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(Date of issue: July 2017, Version: 3)

This is a UKTIS monograph for use by health care professionals. For case-specific advice please contact UKTIS on 0344 892 0909. To report an exposure please download and complete a pregnancy reporting form. Please encourage all women to complete an online reporting form.


Orlistat is an orally administered gastric and pancreatic lipase inhibitor which reduces the absorption of dietary fat. Orlistat is used in conjunction with dietary measures to enhance weight loss in adults who are overweight (BMI ≥28). Systemic absorption of orlistat is expected to be negligible. Severe diarrhoea is a recognised side effect of orlistat and may reduce the availability of oral contraceptives, therefore use of additional contraceptive measures is advised.

The limited data on the use of orlistat in pregnancy do not suggest an increased risk of fetal congenital malformation but are too limited to exclude such a risk. There are no data on spontaneous abortion, intrauterine death, preterm delivery, low birth weight, or neonatal complications on which to assess risk. As orlistat may impair the absorption of fat soluble vitamins (A, D, E and K), there are theoretical concerns that its use during pregnancy may restrict nutrient availability to the fetus. Routine use in pregnancy is therefore not recommended.

Maternal obesity is associated with an increased risk of congenital malformations and adverse maternal and fetal outcomes; weight loss preconception is therefore recommended. Pregnant women with a BMI >30 should be advised to take 5mg folic acid supplementation one month before conception up until the end of the first trimester. Dieting or use of products to lose weight during pregnancy is not recommended.

Experience of orlistat use in pregnancy is limited. Where exposure in the first trimester has occurred, a detailed fetal anomaly scan should be considered in addition to any other antenatal investigations relating to the maternal obesity, and the drug discontinued as soon as pregnancy is diagnosed. Women and health professionals should be aware that antenatal detection of fetal anomalies is compromised with increasing BMI and that a normal scan is not informative with respect to neurodevelopmental outcomes. Other risk factors which independently increase the risk of adverse pregnancy outcome may be present in individual cases. Clinicians are reminded of the importance of consideration of such factors when performing case-specific risk assessments.

This document is regularly reviewed and updated. Only use full UKTIS monographs downloaded directly from to be sure you are using the most up-to-date version. The summaries of these monographs are openly available on

This is a summary of the full UKTIS monograph for health care professionals and should not be used in isolation. The full UKTIS monograph and access to any hyperlinked related documents is available to health care professionals at

If you have a patient with exposure to a drug or chemical and require assistance in making a patient-specific risk assessment, please telephone UKTIS on 0344 892 0909 to discuss the case with a teratology specialist.

If you would like to report a pregnancy to UKTIS please click here to download our pregnancy reporting form. Please encourage all women to complete an online reporting form.

Disclaimer: Every effort has been made to ensure that this monograph was accurate and up-to-date at the time of writing, however it cannot cover every eventuality and the information providers cannot be held responsible for any adverse outcomes of the measures recommended. The final decision regarding which treatment is used for an individual patient remains the clinical responsibility of the prescriber. This material may be freely reproduced for education and not for profit purposes within the UK National Health Service, however no linking to this website or reproduction by or for commercial organisations is permitted without the express written permission of this service. This document is regularly reviewed and updated. Only use UKTIS monographs downloaded directly from or to ensure you are using the most up-to-date version.