Written by:

Dr Diane Farrar

RM, BSc health science, BSc psychology, PhD reproductive endocrinology

Dr Diane Farrar is a practising midwife with over 25 years’ experience; her clinical experience has been mostly spent on the labour ward. Her primary position is as a senior Research Fellow at the Bradford Institute for Health Research, she is also a visiting Associate Professor at the University of Leeds and visiting Research Fellow at the University of York. Diane is lead for the Reproductive and Childbirth, Clinical Research Network team at the Bradford Women’s and Newborn unit. Diane’s research interests include gestational diabetes, blood pressure changes and hypertensive disorder in pregnancy and obesity.

Pre-conception care for women who are overweight or obese

In this article:

  • The importance of pre-pregnancy lifestyle and health
  • How can a woman tell if she is overweight?
  • Can being overweight affect a woman’s fertility?
  • Losing weight in preparation for pregnancy
  • Are there any nutritional supplements recommended for obese women wishing to become pregnant?
  • Is weight loss surgery a suitable option?
  • Main points

Pre-conception care for women who are overweight or obese

The importance of pre-pregnancy lifestyle and health

Eating a well-balanced diet, exercising and maintaining a healthy weight throughout life gives the best chance of avoiding ill-health and many conditions, including cancer, heart disease and diabetes. For women, being in the best possible health before pregnancy gives them the best chance of becoming pregnant, having a successful pregnancy and a healthy infant. As men supply half the genetic material needed for a baby it is important that fathers are in good condition before conception too (healthy weight, not smoking and limiting alcohol consumption). But of course the influence of a woman’s health on her infant is greater because it is the woman that carries the baby for nine months.

There are many aspects to ‘being healthy’ — for example, eating well, being active and avoiding hazardous substances such as tobacco and alcohol — but a healthy weight should always be a priority; overweight or obese women have a greater chance of experiencing a pregnancy complication. However, it is important to remember that the chance of weight-related complications is relatively small and that most women who are overweight or obese will have no problems at all during pregnancy.

How can a woman tell if she is overweight?

Calculating body mass index is the most common way of finding out whether a person is within the healthy weight range or is underweight or overweight. Body mass index (BMI) is a measure of weight and height, so there is a mathematical calculation: divide weight in kilograms (kg) by height in metres (m) and then divide the answer by height again to get BMI.

The World Health Organization has provided categories to describe different levels of weight for all people

BMIClassification
less than 18.5Underweight
18.5 – 24.9Normal weight
25 – 29.9Overweight
30 – 34.9Class I obese
35 – 39.9Class II obese
40 upwardsClass III obese

Can being overweight affect a woman’s fertility?

Yes, being overweight or obese can affect menstrual periods, and this may reduce a woman’s chance of becoming pregnant. Being overweight or obese can have a damaging effect on the regulation of the hormones needed to become pregnant to the extent that ovulation may be reduced or even stop. Furthermore, being obese is linked to a condition called polycystic ovary syndrome (PCOS), which is linked to hormonal imbalances and infertility.

The positive news is that weight loss, even modest weight loss (5% to 10% of total body weight), can encourage normal hormone levels and a regular menstrual cycle, and that this can reverse infertility. As such, it is worth considering whether your menstrual cycle is regular (usually every 28 to 31 days) if you are having problems getting pregnant. If you are overweight then losing some or all of the excess weight may help regulate your menstrual cycle, making pregnancy more likely.

See more on obesity and fertility.

Losing weight in preparation for pregnancy

Being in the best possible shape before pregnancy is critical to the chances of conception and healthy pregnancy, especially if you retain any extra weight you gained during a previous pregnancy. Research shows that reducing weight before pregnancy reduces the chance of stillbirth, medical complications in pregnancy including gestational diabetes and macrosomia (a large baby). If you had a caesarean section in your last pregnancy, you are also more likely to achieve a vaginal birth (if this is your wish) in your next pregnancy if you can optimise your weight beforehand.

A healthy diet

This is advisable whether you are maintaining or trying to lose weight. A healthy diet is a balanced diet with limited processed foods. Processed foods are foods that are high in fat and sugar, such as fast foods (pizza/sausages) and pre-prepared convenience foods. Fruit and vegetables should make up a third of food eaten during each day; starchy foods such as bread and potatoes should make up another third; beans, pulses, fish and meat should make up around a sixth; and, lastly, oils, butter and treats such as biscuits and sweets should make up the remainder (although this last group can be reduced, especially if weight loss is desired). It is also good to drink around two litres of water each day, as this may help prevent overeating — thirst can be mistaken for hunger. Eating regular small meals may also help prevent overeating.

Should I cut down on the amount I eat?

The number of calories you need to consume (or cut back on) each day to lose weight will depend on your weight and how much you would like to lose and over what time period. It is important that weight loss is gradual (0.5 to 2lb per week) and that you receive all the nutrients you need each day. Your general practitioner or weight loss programme leader will be able to advise you.

Join together to lose weight

Weight loss programmes that include a support element are the most likely to be successful, so if you want to lose weight, joining a group programme or working to lose weight with a friend or group of friends should help you achieve your goal.

Get physical

Many people are not as active as they should be. Even if you are not trying to lose weight, it is important for your health that you get a moderate amount of exercise each day.

What is a moderate amount of physical activity? While taking up a sport or hobby that includes exercise is great, it can be hard to find time to include this alongside work and childcare. There are simple changes to everyday life, however, that will increase activity levels and fitness (and may help with weight loss). These changes may include: walking to work or getting off the bus a couple of stops earlier than usual, parking further away from work and using the stairs rather than taking the lift. Every little bit counts towards achieving a small amount of weight loss each week. If you are unsure about what physical exercise you can do or you have a medical condition that may affect your ability to exercise or be active, seek the advice of your general practitioner before you begin.

Are there any nutritional supplements recommended for obese women wishing to become pregnant?

All women are advised to take folic acid at least one month before conception and during the first three months of pregnancy. Folic acid helps to reduce the risk of a baby being born with a neural tube defect, such as spina bifida. Because women who are overweight or obese (BMI of 30 or above) are at increased risk of their baby being born with a neural tube defect they are advised to take a dose of 5 milligrams (mg) of folic acid. This is a higher dose than is available in prenatal vitamins and you will need to see your doctor or pharmacist to get this.  As well as being available as a supplement, folic acid is found in foods like leafy green vegetables, brown rice, granary bread, and breakfast cereals fortified with folic acid.

Vitamin D supplements are also recommended as obese women are more likely to be deficient in this vitamin, which plays an important role in regulating the amount of calcium and phosphate in the body.

Is weight loss surgery a suitable option?

Increasing numbers of women are undergoing weight loss surgery; there are various types of surgery including gastric bypass, gastric banding and sleeve gastrectomy. It is an effective way to lose weight and can lead to reversal of weight-related conditions such as type 2 diabetes. These are major surgeries, however, with associated risks. They can also be psychologically demanding as they enforce a drastic change in a person’s ability to eat food. As such, these surgeries are usually accompanied by counselling.

Women who have had weight loss surgery can and do become pregnant, but they are advised to delay pregnancy for 12 to 24 months so that the time of very marked weight loss has passed. It is also important to understand what type of surgery you have had, because food intake or food absorption may be affected differently and this may affect your growing baby. The pregnancy will be closely monitored as women who have had these surgeries may be at risk of having a small baby.

Read our article on pregnancy care for women who are overweight or obese.

Main points

  • Being in the best possible health before pregnancy gives women the best chance of having a successful pregnancy and a healthy infant.
  • Women who are overweight or obese have a greater chance of having a pregnancy complication than women who are at a healthy weight.
  • Calculating body mass index is the most usual way of finding out whether a person is within the healthy weight range.
  • Being overweight or obese can affect menstrual periods and therefore reduce a woman’s chances of becoming pregnant. Obesity is also linked to polycystic ovary syndrome.
  • It’s advisable to adopt a healthy balanced diet if you are trying to lose or maintain weight.
  • Drinking around two litres of water each day may help prevent overeating because thirst can be mistaken for hunger.
  • If you would like to lose weight, joining a weight loss programme with a support element can help you achieve your goal and is the likeliest to be successful.
  • There are simple changes to everyday life, such as walking to work (if possible) and using stairs instead of lifts, that will increase activity levels and fitness and may help you lose weight.
  • Overweight women who are trying to get pregnant are advised to take a higher dose of folic acid (5mg).
  • If you’ve undergone weight loss surgery should wait for 12-24 months after their surgery before trying to conceive. Your pregnancy should also be monitored closely by an obstetrician.

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