Prenatal monitoring
Week-by-Week Weight Gain Guide
Weight gain varies by BMI, metabolism, and fetal growth. Use this week-by-week reference to discuss trends with your prenatal care team. Values reflect Institute of Medicine guidelines for singleton and twin pregnancies.
| Gestational weeks | Singleton gain (cumulative) | Twin gain (cumulative) | Notes |
|---|---|---|---|
| 1–4 | 0 – 0.5 kg | 0 – 0.7 kg | Implantation and early symptoms; minimal gain expected. |
| 5–8 | 0.5 – 1.5 kg | 0.7 – 1.8 kg | Breast changes, increased blood volume. Manage nausea/hydration. |
| 9–12 | 1 – 2 kg | 1.4 – 2.5 kg | Finish first trimester. Ultrasound dating recommended. |
| 13–16 | 2 – 3 kg | 2.8 – 4.1 kg | Appetite improves; focus on balanced meals and prenatal vitamins. |
| 17–20 | 3.5 – 5 kg | 4.5 – 6.3 kg | Anatomy scan window. Protein and iron needs increase. |
| 21–24 | 5 – 6.5 kg | 6.8 – 8.6 kg | Monitor for gestational diabetes. Maintain consistent activity. |
| 25–28 | 6.5 – 8 kg | 8.6 – 11.3 kg | Support posture and core strength. Watch for edema. |
| 29–32 | 8 – 9.5 kg | 11.3 – 13.6 kg | Growth accelerates. Ensure adequate hydration and fiber. |
| 33–36 | 9 – 11 kg | 13.6 – 15.9 kg | Finalize birth plan. Balance rest and gentle movement. |
| 37–40 | 10 – 13.6 kg | 15.9 – 19 kg | Term pregnancy. Frequent prenatal visits monitor blood pressure and fetal position. |
How to Use This Guide
- Compare your cumulative gain to these ranges; minor deviations are normal.
- Discuss significant shifts with your provider to evaluate nutrition, metabolic health, or fluid retention.
- Pair with regular prenatal visits, glucose testing, and blood pressure monitoring.
Formula
Cumulative gain = Current weight − Pre-pregnancy weight
Weekly gain (2nd/3rd trimester) ≈ (Cumulative gain − First trimester gain) ÷ Weeks since week 13
Use BMI-adjusted targets to personalize ranges (see BMI calculators provided elsewhere in this app).
Full Description
Most weight gain occurs in the second and third trimesters as blood volume, amniotic fluid, placenta, and fetal mass increase. Steady, moderate gain supports fetal growth and postpartum recovery. Twin pregnancies require higher caloric intake and more frequent monitoring; aim for earlier gains to support dual growth.
Recognize that morning sickness, hyperemesis, edema, and metabolic conditions impact weight trends. Collaborate with your obstetric provider, dietitian, and possibly maternal-fetal medicine specialist to tailor nutrition and activity plans.
Frequently Asked Questions
What if I lose weight in the first trimester?
Mild loss from nausea is common. Focus on hydration, small frequent meals, and contact your provider if you can’t keep fluids down.
How can I monitor weight safely?
Weigh weekly at the same time of day, wearing similar clothing, and record trends to discuss at prenatal visits.
Does exercise affect weight gain?
Prenatal-approved exercise supports healthy gain, reduces back pain, and boosts mood. Follow your provider’s recommendations.
When should I worry about rapid gain?
Rapid gain accompanied by swelling, headaches, or vision changes may signal preeclampsia. Seek immediate medical advice.