Obesity—recurrent miscarriage

8.1

Introduction

Recurrent miscarriage (RM) is defined as loss of three or more consecutive pregnancies prior to 20 weeks of gestation, though some authors describe RM as two or more consecutive pregnancy losses.

The incidence of RM has been reported to be around 0.5%–2.3% and is rising in relation to the prevalence of obesity. It has been estimated that 1%–2% of second-trimester pregnancies miscarry before 24 weeks of gestation.

Approximately in 50% of couples with RM, the underlying cause remains unexplained after all investigations. Though this is reassuring it can be distressing for the couple.

In the United Kingdom, obesity affects one-fifth of the female population. Maternal obesity has been reported as a risk factor for adulthood obesity in offspring. Obesity may also lead to a poor pregnancy outcome like as sudden and unexplained intrauterine death.

Increased body mass index (BMI) has also been suggested as the second most significant factor predicting early pregnancy loss after advanced female age.

8.2

Obesity and miscarriage

Obesity is associated with low levels of adiponectin but raised levels of leptin in both serum and follicular fluid.

Higher levels of leptin can impair ovarian steroidogenesis. Low levels of adiponectin lead to higher levels of serum insulin levels which is one of the factors that increases levels of circulating androgens.

Therefore, obesity itself creates quite a hostile biochemical environment for the early stages of the developing gamete and pregnancy.

8.3

Obesity and recurrent miscarriage

A recent systematic review and meta-analysis has reported a significant association between excess weight and RM, independent of age as a risk factor.

The exact mechanism by which obesity increases the risk of miscarriage and RM is still not very clear. It is unlikely that the increased risk of miscarriage among obese patients can solely be attributed to Polycystic ovarian syndrome (PCOS) because of the low prevalence of PCOS in the general population with mostly spontaneous miscarriage.

The possible theories for the association between obesity and RM include the effect of obesity on endometrial development and the effect on oocyte quality.