Weight - and in particular weight gain - are an important part of pregnancy. When you book in for pregnancy your midwife will weigh you. They may also ask about your weight history (whether you tend to stay the same weight, or have gained or lost weight). They will use your weight and height to calculate your Body Mass Index (BMI). BMI is not a measure of someone's overall health and cannot tell us anything specific about a person's health or wellbeing, but there is evidence that in general, pregnant people with a BMI of 30kg/m2 or more have an increased risk of developing Gestational Diabetes and some other pregnancy-related complications.
Pregnancy weight gain includes the weight of the baby, placenta and amniotic fluid, additional breast tissue and fat stores for milk production, and in the last trimester the weight of increased blood volume. All of these things are normal parts of a healthy pregnancy.
If you have a BMI of 30kg/m2 or more, you may be invited to a maternal health antenatal group, or offered an appointment with a dietitian. This will depend on where you are having your antenatal care. These sessions support people to have a healthy, positive pregnancy. They are non-judgmental and are not about weight loss.
If you find it difficult or upsetting to discuss your weight or would prefer not to know your weight or BMI please tell your team.
Every person’s body responds differently to pregnancy. It is estimated that most people who are pregnant with one baby will gain 10kg to 12.5kg (22lb to 28lb) across 40 weeks of pregnancy, most of that from 20 weeks onwards. If you have a BMI above 30kg/m2 you might be advised to try to gain less weight. If you have a BMI below 18.5kg/m2 you might be advised to try to gain more weight. If you are expecting more than one baby your team might also advise you about weight gain.
There are many reasons why people gain different amounts of weight, for example: changes in food preferences, increased or decreased appetite, nausea or vomiting, or changes in activity levels related to fatigue or pregnancy-related aches and pains such as pelvic girdle pain or low back pain.
Weight gain can impact the risk of some pregnancy-related complications. Gaining too much weight can increase the risk of developing Gestational Diabetes and high blood pressure. Not gaining enough weight can lead to premature birth or having a very small baby. Doing the best you can to eat well and have a healthy amount of pregnancy weight gain will help to reduce these risks. Attending all of your antenatal appointments means that advice can be tailored to you.
It is rare that someone would be advised not to gain weight in pregnancy. Weight gain is an important part of a healthy pregnancy.
Please speak to your team if you:
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