When Does Morning Sickness Start and End?
Medically reviewed by Rachel Liberto, RN on August 6, 2019
- Morning sickness most often starts between six and eight weeks of pregnancy (or two to four weeks after a missed period)
- 13 percent of women experience morning sickness before they’ve even missed their period
- 90 percent of women who experience morning sickness will first feel it by the eighth week
- Twenty to 30 percent of women with healthy pregnancies don’t experience any morning sickness
Once you’ve got your positive pregnancy test you may be waiting impatiently for morning sickness to start. An estimated 70 – 80 percent of pregnant women are hit with nausea during the first trimester, and 50 percent experiencing vomiting, both of which can happen at any time of day, not just the morning.
Can morning sickness start at one week?
The most common time for morning sickness to start is in the sixth week of pregnancy (two weeks after you miss your period). However, this is not a rule and the experiences of individual women vary considerably.
For around 13 percent of women, nausea can start before they even miss their period, which can be one of the earliest signs of pregnancy they experience. For 90 percent of women who experience morning sickness, it starts by the eight week of pregnancy.
How long does morning sickness last?
The most common pattern is for morning sickness to peak during weeks seven to nine, then tail off gradually after week 10. While pregnancy-related nausea (and, in some cases, vomiting) tends to start suddenly, for most women it tapers off more gradually than it started.
For an unlucky 10 percent of pregnant women, morning sickness actually gets worse after week nine.
Although feeling nauseous is no fun, the good news is that it signals a healthy pregnancy. Women with nausea have one third the chance of miscarrying compared to those with no nausea, as well as a lower chance of preterm labor.
What does morning sickness feel like?
Morning sickness feels a bit like being hungover. Most women describe it as a constant, unpleasant nausea.
Is it bad if I don’t have morning sickness?
While women who experience morning sickness have a lower chance of miscarrying, its absence certainly does not mean your pregnancy is doomed! About 20 – 30 percent of women have no nausea at all and go on to deliver perfectly healthy babies.
Your likelihood of experiencing morning sickness is also determined in part by:
- Your previous pregnancies. Morning sickness tends to be more severe with each subsequent pregnancy
- Your ethnic background. White women are more prone to nausea than Black or Asian women, and Black women are more likely to experience nausea that starts after the first trimester.
If you’re early in your pregnancy and worried because you don’t feel nauseous yet, chances are nausea will hit you in the next few weeks. It’s only in the eighth week of pregnancy that a lack of these symptoms predicts a higher chance of miscarriage, according to a prospective study that tracked 2,407 pregnant women from early in their pregnancies.
According to the study, as long as symptoms started by the eighth week, it didn’t make a difference in the miscarriage rate whether they started early or late. And once the first trimester was over, nausea (or lack thereof) had no bearing on the chances of pregnancy loss.
What causes morning sickness anyway?
No one really knows. Scientists debate whether it serves some kind of evolutionary purpose—perhaps reducing women’s likelihood of consuming spoiled food during pregnancy—or whether it’s simply an unpleasant side effect of increasing hormone levels.
It seems that levels of the hormone hCG play some role in morning sickness; hCG increases exponentially during the first few weeks of pregnancy and peaks between weeks 8 – 10, which coincides with the time when morning sickness is typically at its most severe. And conditions which cause higher than average levels of hCG, like Down’s Syndrome, molar pregnancies, and twins often cause more severe morning sickness.
However, there is a lot of variation in hCG levels in healthy pregnancies, and hCG levels do not reliably predict who gets morning sickness, who doesn’t, and how severe it is.
While no one understands exactly how, biologically, hCG might contribute to feeling nauseous, one thing that seems clear is that lack of symptoms does not cause a miscarriage. How do we know? Well, for one thing, treating morning sickness does not lead to worse pregnancy outcomes. Actually, the opposite is true: women who treat their morning sickness tend to have better outcomes than those who do not—not because treatment improves outcomes, but because if morning sickness is severe enough to require treatment, it usually signals a healthy pregnancy.