Weight and fertility

What is a healthy body weight?

There is no perfect way of defining a healthy body weight, since body frame and distributions of fat and muscle are different for everyone. In spite of its shortcomings, the best tool available for assessing body weight and health is body mass index (BMI), which you can calculate here. Then you can use this table to see which classification you are in.

BMI = weight (kg) / height (m2)

Example: You are 160 cm tall and weigh 65 kg.

Weight in Kilogram

Height in Centimetre

Weight in Pounds

Height in Feet and inches

Your Body Mass Index is:

BMI Value



Less than 18.5


18.5 to 24.9

Normal weight

25 to 29.9





How does weight affect fertility?

A healthy body weight is an important part of preparing your body for pregnancy. Studies show that being either underweight or overweight can affect the likelihood of conception. While body weight does influence fertility, problems with ovulation are most often caused by other factors.

If you are overweight or obese:
Being overweight may not increase your risk of having problems with ovulation, but obesity (BMI greater than 30) increases the risk of having abnormal ovulation and menstrual cycles. Obesity makes it more likely that it will take longer for you to get pregnant. Entering pregnancy with a body mass index (BMI) of 25 or more can also significantly increase your risk of having complications in your pregnancy. A small reduction in body weight of 2-5% can improve your chances of conceiving and having a healthy pregnancy. Women with polycystic ovarian syndrome have a metabolic condition that can lead to both overweight and problems with ovulation.

If you are underweight:
A BMI of 18.5 or lower may cause you to have a more difficult time getting pregnant and increases the risk of preterm birth. Many women with a BMI below 18.5 have irregular or absent periods, and may not be ovulating regularly. Gaining just a few pounds may make a difference in your likelihood of conceiving. Talk to your health care provider for guidance on how to gain weight.