A weighty issue
How a woman’s weight impacts the risk of miscarriage

A miscarriage is a devastating experience for couples, perhaps even more so for those who have struggled with infertility and gone through the initial joy of a successful fertility treatment. Statistics have shown that in both natural and IVF conception, about one in six pregnancies will end in a miscarriage before the 20th week, with the rate being higher in older couples.

Understandably, couples are frightened of miscarriages and would rather not think or talk about it. However, it is important for couples to understand why miscarriages happen, as well as what they can do to reduce their risks.

Although the exact reason for a miscarriage is often unexplainable, it can occur due to a number of reasons. These include chromosomal abnormality, improper implantation of the egg and maternal health problems or trauma. The mother’s age also plays a significant role, as does her lifestyle, which includes exposure to stress, smoking, drug use, malnutrition, excessive caffeine, radiation and toxins.

Another well-studied factor than increases a woman’s risk for miscarriage, is her weight. As these studies indicate, if the mother is obese or underweight, this increases her risk of not only infertility, but miscarriage as well, regardless of the method of conception.

According to researchers at the Department of Obstetrics and Gynaecology, University of Adelaide, Australia, being overweight increase a woman’s risk of miscarriage by 29%, while being obese can increase the risk by 71% or more. However, for women undergoing assisted reproduction, researchers at the Assisted Fertilization Center, Brazil concluded that maternal obesity could increase the risk of miscarriage by up to 1330%.

Obesity also compounds miscarriage rates in women with PCOS. The Department of Obstetrics and Gynecology, Faculty of Medicine, Erciyes University, Turkey found that the miscarriage rate in obese women with PCOS is about nine times higher than average.

And while miscarriage is often the result of an unhealthy fetus, researchers from the Department of Obstetrics and Gynecology, Stanford Hospital and Clinics, CA, USA found that the risk of miscarriage of a healthy fetus is significantly higher in obese women (with BMIs of 25 or more).

While obesity has been identified as a risk factor for spontaneous miscarriage, the mechanism for it remains unclear. But a study by The Academic Unit of Reproductive and Developmental Medicine, The University of Sheffield and Sheffield Teaching Hospitals, Sheffield, UK points to the endocrinological changes in obesity as possibily causing complex adverse effects including circulating adipokines, sex steroids and insulin resistance.

Women who are underweight, with a BMI of under 20, also face an increased miscarriage risk. A study by researchers at the German Cancer Research Centre found that pregnant women who were underweight faced a 70 % higher risk of having a miscarriage.

Therefore, it can be concluded that among intrauterine environmental factors, nutrition appears to play the most critical role in influencing placental and fetal growth. Since maternal undernutrition or overnutrition during pregnancy can impair fetal growth, women must adopt healthier diets and incorporate exercise to lower their risk of miscarriage.

If you have any concerns regarding miscarriage, especially after IVF, please do not hesitate to consult with your fertility consultant for advice.