Weight gain during pregnancy is a natural and necessary process for fetal development and preparing the body for childbirth. This process is not about extra pounds, but about creating a healthy environment for the baby. To minimize risks, it is important to adhere to certain guidelines. Let’s look at the norms for weight gain, the factors that influence them, and recommendations for control.
Weight gain during pregnancy is uneven and has its own characteristics in each trimester.
Weight gain dynamics by trimester
First trimester (up to 12 weeks): Weight gain is usually minimal (up to 2 kg) or absent due to toxicosis, which is normal if you feel well.
Second trimester (13th to 27th week): Growth accelerates, with weekly weight gain of about 300 g (up to 1 kg per month).
Third trimester (from the 28th week until delivery): Weight gain is at its maximum—up to 400 g per week (about 1.2–1.5 kg per month) due to the intense growth of the fetus.
Individual norms: the role of body mass index
The key factor in determining the individual norm is a woman’s body mass index (BMI) before pregnancy.
BMI formula: weight (kg) / height (m)².
Recommended weight gain ranges depending on BMI:
- BMI < 18.5 (underweight): Recommended total weight gain is 12.5–18 kg.
- BMI 18.5–24.9 (normal weight): Optimal weight gain is 11.5–16 kg.
- BMI 25.0–29.9 (overweight): Recommended weight gain is 7–11.5 kg.
- BMI ≥ 30.0 (obese): Total weight gain is within the range of 5–9 kg.
- BMI > 40.0 (severely obese): Recommended weight gain – up to 5–7 kg.
These are average guidelines. Minor deviations are acceptable if you feel well and your doctor approves.
Features of weight gain in multiple pregnancies
In multiple pregnancies, the norms for weight gain are higher:
- With a normal BMI (18.5–24.9): 17–25 kg.
- If you are overweight (BMI 25.0–29.9): 14–23 kg.
- If you are obese (BMI ≥ 30.0): 11–19 kg.
Weight gain after IVF: are there any differences?
Pregnancy after IVF often requires closer attention to weight due to hormone therapy.
- Standard IVF: BMI recommendations remain the same, but closer monitoring is required as hormones can affect metabolism and fluid retention.
- IVF with donor eggs or double donation: Requires even stricter control. Hormonal preparation can increase weight gain and increase the risk of preeclampsia (sudden weight gain, edema). Gradual weight gain and strict medical supervision are important.
Regardless of the IVF protocol, all recommendations should be discussed with your doctor.
Structure of weight gain: physiological distribution
Weight gain (10–15 kg) is distributed not only to the fetus (3–4 kg), but also to the entire body:
- Fetus: 3000–3500 g
- Placenta: 500–800 g
- Amniotic fluid: 900–1000 g
- Uterus: 900–1200 g
- Mammary glands: about 500 g
- Circulating blood volume: 1200–1800 g
- Tissue fluid: about 2700 g
- Fat deposits (energy reserve): 2200–3000 g
The importance of weight control for the health of mother and child
Weight control is important for the health of mother and child, reducing the risk of complications:
- Gestational diabetes mellitus;
- Arterial hypertension;
- Uterine bleeding;
- Impaired placental blood flow;
- Premature birth;
- Macrosomia (large baby);
- Need for emergency C-section;
- Birth injuries.
Being underweight is also dangerous: it can lead to low birth weight, developmental delays, and premature birth.
Practical recommendations for maintaining optimal weight
- A balanced diet. Focus on high-quality foods: vegetables, whole grains, lean proteins (meat, fish), and fermented milk products.
- Frequent meals. 5-6 small meals a day stabilize blood sugar and prevent overeating, nausea, and heartburn.
- Drinking regime. Maintaining water balance is critically important (about 30 ml of water per 1 kg of weight per day).
- Meal planning. A pre-planned menu and healthy snacks help you avoid unhealthy food choices.
- Physical activity. If there are no contraindications, at least 2.5 hours of moderate exercise per week (walking, swimming).
- Non-food sources of pleasure. Pregnancy is an emotional time. Find ways to relax that are not related to food (hobbies, reading, walking).
When is it necessary to consult an endocrinologist?
Consult an endocrinologist if you are gaining weight too quickly (not related to diet), having difficulty gaining weight, or have a strong craving for sweets. This may indicate endocrine disorders (e.g., insulin resistance). The doctor will conduct an examination and adjust your plan.
Remember that every pregnancy is unique. Focus not on the numbers, but on your overall well-being and your doctor’s recommendations. At the NATIVITRO reproductive medicine clinic, you will receive full support for a healthy course of your unique pregnancy.
FAQ: Short answers to important questions
I am losing weight in the first trimester. Is this dangerous? A small loss (up to 2 kg) against the background of toxicosis is a common occurrence. If you feel fine, there is no cause for concern, but inform your doctor.
Why is BMI before pregnancy important? It is a starting point. It shows whether the body was underweight, normal weight, or overweight, which determines the recommendations for weight gain.
Can I go on a diet if I am gaining weight quickly? Absolutely not. Starving yourself will harm the baby. If you are gaining weight quickly, you should improve the quality of your diet (eliminate empty calories) rather than the quantity. Discuss this with your doctor.
Are the norms strict? No, they are guidelines. Small deviations are no cause for panic. The overall trend and how you feel, as confirmed by tests and a doctor’s examination, are more important.
What kind of exercise is safe? Walking at a moderate pace, swimming, special yoga, or water aerobics. Avoid exercises that involve a risk of falling or strain on the abdominal muscles. Always get permission from your doctor.
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