In recent years, weight gain during pregnancy does not seem to be emphasized as much, so I would like to talk about weight gain and weight loss.
This is my personal view:
- When I myself was conceived (in the post-war period of food shortages, the 1940s–1950s), mothers were often told, “Eat for your baby as well” for the baby’s development. Mothers of that generation made great efforts.
- Later, when my generation became pregnant during the economic bubble era (1970s–1980s), mothers told their daughters, “Eat for your baby as well”. As a result, when I became an obstetrician, I saw quite a number of patients who developed hypertensive disorders of pregnancy in the later stages of pregnancy.
- After that, it became understood that overeating during pregnancy was not good for the pregnancy. Thus dietary restrictions were introduced. As a result, the number of low-birth-weight babies began to increase.
And now, weight management is not much discussed anymore.
But does this mean we don’t need to care about weight?
In fact, weight gain is linked to increased risks of hypertensive disorders of pregnancy and gestational diabetes.
Hypertensive disorders of pregnancy
Placental function decreases, oxygen and nutrients cannot reach the baby sufficiently, leading to fetal growth restriction, placental abruption, fetal death, maternal hypertension, and serious risks to both mother and baby.
Gestational diabetes
The baby may grow into a very large infant (>4,000g), with risks including intrauterine fetal death, neonatal hypoglycemia, congenital anomalies, growth restriction, and a higher chance of cesarean delivery.
During pregnancy, there can also be low back pain, and during delivery, fat on the uterus and birth canal can prolong labor.
On the other hand, if the mother loses weight or does not gain enough weight, the baby may become a low-birth-weight infant (≤2,500g), which is linked to prematurity and higher mortality rates.
Why does a pregnant woman’s weight increase?
At delivery, weight gain is generally about 8 kg in total:
Baby : approx. 3 kg
Placenta : approx. 0.5 kg
Amniotic fluid : approx. 0.5 kg
Increased maternal blood and fluids : approx. 2 kg
Subcutaneous fat : approx. 2 kg
Appropriate Weight — Revised by the Ministry of Health, Labour and Welfare (2021)
BMI = Pre-pregnancy weight (kg) ÷ height (m) ÷ height (m)
Guidelines for Weight Gain During Each Stage of Pregnancy
After mid-pregnancy, weight gain should be limited to 300–500 g per week.
Points for Weight Management During Pregnancy
Timing of weight gain:
- During morning sickness
- After morning sickness subsides
- During home rest
- During maternity leave
- When returning to parents’ home
- At the start of the last month of pregnancy
Tips for weight management:
- Eat a well-balanced diet, with sufficient vitamins and minerals.
- Be mindful of calorie intake. If pre-pregnancy intake was 2000 kcal :
Early pregnancy : +50 kcal Mid-pregnancy : +250 kcal Late pregnancy : +450 kcal - Avoid excessive sugar : limit cakes and sweets
- Avoid excessive salt : 6.5 g/day; can cause hypertension and edema
- Engage in light exercise within safe limits : moderate walking (caution if risk of preterm labor)
For maternity aerobics, yoga, swimming : always with an instructor, never alone
Stay hydrated, but with care : 1.5–2 L per day (approx. 40 ml per kg of body weight)
Daily weight management:
- Measure weight daily at the same time; chart it if possible
- Record meals; consider using a weight management app
- Strict dieting is prohibited : it affects the baby’s nutrition
- Eat regular meals; have dinner early
- Eat slowly
- Eat plenty of vegetables, limit fried and fatty foods
- Season food lightly
- Limit caffeine: it may affect fetal development
While we’ve discussed weight management during pregnancy, it is not something to be overly anxious about. Instead, focus on daily eating habits while wishing for your baby’s healthy growth.
If you have concerns about diet or nutrition during pregnancy, please let us know so you can enjoy a comfortable pregnancy and look forward to giving birth of a healthy baby.
July, 2025
Chairperson Kazuhiro Hisamatsu