Gadsby R, Ivanova D, Trevelyan E, Hutton JL, Johnson S. The onset of nausea and vomiting of pregnancy: a prospective cohort study. BMC Pregnancy and Childbirth.. 2021; 21:(10)

Pregnancy sickness: new findings

02 February 2021
Volume 29 · Issue 2


Alexandra Uytenbogaardt, editor of BJM, discusses recent findings on pregnancy illness.

There has been a debate around whether the sickness women feel during the early stages of pregnancy is purely psychological rather than biological. However, the University of Warwick recently published a study called ‘The onset of nausea and vomiting of pregnancy: a prospective cohort study’ which suggests that there are biological factors that cause pregnancy sickness.

Pregnant women often experience some form of nausea in the first trimester, with symptoms subsiding usually between 12–14 weeks of pregnancy (Gadsby et al, 2021). The breakthrough in this study is that researchers have suggested that nausea and vomiting occur within a specific time frame following ovulation. ‘The precise course of pregnancy sickness is unknown but this research shows that it occurs at a specific developmental stage in a specific timeslot,’ says Professor Roger Gadsby, head author of the study. ‘For researchers, it narrows our focus in terms of where we look for the cause. If we know that symptoms occur in a very narrow window 8-10 days after ovulation, researchers can concentrate their efforts on that particular stage of development to find the cause of the condition, both anatomically and biochemically.’

This finding can further assist pregnant women when it comes to treating nausea and vomiting. ‘In the past, women suffering from nausea and vomiting in pregnancy have had their symptoms trivialised and overlooked because it was thought there was a psychological basis for the symptoms,’ Gadsby says. ‘This research further reinforces that nothing could be further from the truth, that this is a biological problem related to the development of the early fetus.’

Data was collected from 256 pregnant women's daily logs on their symptoms which detailed the beginning of their pregnancy sickness, comparing when it first started to that of the date of their last menstrual cycle and date of ovulation. By taking the measurement of symptoms of nausea from the date of ovulation as opposed to the last date of their menstrual period, it has revealed that symptoms of pregnancy sickness occur much earlier than what was originally thought. This suggests that the cause of the pregnancy sickness is related to a particular stage of development of the fetus.

What's even more interesting is that the researchers also found that the phrase ‘morning sickness’ has a negative connotation when referring to pregnancy sickness, nausea and vomiting because of pregnancy. Hence, they have suggested the phrases ‘pregnancy sickness’ and ‘nausea and sickness in pregnancy’ be used instead as it is a less trivial way of describing the condition.