Pregnancy Weight Gain: How Many Kilos, and How to Manage It

“You're eating for two now.” You hear it at every family meal, along with a second helping of pastilla or a plate of chebakia (honey-soaked sesame pastries). Yet pregnancy weight gain follows fairly precise guidelines, which depend mainly on your weight before you became pregnant. Knowing them helps you avoid two traps: feeling guilty about every kilo, or letting things slide without noticing.

The UK's NHS says most women gain between 10 and 12.5 kg, mostly after week 20. But the right range for you is something you can work out.

How much weight should you gain during pregnancy?

The international reference is still the one from the US Institute of Medicine, published in 2009 and adopted by American obstetricians and gynaecologists. In France, the High Council for Public Health endorsed it in an opinion in January 2022, La Revue du Praticien reports. It is based on your body mass index (BMI) before pregnancy:

In the first trimester, a total gain of 0.5 to 2 kg is expected. For a twin pregnancy the ranges are higher, for example 16.8 to 24.5 kg for a normal weight: your care team will guide you, and our article on carrying twins explains that follow-up in detail.

How do you calculate your BMI?

Divide your pre-pregnancy weight (in kilos) by your height (in metres) squared. Example: 62 kg for 1.62 m gives 62 ÷ (1.62 × 1.62) = 23.6. You are in the “normal weight” category, so the 11.5 to 16 kg range applies to you.

Why do you put on weight during pregnancy?

Because your body is building. A good share of the weight is the growing baby and everything around it: placenta, amniotic fluid, a larger uterus and increased blood volume. The rest, according to the NHS, is fat stores your body lays down to produce milk after the birth.

That is why gaining too little is not good news. The NHS links it to a risk of premature birth and low birth weight, meaning under 2.5 kg.

On the other hand, gaining too much increases the risk of gestational diabetes, high blood pressure, premature birth, caesarean section and blood clots in the veins, according to Santé publique France. Screening for diabetes and how it is managed are explained in our article on gestational diabetes.

Can you diet while pregnant?

No. Santé publique France is clear: all weight-loss diets are contraindicated during pregnancy and while breastfeeding. The NHS adds that dieting may harm your baby. Even if you are overweight or obese, the aim is not to lose weight but to gain less, and steadily.

If your BMI was over 30 or under 18.5 before pregnancy, your doctor or midwife can offer you dietary follow-up from the start. Ask for it if nobody mentions it.

“Eating for two”: what you really need

You will probably feel hungrier, the NHS acknowledges, but you do not need to eat for two, even if you are expecting twins. Santé publique France puts it another way: you do not have to eat twice as much. What counts is quality:

• a proper breakfast, which cuts down on sugary snacking during the morning;
• vegetables at every meal, and pulses (lentils, chickpeas, loubia, Moroccan white bean stew) several times a week;
• simple snacks if hunger gnaws at you: a piece of fruit, a plain yoghurt, a handful of almonds, a few dates, a slice of wholemeal bread with cheese;
• water rather than juices and fizzy drinks.

For details of which foods to favour and which to avoid, see our guide to eating well when you're pregnant.

The Moroccan traps behind extra kilos

It is not everyday tagines that push the scales up, but the extras that pile up:

• Pastries and sweet tea. Gazelle horns, chebakia, sellou, msemen with honey, several glasses of very sweet tea a day: these treats come back at every visit, every celebration, every sbou3 (the naming ceremony held seven days after a birth). Have a taste, without making it a daily habit.
• “Homemade” juices. Orange juice, panaché (mixed fruit juice), avocado shakes: they are often very sweet and not very filling. Whole fruit is better.
• Unlimited bread. It comes with everything; keep to a reasonable portion and choose wholemeal or barley bread.
• Ramadan. If you fast with your doctor's agreement, the risk is making up for it with a very rich f'tour (the meal that breaks the fast) and shour (the pre-dawn meal). Our article on Ramadan during pregnancy helps you decide and get organised.
• Family who insist. A simple, smiling answer (“the midwife is keeping an eye on my weight”) is better than a plate you feel forced to finish.

Staying active helps manage your weight too

France's National Authority for Health (HAS) lists preventing excessive weight gain among the benefits of physical activity during pregnancy. If there are no complications, it recommends 150 to 180 minutes of endurance activity a week, over at least three sessions: brisk walking, swimming or an exercise bike. The NHS advises keeping up your usual activity unless you are told otherwise. Ideas and precautions are in our article on exercise during pregnancy.

Sudden weight gain: when should you get checked?

A rapid increase over a few days, especially if your rings no longer fit and your face is puffy, is not “greed”. Sudden swelling of the face, hands or feet is one of the signs of pre-eclampsia, along with headaches and vision problems. Quebec's INSPQ lists swelling that becomes widespread among the warning signs in pregnancy. Everything is explained in our article on pre-eclampsia.

The weight gained during pregnancy does not vanish in a week, and that is not the goal. After the birth, part of it goes quickly and the rest over the following months, all the more easily if your gain stayed within your range.