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New Study Pinpoints Three Day Window for Pregnancy Nausea to Begin

woman holding pregnancy test at home

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Key Takeaways

  • Nausea and vomiting, known as "morning sickness," is one of the most common symptoms of pregnancy.
  • A new study pinpoints a three-day window for the start of pregnancy sickness, which may help establish a biological cause.
  • The study also found that 94% of pregnant people experience some form of pregnancy sickness—a much higher number than previously reported.

One of the less-than-pleasant side effects of pregnancy—for the majority of expectant moms—is nausea, commonly known as "morning sickness."

Despite the prevalence of this particular pregnancy symptom, scientists never have been able to pinpoint a single cause. But new research from the Warwick Medical School and the Department of Statistics at the University of Warwick in the UK narrows the time frame for the start of pregnancy sickness to just three days, providing the opportunity to identify a biological cause.

Incidentally, the term "morning sickness" to describe nausea and vomiting during pregnancy is a misnomer. An earlier study from the same team from Warwick confirmed what generations of pregnant people can attest to—the sickness can occur at any time of the day. 

Sherry Ross, MD

Reassuring women who don’t see a light at the end of the tunnel is important so they understand pregnancy sickness is common, it’s short lasting, and it suggests your pregnancy is off to a healthy start.

— Sherry Ross, MD

Study Findings 

The study, published in the BMC Pregnancy and Childbirth, involved 256 pregnant women, who recorded their daily pregnancy symptoms in diaries, as well as the date of their last menstrual period and the date of ovulation (confirmed by a urine test). When the Warwick researchers, led by Professor Roger Gadsby, MBE, compared the entries, they found that most women started getting "the sickness" 8-10 days after ovulation.

Professor Gadsby, an honorary associate clinical professor at Warwick Medical School, says the traditional method of dating a pregnancy from the first day of the last menstrual period (LMP) is unreliable. "Women may not remember the date of their LMP, and the period cycle is not usually regular and often varies between 26-35 days," he explains. 

In this study, the date of ovulation was measured by testing a daily urine sample to give a precise date to use to date the pregnancy.

Professor Roger Gadsby, MBE

We now know a more precise time when [pregnancy sickness] symptoms start. This enables researchers looking for the cause of the condition to concentrate their efforts on a short time frame and to examine what is happening in the mother, in the developing embryo, and at their interface during this short time period.

— Professor Roger Gadsby, MBE

The findings are important, because previous research using LMP to date pregnancy suggested that there was a period of between 4-6 weeks during which pregnancy sickness symptoms started. "We were surprised that there was such a narrow window of around three days (days 8-10 from ovulation) when pregnancy sickness symptoms started," Professor Gadsby says.

This narrow time window is further evidence of the biological cause for pregnancy nausea and vomiting. In the past, some researchers have suggested a more psychological/psychiatric cause, which sufferers have felt has stigmatized and played down the importance of the condition.

The research also discovered that 94% of women do experience some form of pregnancy sickness, a rate much higher than previously thought. This is because mild early symptoms that tend to fade by around 7-8 weeks into pregnancy were picked up. In other studies, those symptoms would have faded before the research even began.

Will We Ever Know What Causes Pregnancy Sickness?

Yes, Professor Gadsby says. "We now know a more precise time when the symptoms start," he explains. "This enables researchers looking for the cause of the condition to concentrate their efforts on a short time frame and to examine what is happening in the mother, in the developing embryo, and at their interface during this short time period."

"Most healthy pregnancies have some degree of morning sickness," says Sherry Ross, MD, an obstetrician-gynecologist and women’s health expert at Providence Saint John’s Health Center in Santa Monica, California. In her experience, some women experience nausea as early as 2 weeks of being pregnant, and nausea peaks around 8 weeks into the pregnancy. "Sickness can continue until 12 weeks," she adds.

How To Handle Pregnancy Sickness

To avoid nausea during pregnancy, Dr. Ross suggests eating frequently and often. "Don’t wait to feel hungry to eat," she says. "Ideally, choose foods high in carbohydrates and low in fat, but avoid foods that are spicy, salty, or high in protein." She recommends the BRAT (Bananas, Rice, Applesauce, and Toast), along with cold, clear, and carbonated beverages in small amounts and as often as possible.

If you need medication to relieve nausea or vomiting, the safest option for pregnancy is Diclegis, Dr. Ross adds. She also suggests trying some natural remedies, such as vitamin B6. "It's not clear how it works but it has a great track record," she says. The recommended dose is 25mg, three times a day.

Another natural remedy is ginger in various forms, such as ginger root boiled in water, ginger root tea, ginger lozenges, ginger nonalcoholic beer, or ginger gum or capsules. "It's thought that ginger helps relax gastrointestinal muscles, thereby relieving symptoms associated with morning sickness," Dr. Ross explains.

Other easy, safe ways to try to relieve morning sickness are acupuncture and acupressure, which use the PC6 pressure points to treat mild nausea and vomiting.

What This Means For You

If you're experiencing pregnancy sickness (be it nausea, vomiting, or both) and it prevents you from drinking or eating for more than 24 hours, it's time to speak to your doctor. You know your body best, and if you're feeling unusually tired or unable to tolerate foods or fluids for prolonged periods, it's best to get some advice.

"Reassuring women who don’t see a light at the end of the tunnel is important so they understand pregnancy sickness is common, it’s short lasting and it suggests your pregnancy is off to a healthy start," Dr. Ross says.

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  1. Gadsby R et al. Nausea and vomiting in pregnancy is not just 'morning sickness': data from a prospective cohort study in the UK. British Journal of General Practice. 2019 Dec. doi:10.3399/bjgp20X710885