Nausea and vomiting in pregnancy is not just ‘morning sickness’: data from a prospective cohort study in the UK

Background Nausea and vomiting in pregnancy is usually called ‘morning sickness’. This is felt by sufferers to trivialise the condition. Symptoms have been described as occurring both before and after noon, but daily symptom patterns have not been clearly described and statistically modelled to enable the term ‘morning sickness’ to be accurately analysed.

Aim To describe the daily variation in nausea and vomiting symptoms during early pregnancy in a group of sufferers.

Design and setting A prospective cohort study of females recruited from 15 May 2014 to 17 February 2017 by Swiss Precision Diagnostics (SPD) Development Company Limited, which was researching hormone levels in early pregnancy and extended its study to include the description of pregnancy symptoms.

Method Daily symptom diaries of nausea and vomiting were kept by females who were trying to conceive. They also provided daily urine samples, which when analysed enabled the date of ovulation to be determined. Data from 256 females who conceived during the first month of the study are included in this article. Daily symptom patterns and changes in daily patterns by week of pregnancy were modelled. Functional data analysis was used to produce estimated symptom probability functions.

Results There was a peak probability of nausea in the morning, a lower but sustained probability of nausea throughout the day, and a slight peak in the evening. Vomiting had a defined peak incidence in the morning.

Conclusion Referring to nausea and vomiting in pregnancy as simply ‘morning sickness’ is inaccurate, simplistic, and therefore unhelpful.