Can someone really be too skinny to conceive? Yes! While we have always known that being obese affects the chances of conception, being too skinny is now also linked with fertility problems.
By Christel Gomes
Skinny is ‘in’ for women in our culture. If you’ve never been guilty of it yourself, it is almost certain that you have at least one or two girlfriends who are on a diet or who are perpetually trying to lose weight, even though they don’t look like they need to.
Subjective per ceptions of beauty notwithstanding, when we come down to hard medical facts, being too skinny can be detrimental to fertility.
Dr Ida Ismail-Pratt, associate consultant at NUH Women’s Centre explains why: “Fertility depends on your body’s ability to release an egg during your menstrual cycle. Body fat is an important ingredient in the making of the hormones that help you have a regular menstrual cycle. Insufficient body fat may lead to very irregular menses or none at all (amenorrhea). This can decrease your monthly potential to ovulate and affect your fertility.”
What’s Too Skinny?
So what exactly is “too skinny”? Dr Seng Shay Way, specialist in Obstetrics and Gynaecology, and consultant at Raffles Fertility Centre says a woman’s
Body Mass Index (BMI) is a good gauge to use. BMI is a measure of body fat based on a calculation of height and weight.
“You need to have a minimum body fat content of 18 to 22 per cent to have normal periods and to ovulate. If a women’s BMI is 18.5 to 20, she is skinny and if she falls below 18 she is borderline anorexic,” says Dr Seng.
Generally, the classification of BMI is as follows:
BMI of less than 18.5 – Underweight
BMI 18.5-24.9 – Normal weight
BMI 25-29.9 – Overweight
BMI 30 and greater – Obese
Dr Ismail-Pratt adds that if you fall into the underweight category, you might be at risk of nutritional deficiencies, osteoporosis and having an irregular menstrual cycle which puts you at increased risk of infertility.
Even if your periods remain regular, it still doesn’t mean you’re ovulating. Dr Abel Soh, specialist in
Endocrinology and consultant at Raffles Diabetes & Endocrine Centre informs us that, “there can be absence of ovulation even if the woman continues to have regular periods.”
Let’s Get Scientific
So how exactly does the amount of body fat you have translate to an irregular period or a lack of ovulation? Dr Seng explains, “If your body fat is too low, it disrupts the flow of hormones from your brain to your pituitary gland. Both follicular stimulating hormones (FSH) and luteinizing hormones (LH) are suppressed which results in an ovulation, a drop in oestrogen and irregular menses. If ovulation does not occur, there is no way you can conceive.”
Excessive exercise also leads to problems. “If you exercise excessively, you may not ovulate each month, or have regular periods,” continues Dr Seng. “This happens to some professional athletes and ballet dancers. Some female athletes can have body fat as low as eight or 10.”
"Insufficient body fat may lead to very irregular menses or none at all (amenorrhea). This can decrease your monthly potential to ovulate and affect your fertility"
That said, if an underweight woman does get pregnant, it’s not to say that her problems are over. According to Dr Seng, “Underweight women are more likely than those of normal weight to have a preterm delivery or a low-birth-weight infant.”
The good news is that our expert also adds that risk of most other complications of pregnancy is no greater than that of normal-weight women.
Too Skinny vs. Too Heavy – Which is Worse?
According to Singapore Gynaecologist, Dr Kelly Loi, of the Health & Fertility Centre for Women at Paragon Medical, “being obese is well documented to also impair fertility and lead to irregular menstrual cycles. Both cases are not ideal, and there are insufficient studies to show which is truly worse”.
Obesity increases your risk of diabetes, hypertension, stroke and heart problems. Obesity also increases your risk of getting pre-eclampsia and diabetes in pregnancy, which will increase the chances of having a preterm delivery or low birth weight baby. “If you are obese and diabetic, you also have a higher risk of miscarrying in early pregnancy,” Dr Ismail-Pratt informs us.
Dr Seng agrees, adding that being obese or overweight doubles a woman’s risk of miscarriage following IVF. “Both implantation (pregnancy) and live birth rates are lower in overweight women, and this is most likely due to an increase in estrogens and in male hormones. When a woman has high levels of testosterone, she may be prone to infertility.”
On the other hand, according to Dr Loi, if you are going through your pregnancy while underweight, there is also higher risk of miscarriage and delivery of an underweight baby. “After delivery, evidence also
indicates the mother may experience increased exhaustion and depression when the baby is born,” she says. On top of that, being underweight may also increase the chance of complications during fertility treatment and pregnancy and increase the risk of premature delivery and neo-natal death.
The Sweet Spot for Fertility
There is, however, a sweet spot when it comes to fertility. “There is a weight range that is considered ideal. For fertility, ideally your BMI should be between 20 and 24,” says Dr Seng.
His advice is that if you are underweight, see your doctor or dietitian for an evaluation and together, plan how to meet your goal weight. Dr Loi agrees and adds that a preconception visit can also help identify other disorders and underlying conditions which may affect weight and impact pregnancy, including possible thyroid disease, and other hormonal disorders.
“For underweight women, it would be ideal to try to optimize the weight first with a healthy diet and lifestyle. Once pregnant, the use of various prenatal supplements may also help ensure sufficient essential vitamins and minerals for the baby. Sufficient weight gain should also be encouraged through good nutrition during the pregnancy,” she says.
If you are already pregnant and find you are losing weight through your pregnancy, Dr Soh cautions that you need to be evaluated for possible hyperthyroidism (overactive thyroid) so that any problems that can affect both you and the baby can be treated.
Tips For Weight Gain
There are of course healthy ways to gain weight if you are underweight and hoping to get pregnant soon. Dr Seng gives us the following tips:
1 Eat more frequently. When you’re underweight, you may feel full quicker. Eat five to six smaller meals during the day rather than two or three large meals.
2 Choose nutrient-rich foods. Whole-grain breads, pastas and cereals; fruits and vegetables; low-fat dairy products; lean protein sources; and nuts and seeds, are all a healthy way to put on some weight.
3 Try smoothies and shakes. Don’t fill up on diet soda, coffee and other drinks with few calories and little nutritional value. Instead, drink smoothies or healthy shakes made with low-fat milk and fresh or frozen juice, and sprinkle in some ground flaxseed. In some cases a liquid meal replacement beverage may be recommended. Drink fluids either 30 minutes before or after a meal to avoid becoming full before you eat.
4 Have calorie-dense snacks daily. Snack on nuts, peanut butter, cheese, dried fruits and avocados. Have a bedtime snack, such as a peanut butter and jelly sandwich or a wrap sandwich with avocado, sliced vegetables, and lean meat or cheese.
5 Top it up. Add extras to your dishes for more calories. Cheese in casseroles, soups, scrambled eggs, and non-fat dried milk in stews are all good additions to your meals.
Pregnancy is hard enough without having to worry about additional complications. If you’re planning for a family, sort out your own weight first, the healthy way.