Researchers pinpoint three days when pregnancy is most likely to start

A team of researchers from the University of Warwick has pinpointed the three days when pregnancy sickness, characterised by nausea and vomiting, is most likely to start.

The novel study opens up the possibility for scientists to identify a biological cause for the condition.

By measuring the onset of symptoms from a woman's date of ovulation for the first time, rather than last menstrual period, they have demonstrated that symptoms start earlier in pregnancy than previously thought, and within a smaller time frame.

Nausea and vomiting in pregnancy, often referred to as pregnancy sickness, which usually ends by 12 -14 weeks of pregnancy is experienced by most women during pregnancy although some will experience it more severely, as in the case of hyperemesis gravidarm when the symptoms can continue throughout the pregnancy.

The cause has historically often been seen as psychological but this latest study reinforces the view that the cause is biological and is linked to a specific developmental stage of pregnancy.

Researchers from Warwick Medical School and the Department of Statistics at the University of Warwick have drawn their conclusions from a unique dataset collected at the Clearblue Innovation Centre, by SPD Development Company Ltd.

Their results, published in the journal BMC Pregnancy and Childbirth, identify a specific time period during pregnancy that could point scientists to an anatomical or biochemical cause for the condition.

The date of a woman's last menstrual period is commonly used to measure the start of pregnancy, but their date of ovulation is thought to be a more accurate starting point as menstrual cycles can vary greatly between individuals, and even between cycles for the same individual.

The researchers used data from daily symptom diaries kept by 256 pregnant women to compare the start of their nausea and vomiting symptoms to the date of their last menstrual period and date of ovulation, as determined by a urine test.

Using their date of ovulation as the start of pregnancy most women experienced the first symptoms of pregnancy sickness after 8 to 10 days, compared to 20 to 30 days if measured from their last menstrual period.

This story has been published from a wire agency feed without modifications to the text.