Friday, 17 April 2020


Sarah Baker RM, Fertility Midwife, St Jude's Hospital, Wolverhampton.

Maintaining a healthy weight is not only important for general wellbeing; studies have shown that obesity is also linked with a decline in overall fertility, the success rates of potential fertility treatments and pregnancy outcomes.

Increasing insulin levels associated with raised BMI can cause hormonal imbalances which have a direct impact on fertility.
            - In women, this can cause an increase in the levels of androgens (male hormones) which can inhibit ovulation causing irregular menstrual cycles. Even a small reduction in weight of just 5-10% can help to restore normal ovulatory functions and improve pregnancy rates.
- In men, severe obesity has been linked to raised oestrogen levels and decreased testosterone levels, which can affect sperm production, reducing sperm count and motility. Metabolic syndrome, a condition caused by obesity, can also lead to symptoms of erectile dysfunction.

Body Mass Index (BMI) may be used as a measure to determine healthy weight parameters, and is calculated by dividing weight (in kilograms) by height squared (in centimeters).

A normal BMI is defined as between
18.5 and 24.9.
A BMI of below 18.5 is in the underweight range.
A BMI between 25 and 29.9 is classified as overweight
BMI of >30 is categorised as obese.

          The following factors associated with raised BMI may complicate Fertility Treatments:
- Poor response to ovarian stimulation medications
- Difficulty titrating the dose of medications, in particular for women with
Polycystic Ovaries Syndrome (PCOS) and a greater risk of Ovarian Hyper-stimulation Syndrome (OHSS)
- A reduction in the number of eggs collected and more difficult Egg Collection/ Embryo Transfer procedures
- Lower success rates

In addition, raised BMI in pregnancy is associated with an increased risk of miscarriage, hypertension, Gestational Diabetes, pre-eclampsia, still birth and a number of other obstetric complications.

Information on how changes to diet and exercise regimes may aid weight loss can be found on the Department of Health website: The Eatwell Guide and Start Active, Stay Active Initiative. 

St Jude’s Hospital does not discriminate against women or their partners based on BMI and never refuse Fertility Treatments on this basis. However the clinic is committed to doing all we can to promote good health amongst our patients and assisting in weight loss journeys wherever possible, with a view to improving treatment success rates, lowering complication rates and improving pregnancy outcomes.
Spandorfer, Jump, Goldschlag et al: Obesity and in vitro fertilization: negative influences on outcome J Reprod Med 49: 973-977 2004

Maheshwari, Stofberg and Bhattacharya: Effect of overweight and obesity on assisted reproductive technology – a systematic review Human Reproduction Update 13: 433-444 2007

Robinson, O’Connell, Joseph et al: Maternal Outcomes in Pregnancies Complicated by ObesityObstetrics and Gynecology 106: 1357-1364, 2005

Chu, Callaghan, Kim et al: Maternal Obesity and Risk of Gestational Diabetes Mellitus Diabetes Care 30: 2070-2076 2007

Dokras, Baredziak, Blaine et al: Obstetric Outcomes after In Vitro Fertilization in Obese and Morbidly Obese Women Obstetrics and Gynecology 108: 61-69 2006

Diamanti-Kandarakis E, Bergiele A. The influence of obesity on hyperandrogenism and infertility in the female. Obes Rev. 2001; 2: 231-8

Ramsay JE, Greer I, Sattar N. Obesity and reproduction. British Medical Journal. 2006; 333(7579): 1159-62.

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