Morning sickness is believed to be caused by rising pregnancy hormones such as hCG and estrogen, plus a heightened sense of smell.
Causes
Experts believe rising levels of hCG, estrogen and progesterone, plus a heightened sense of smell, play a role. The exact cause is unknown.
How common
Up to 70% to 80% of pregnant women get nausea.
Timing
Starts around week 6 and often fades by week 14.
Relief
- Small meals.
- Ginger.
- Vitamin B6.
- Dry crackers.
Severe
Hyperemesis gravidarum affects about 1% to 3%. See a doctor.
Hormones and numbers
Nausea and vomiting of pregnancy affects roughly 70 to 80 percent of pregnant women, according to ACOG. It is linked to rising hCG and estrogen levels and a heightened sense of smell. Growth differentiation factor 15 (GDF15), studied in a 2023 Nature paper, appears to be a key trigger, with women exposed to lower levels before pregnancy more sensitive.
- Symptoms usually start by week 6 and peak at weeks 8 to 10, and ease by weeks 14 to 16 for most.
- Small frequent meals, ginger, vitamin B6 (10 to 25 mg, 3 to 4 times daily) and doxylamine are first-line options in ACOG guidance.
- Dehydration and weight loss over 5 percent need medical care.
Hyperemesis gravidarum
This severe form affects about 0.3 to 3 percent of pregnancies, with persistent vomiting, weight loss and need for IV fluids. It can need hospital treatment. Call the provider if you cannot keep fluids down for 24 hours, have dark urine, dizziness, or fainting.
Hormones and numbers
Nausea and vomiting affect up to 70 to 80 percent of pregnant women, usually beginning around week 6 and easing by weeks 12 to 14. It is linked to rising hCG and estrogen, increased sensitivity to smell and slower digestion. Ginger, small frequent meals, vitamin B6 and doxylamine are first line options per ACOG.
Hyperemesis gravidarum
About 1 to 3 percent of pregnancies involve hyperemesis gravidarum, which means persistent vomiting, weight loss over 5 percent, dehydration and electrolyte problems. It may need IV fluids and anti nausea drugs. Call a provider if you cannot keep fluids down for 24 hours.
Evolutionary theories and research
One theory suggests nausea protects the fetus from toxins in early development, and studies show women with morning sickness have lower miscarriage rates, about 3 percent versus 10 percent in some cohorts. hCG peaks at weeks 9 to 12 and parallels the timing of nausea. Genetic factors matter, as daughters of mothers with severe sickness have higher risk. GDF15 hormone levels have been linked with hyperemesis in a 2023 Nature study.
Treatments and guidelines
ACOG recommends vitamin B6 (10 to 25 mg three to four times daily) with or without doxylamine as first line. Ginger 1 g a day may help. Diclegis and Bonjesta are FDA approved combinations. Wrist bands have modest evidence. Severe cases need IV fluids and ondansetron or metoclopramide.
Based on data from the American College of Obstetricians and Gynecologists and Nature
