution and discuss anything beyond basics with your obstetric provider.
When to Involve a Professional
If you're maintaining a moderate to high training load through pregnancy, a one-size-fits-all approach to nutrition won't serve you. A registered dietitian with sports nutrition experience, or a certified sports dietitian, can calculate your actual energy and protein needs based on your body weight, training volume, trimester, and health history.
This is particularly relevant for women who were highly competitive athletes before pregnancy, those carrying multiples, women with a history of disordered eating, or anyone who has experienced poor fetal growth outcomes in a previous pregnancy.
It's also worth noting that the physical demands of pregnancy-compatible training change across trimesters. The nutrition strategy that serves you well at 14 weeks may need adjustment at 28 weeks. Regular check-ins with a qualified professional, rather than a single consultation, will track better with what your body actually needs across each stage.
The broader point from the PLOS Medicine research is straightforward: nutrition during pregnancy has measurable consequences for outcomes, and those consequences aren't reserved for women in resource-limited settings. If you're active, your demands are higher than average. Meeting both your energy and protein targets, consistently and deliberately, is one of the most evidence-backed actions you can take for yourself and your baby.