Obesity and Female Reproduction


Robert Norman of the University of Adelaide in Australia presented a very stat-heavy, but highly informative talk on the negative effects of obesity on female reproduction, findings which should increase the urgency with which physicians attempt to bring obesity under control in their patients.

Not only should the negative health effects spur physicians to action, but the heavier population as well; 50 percent of pregnancies today occur in women that are either overweight or obese.

And now for the facts:

Over-nutrition reduces reproduction

In cases of over-nutrition, puberty occurs earlier; anovulation, infertility, and menstrual abnormalties more common; and there is an increase in androgens and estrogens, and insulin.

Obesity and reproduction: Bad synergies

Prior to pregnancy, obesity increases the length of time to pregnancy, menstrual disorders, and in cases of assisted-reproductive technology, more drugs needed.

Further obesity increases the risk of genital tract infection, wound infection, urinary tract infection, pyrexia, and pre-eclampsia.

In early pregnancy, there is an increased risk of miscarriage and fetal anomalies.

During pregnancy the risks of gestational diabetes, high blood pressure, PET, DVT, and the need for instrumental and operative delivery, all increase.

Postpartum, hemhorragic infection and DVT are more prevalent.

Once the child is born, the mother is at an increased risk for diabetes mellitus, high blood pressure, and more chronic conditions.

Obesity may lead to infertility

There is abundant evidence for infertility in overweight women on natural cycles regardless of menstrual regularity, while there is also evidence for reduced success of ovulation induction.

Increased BMI (pre-pregnancy) affects fertility

The chances of conceiving per cycle are reduced by 8 percent in overweight women, and 18% in the obese. Further, it takes three months longer to become pregnant in the overweight and nine months longer in the obese.

Body shape affects reproductive outcomes

When looking at central and peripheral obesity in sperm donor pregnancies, it was discovered that women with central adiposity took longer to become pregnant, indicating that weight distribution is important as well as BMI.

Obesity increases miscarriage rates

Obesity very substantially increases the risk of miscarriage regardless of whether people have PCOS.

IVF treatment reduced pregnancy rates

There is clear evidence that patients with a high BMI are much less likely to become pregnant, and a substantially decreased chance with a BMI over 25.

Obesity affects miscarriage during IVF

The odds ratio of miscarriage increases when a person’s BMI goes over 30. The risks are equivalent to that of a women over age 40 giving birth.

Obesity and PCOS

PCOS is much more common among those with a high BMI compared to those with a lower BMI. This higher prevalence of PCOS likely means that increasing obesity uncovers and induces PCOS.

Effect of uterus vs egg on pregnancy

In cases in which an egg was donated by an individual with a normal BMI, but recipients had variable BMIs, recipients with a BMI over 30 had longer ongoing pregnancies.

Influence of insulin on obesity effects

Diet and exercise programs which reduce weight by 5 percent lead to the restoration of both menstrual cycles and fertility, though caloric restriction is more important than dietary composition. Insulin sensitizers (eg metformin, PPAR agonists) are able to restore menstrual cycles and fertility even without weight loss.

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