Smell perception during early pregnancy : no evidence of an adaptive mechanism

Objective It has been suggested that nausea and vomiting in pregnancy is an evolutionary adaptivemechanism to avoid the ingestion of potentially harmful foods. It has also been suggested that themechanism that triggers nausea and vomiting in pregnancy may be olfaction and that olfactory senses areinvoked to provide this protection. This study aimed to test this theory in a systematic design.Design Cross sectional study.Setting The antenatal department of a maternity hospital in the north of England.Sample Threegroupsofparticipants:pregnantwomen(n¼55),non-pregnantwomen(n¼42)andmen(n¼48).Methods Sensitivity was tested towards the odours of six standard stimuli (half safe and half associated withpotentially harmful compounds).Main outcome measures Odour rating of likeness, strength and pleasantness.Results Pregnant women rated safe and odours with potentially harmful compounds differently but not moreso than men or non-pregnant women. There was no evidence that pregnancy changed the olfactory processesfrom the non-pregnant state and only slight differences between pregnant women and men were recorded.Conclusions There was no evidence that olfactory processes had undergone any adaptation during pregnancy.Theabilitytodifferentiate safe frompotentiallyharmfulcompoundswas commontoallthreegroupsstudied.INTRODUCTIONNausea and vomiting in pregnancy, together with itsmore serious form hyperemesis gravidarum, is a majorhealth problem responsible for the loss of an estimated8.5 million working days per annum in the UK.