Why is weight gain important during pregnancy?
Weight gain during pregnancy is a natural and necessary process that supports the healthy development of the baby and prepares the mother's body for childbirth and lactation. Adequate weight gain is essential for providing the necessary nutrients and energy reserves to support the growing fetus. It also helps in the formation of the placenta and amniotic fluid, which are crucial for the baby's growth and development.
How does the maternity weight gain calculator work?
A Maternity Weight Gain Calculator utilizes a formula based on guidelines provided by healthcare professionals and organizations to estimate the appropriate weight gain during pregnancy. By inputting relevant data such as pre-pregnancy weight, height, age, and current gestational age, the calculator generates a personalised recommendation for weight gain throughout each trimester. This allows expectant mothers to monitor their progress and make any necessary adjustments to ensure they are on track for a healthy pregnancy.
Pregnancy weight gain by week and by trimester
During pregnancy, the ideal weight gain differs from that of non-pregnant women—and it’s not a one-size-fits-all number. Wondering how much weight you should gain? It actually depends on two key factors: your pre-pregnancy Body Mass Index (BMI) and whether you're expecting one baby or twins.
Here’s a general guide:
- Underweight (BMI < 18.5): Aim to gain 28–40 pounds.
- Normal weight (BMI 18.5–24.9): Recommended gain is 25–35 pounds, or 37–54 pounds if you’re having twins.
- Overweight (BMI 25–29.9): A healthy gain would be 15–25 pounds, or 31–50 pounds for twin pregnancies.
- Obese (BMI 30 or higher): Target weight gain is 11–20 pounds, or 25–42 pounds if carrying twins.
These numbers represent total weight gain by the 40th week. But it’s equally important to track how your weight changes throughout each trimester. According to guidelines from the Institute of Medicine, most women gain only 3–4 pounds in the first trimester due to a tiny baby size and possible morning sickness. The second trimester sees the most weight gain, while in the third trimester, gains continue but may slow down—especially in the final month.
Possible complications of sub-optimal weight gain
Sub-optimal weight gain during pregnancy—whether too much or too little—can lead to serious complications for both the mother and baby. Maintaining a healthy weight range is essential for a smooth pregnancy and healthy birth outcome. Below are key risks associated with inadequate or excessive weight gain:
- Gestational Diabetes: Gaining too much weight can raise the risk of gestational diabetes, a condition that causes high blood sugar levels and may lead to complications during and after pregnancy.
- Pre-eclampsia: Insufficient weight gain may increase the likelihood of pre-eclampsia, a pregnancy-induced high blood pressure condition that can endanger both maternal and fetal health.
- Preterm Birth: Not gaining enough weight can elevate the risk of delivering the baby before 37 weeks, which may cause complications like respiratory issues, infections, and developmental delays.
- Low Birth Weight: Inadequate maternal weight gain can result in low birth weight (under 5 pounds, 8 ounces), increasing the risk of infection, poor growth, and long-term health concerns for the baby.
- Fetal Macrosomia: Excessive weight gain may lead to a larger-than-average baby, known as fetal macrosomia, which can complicate delivery and raise the risk of shoulder dystocia and cesarean birth.
Monitoring and managing pregnancy weight gain under medical supervision can help reduce these risks and support a healthier pregnancy outcome.
What to take and what to avoid during pregnancy
Maintaining a well-balanced and nutritious diet during pregnancy is vital—not only to support the growth and development of the baby but also to protect the mother’s health. Here’s a guide to what you should include in your diet and what you need to avoid to ensure a safe and healthy pregnancy.
What to eat during pregnancy
A nutrient-rich diet builds a strong foundation for your baby’s development and keeps common pregnancy concerns like fatigue, constipation, and anaemia at bay.
1. Fruits and Vegetables
Aim for at least five servings a day in a variety of colours. They provide essential vitamins (like vitamin C and folate), minerals, and fibre to aid digestion and boost immunity.
2. Whole Grains
Opt for brown rice, oats, quinoa, and whole wheat bread. These are rich in complex carbohydrates and fibre, providing long-lasting energy and supporting digestion.
3. Lean Proteins
Include poultry, fish, eggs, legumes, nuts, and tofu. Protein is critical for fetal tissue development and helps maintain muscle strength for the mother.
4. Dairy Products
Low-fat milk, yoghurt, and cheese supply calcium, vitamin D, and protein—crucial for your baby’s bone development.
5. Iron-Rich Foods
Incorporate foods like spinach, lentils, lean red meat, and iron-fortified cereals. Iron supports the increase in blood volume and prevents pregnancy-related anaemia.
6. Plenty of Fluids
Stay hydrated with water, herbal teas, and clear soups. Hydration helps with nutrient transport, temperature regulation, and preventing UTIs—common during pregnancy.
What to avoid during pregnancy
Some foods and drinks may pose risks to the baby or lead to complications, so it's best to avoid or limit them.
1. High-Mercury Seafood
Avoid shark, swordfish, king mackerel, and tilefish. Instead, choose safer options like salmon, shrimp, and sardines which are rich in omega-3s and lower in mercury.
2. Raw or Undercooked Foods
Avoid sushi, rare meats, runny eggs, and unpasteurised dairy to prevent bacterial infections like Listeria or Salmonella.
3. Deli Meats & Soft Cheeses
Unless reheated until steaming hot, deli meats and soft cheeses (like feta, brie, and blue cheese) can harbor Listeria. Always check for pasteurised versions.
4. Excessive Caffeine
Limit caffeine to under 200 mg/day—roughly one 12-oz cup of coffee. Too much caffeine has been linked to miscarriage and low birth weight.
5. Alcohol
There is no known safe amount of alcohol during pregnancy. It can lead to fetal alcohol syndrome and long-term developmental issues.
6. Certain Artificial Sweeteners
Limit intake of saccharin and aspartame. Safer alternatives include stevia and erythritol, but consult your doctor for personalised guidance.
7. Unwashed Produce
Always wash fruits and vegetables thoroughly to eliminate pesticide residue or harmful bacteria that can pose risks during pregnancy.
Why do you gain weight during pregnancy?
Pregnancy brings about many changes—not just in your daily habits like diet and exercise, but also in how your body adapts to nurture your growing baby. These transformations begin early on and become increasingly noticeable as the weeks go by. One of the most visible changes? Weight gain.
In fact, most women gain more weight during the second and third trimesters than in the first. This increase isn’t just about the baby—it’s your body’s way of preparing for a healthy pregnancy and a smooth postpartum recovery. You can even track your personal progress with our [pregnancy weight gain calculator], which follows the medically recommended timeline.
Weight gain during pregnancy isn’t random. It happens for specific reasons and across different parts of the body:
- The baby: Naturally, a major portion of the weight gain comes from the growing fetus.
- Breast growth: Your breasts enlarge in preparation for breastfeeding—this also adds to the total weight.
- Fat storage: Your body stores extra fat to build energy reserves for both pregnancy and lactation.
- Uterus and placenta: As the uterus expands and the placenta develops to support your baby, these too add weight.
- Amniotic fluid: This protective fluid surrounding your baby contributes to the total gain.
- Blood volume and body fluids: Your body increases its blood supply and fluids to support the baby’s needs and ensure efficient nutrient transport.
Each of these elements plays a vital role in creating a supportive environment for the baby while also preparing your body for labour, delivery, and breastfeeding. So if the numbers on the scale go up, know that it’s all part of a well-coordinated biological plan designed to keep you and your baby healthy.
Factors influencing weight gain during pregnancy
Several factors influence weight gain during pregnancy, including genetics, pre-pregnancy weight, age, and lifestyle factors such as diet and physical activity. While some weight gain is inevitable and necessary for a healthy pregnancy, excessive weight gain can increase the risk of complications such as gestational diabetes, hypertension, and cesarean delivery. It is essential to strike a balance and aim for gradual and steady weight gain throughout pregnancy.
You can also check out the BMI Calculator.
