Nausea and vomiting are common in pregnancy, particularly in the first trimester, with the severity varying greatly among pregnant women. A range of non-pharmacological and pharmacological interventions can be used to assist in managing nausea and vomiting in pregnancy. Women may find these interventions useful, although the evidence for their effectiveness remains inconclusive.
Nausea and vomiting in pregnancy ranges from mild discomfort to significant morbidity. Symptoms generally start around 4–9 weeks of pregnancy . Nausea and vomiting due to other conditions (eg gastrointestinal, metabolic, neurologic or genitourinary) should always be excluded, particularly in women who report nausea or vomiting for the first time after 10 weeks .
The most severe form of nausea and vomiting in pregnancy is Hyperemesis gravidarum, which is intractable vomiting in early pregnancy, leading to dehydration and ketonuria severe enough to justify hospital admission and intravenous fluid therapy.
The cause of nausea and vomiting in pregnancy is not known but is probably multifactorial. The rise in human chorionic gonadotrophin during pregnancy has been implicated; however, data about its association with nausea and vomiting are conflicting .
54.1.1 Nausea and vomiting in pregnancy
- Prevalence: Nausea is the most common gastrointestinal symptom of pregnancy, occurring in 80–85% of all pregnancies during the first trimester, with vomiting an associated complaint in approximately 52% of women . Retching (or dry heaving, without expulsion of the stomach’s contents) has been described as a distinct symptom that is increasingly measured separately to vomiting and nausea .
- Timing: Most women report nausea and vomiting within 8 weeks of their LMP (94%), with over one-third (34%) reporting symptoms within 4 weeks of their LMP . Most women (87–91%) report cessation of symptoms by 16–20 weeks of pregnancy. Although nausea and vomiting is commonly referred to as ‘morning sickness’, only 11–18% of women report having nausea and vomiting confined to the mornings .
- Hyperemesis gravidarum: This condition is much less common, affecting 0.3–1.5% of women . Symptoms typically start between 5 and 10 weeks pregnancy and resolve by 20 weeks. However, up to 10% of women will continue to vomit throughout the pregnancy. The hospital admission rate for the condition falls from 8 weeks onwards .
54.1.2 Impact of nausea and vomiting in pregnancy
Although distressing and debilitating for some women, nausea and vomiting do not appear to have a negative impact on pregnancy outcomes. A systematic review of observational studies found a reduced risk of miscarriage associated with nausea and vomiting (OR 0.36; 95%CI 0.32 to 0.42) and conflicting data regarding reduced risk for perinatal mortality . No studies have reported an association between nausea and vomiting in pregnancy and teratogenicity .
However, despite reassurance that nausea and vomiting do not have harmful effects on pregnancy outcomes, these symptoms can have a severe impact on a pregnant woman’s quality of life. Two observational studies have reported on the detrimental impact that nausea and vomiting may have on women’s day-to-day activities, relationships, use of healthcare resources and need for time off work.
54.2 Managing nausea and vomiting in pregnancy
The systematic review conducted to inform these Guidelines identified additional evidence that was consistent with the NICE guidelines. The highest quality study, a Cochrane review examined 27 trials of interventions including acustimulation, acupuncture, ginger, vitamin B6 and several antiemetic medicines. Systematic review of studies in this area is complicated by the heterogeneity of studies and limited information on outcomes .
The available evidence suggests the following:
- Ginger: While small RCTs have found reduced severity of nausea and vomiting with ginger products (syrup or capsules) , there is limited and inconsistent evidence of their effectiveness, although there is evidence that their use may be helpful to women . Dosages of up to 250 mg four times a day appear to be safe .
- Acupressure, acustimulation and acupuncture: While some evidence from systematic reviews of RCTs supports the use of P6 acupressure and it appears to be safe in pregnancy , the evidence on the effectiveness of P6 acupressure, auricular acupressure and acustimulation of the P6 point is inconsistent and limited and there appears to be no significant benefit of acupuncture (P6 or traditional) .
- Pyridoxine (vitamin B6): There is limited evidence to support the use of pyridoxine and concerns about possible toxicity at high doses.
- Antihistamines: A meta-analysis of 12 RCTs that compared antihistamines ± pyridoxine with placebo or no treatment found a significant reduction in nausea in the treated group (OR 0.17; 95%CI 0.13 to 0.21) . A systematic review of three RCTs (n=389) found that phenothiazines reduced nausea or vomiting when compared with placebo (RR 0.31; 95%CI 0.24 to 0.42) , although different phenothiazines were grouped and one of the trials recruited women after the first trimester. The bulk of the evidence demonstrates no association between birth defects and phenothiazine use during pregnancy (n=2,948; RR 1.03; 95%CI 0.88 to 1.22) .
- Other pharmacological treatments: Antiemetic medicines are more likely to have a place in treatment of severe symptoms and the intractable nausea and vomiting of Hyperemesis gravidarum than in the relief of mild or moderate nausea and vomiting .
It is currently not possible to identify with certainty interventions for nausea and vomiting in early pregnancy that are both safe and effective. As nausea and vomiting mostly resolves within 16 to 20 weeks with no harm to the pregnancy, prescribed treatment in the first trimester is usually not indicated unless the symptoms are severe and debilitating .
Women who experience nausea and vomiting in pregnancy can be advised that, while it may be distressing, it usually resolves spontaneously by 16 to 20 weeks pregnancy and is not generally associated with a poor pregnancy outcome.
Approved by NHMRC in December 2011; expires December 2016
54.2.1 Discontinuing iron
Iron supplementation may be an aggravating factor in nausea and vomiting. The systematic review conducted for these Guidelines identified a prospective cohort studyin which 63 of 97 (p=0.001) women with severe nausea qualitatively reported an improvement in symptoms after discontinuing iron-containing antenatal multivitamins. If multivitamins are discontinued, consideration should be given to ensuring folate and iodine intake remain sufficient.
Discontinuing iron-containing multivitamins for the period that women have symptoms of nausea and vomiting may improve symptoms.
Approved by NHMRC in December 2011; expires December 2016
54.2.2 Oral health
Nausea and vomiting have the potential to affect oral health and women should be given advice on how to minimise these effects (see Chapter 16).
54.3 Practice summary: managing nausea and vomiting
At the first contact with all women and at subsequent contacts for women who report nausea and vomiting.
- Aboriginal and Torres Strait Islander health worker
- multicultural health worker
- Inform women that nausea and vomiting is not associated with medium or long-term adverse effects: Explain that nausea and vomiting is common in pregnancy, is not necessarily confined to the morning and is likely to lessen by week 16.
- Provide lifestyle/diet advice : Acknowledge that nausea and vomiting affects quality of life, and suggest tips on managing nausea and vomiting, including drinking plenty of fluids, eating little and often during the day, getting plenty of rest and avoiding fatty or spicy food. Avoiding iron-containing multivitamins while nausea and vomiting are present may also help.
- Discuss non-pharmacological and pharmacological treatments: If the woman asks about treatments for nausea and vomiting, suggest interventions that may help and are thought to be safe, beginning with non-pharmacological approaches. The safety and effectiveness of antiemetics should be discussed with women with more severe symptoms who choose to consider medication.
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