Advice Column, Fertility, Health, Lifestyle, Pregnancy, Pregnancy & Baby

Weight, Fertility and Pregnancy

  • Paarl Dietitians
  • Category Advice Column, Fertility, Health, Lifestyle, Pregnancy, Pregnancy & Baby

Getting your body ready for baby-making isn’t only about tossing your birth control and charting your ovulation. It’s also about laying the nutritional foundation for healthy baby building. Begin your eating-well campaign even before you conceive (technically these are your first weeks of pregnancy) and you’ll be doing yourself (and your soon-to-be embryo) a favour.

Begin making healthy changes 3 months to a year before you conceive. Evidence shows that healthy nutrition and fertility is linked in both men and women.

The ultimate goal is a healthy pregnancy, and this depends upon good quality eggs and sperm. There is increasing evidence to show that diet and lifestyle can directly impact on your fertility health not only for conception but also for your baby’s development. When it comes to getting pregnant, the old adage “you are what you eat” rings true. What you eat affects everything from your blood to your cells to your hormones.


If you’re trying to get pregnant, or intend to start trying, know that weight can affect your chances of conceiving and having a healthy baby. Twelve percent of all infertility cases are a result of a woman either weighing too little or too much.

Women who are overweight or obese have less chance of getting pregnant overall. They are also more likely than women of healthy weight to take more than a year to get pregnant.

Research has shown that being underweight or being overweight and obese can lead to fertility problems by creating hormonal disturbances. The main ingredient in the body weight and fertility mix is oestrogen (a sex hormone produced in fat cells).

  • A woman with too little body fat can’t produce enough oestrogen and her reproductive cycle begins to shut down. Often causes irregular menstrual cycles and may cause ovulation to stop altogether.
  • If a woman has too much body fat, the body produces too much oestrogen and may also lead to irregular menstrual cycles and ovulation. However, even obese women with normal ovulation cycles have lower pregnancy rates than normal weight women, so ovulation isn’t the only issue.

Research indicated that weight also impacts on the success of donor egg cycles. There is good scientific evidence that obesity lowers the success rates of in vitro fertilisation (IVF). Studies have further shown lower pregnancy rates and higher miscarriage rates in obese women.

How do I know if I am a good weight for pregnancy?

One of the easiest ways to determine if you are underweight or overweight is to calculate your body mass index (BMI). 

A BMI between 19 and 24 is considered normal; less than 18.5 is considered underweight. A BMI between 25 and 29 is considered overweight and greater than 30 places you in the category of obese.

Reporting in the journal Human Reproduction, researchers documented a 4% decrease in conception odds for every point in BMI above 30. For women whose BMI was higher than 35, there was up to a 43% overall decrease in the ability to conceive.

Your BMI alone is not the only thing to watch, however. Your body fat percentage and waist circumference is also important. Bottom line: you need a certain amount of fat to conceive since body fat produce oestrogen.

Waist circumference is an indication of visceral fat (excess of body fat in the abdomen). A waist circumference >88cm in a women and >102cm in a man is associated with reduced fertility, an increased risk for insulin resistance (associated with PCOS in women) and other chronic diseases such as diabetes, heart disease and high blood pressure.

Are there fertility problems in men with obesity?

Obesity in men may be associated with changes in testosterone levels and other hormones important for reproduction. Low sperm counts and low sperm motility (movement) have been found more often in overweight and obese men than in normal-weight men.

How much weight should one lose?

Even a small 3-5% weight loss can reduce insulin resistance by 40-60% and improve fertility.

How quickly will I lose or gain weight?

Healthy weight gain or loss is regarded as 500g to 1kg per week. It is therefore gradual and one can expect that six months will be required to restore normal reproductive function and pregnancy.

IMPORTANT: Avoid going on fad diets, which can deplete your body of the nutrients it needs for pregnancy and find a weight-loss plan that works for you by talking to a registered dietitian.


If a woman is obese when falling pregnant, it increases the risk of pregnancy complications and health problems for the baby.

Obese women are at an increased risk for developing pregnancy-induced (gestational) diabetes and high blood pressure (pre-eclampsia). The risk of pre-eclampsia doubles in overweight women and triples in obese women. Overweight women have twice the risk of gestational (pregnancy-related) diabetes and obese women eight times the risk, compared with women of healthy weight.

A woman who is obese is more than twice as likely to have a miscarriage as a woman of healthy weight. Sadly, there is twice the risk that her baby will not survive.

Infants born to obese women are more likely to be large for their age and therefore have a higher chance of delivering by caesarean section. Afterwards the baby may need neonatal intensive care or have a congenital abnormality.

Recovery following birth is also more problematic and there is the increased risk of poor wound healing and possible infections.


Eating a healthy and balanced diet is crucial when preparing to conceive or you are already pregnant. A balanced diet is one that is rich in good quality protein, low in Glycaemic Index (GI), low in sugar, salt, caffeine and industrially created trans-fats (trans-fatty acids or partially hydrogenated oil).

  • Make clever Protein choices – choose lean protein.
  • Rethink refined carbs and sugar – choose low glycaemic index (GI) carbohydrates and also limit your total daily carbohydrate intake based on your specific metabolic rate. This is especially important if you suffer from polycystic ovary syndrome (PCOS).
  • Be Smart about Fats – a high-fat diet could impact fertility in both men and women. Mono-unsaturated fats (MUFA) are what we refer to as the GOOD FATS and should replace the saturated and trans fats in the diet.
  • Choose Omega-3 fats –Should you dislike fish or have difficulty eating adequate amounts of other omega-3 containing foods, you can make use of an omega 3 supplement.
  • Get Your Fruits and Vegetables – are high in anti-oxidants that protect against free radicals that damages ova, sperm and reproductive organs
  • Choose Iron-Rich Foods – Need to fill body’s iron reserves before fall pregnant since low iron levels at the start of pregnancy puts mother at risk for postpartum anaemia.
  • Limit alcohol, caffeine – excessive alcohol consumption can lead to menstrual irregularities and impair ovulation in women and sperm production as well as quality in men.
  • Exercise – it is an integral part of any healthy lifestyle and will help with weight issues. Aim to exercise three to four days a week for 30 minutes. However, too much exercise has been shown to decrease testosterone, which can indirectly lower sperm counts in men and problems with ovulation in women.


Conceiving is a delicate process, and eating the right foods is essential to optimise reproductive potential. Indeed, a balanced diet will provide most of the nutrients you need. But the truth is that most people do not have a balanced diet and are unwittingly often deficient in important nutrients. If you decide to supplement your diet, be sure to follow these important guidelines:

Choose a multivitamin/mineral supplement that provide adequate amounts of vitamin B12, B6, zinc, selenium, magnesium, iron (in women) and zinc, folate, selenium (in men). Both parties should fuel up on Folic acid (400µg per day) and Omega-3 fats (1000-2400mg EPA plus DHA per day). Consider having Vitamin D levels checked. Vitamin D is categorised as a fat-soluble vitamin but actually functions as a hormone in the body. A recent study found that women with higher vitamin D levels were significantly more likely to achieve pregnancy compared to women with lower levels of vitamin D. Once pregnant, poor vitamin D status has been associated with certain pregnancy complications such as gestational hypertension and diabetes. Should you have a deficiency then it could be addressed by taking a supplement.

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