morning sickness in pregnancy
Reading File
Finding Sources
Finding Sources
Reading File
Reading File
Reading File
Reading File
I now have comprehensive information to provide a thorough answer. Let me synthesize it.
Morning Sickness (Nausea and Vomiting of Pregnancy)
Overview
"Morning sickness" is a misnomer — nausea and vomiting of pregnancy (NVP) typically occurs throughout the day, not just in the morning. A prospective study found that nausea occurring only in the morning affects just 2% of patients, while 80% of symptomatic women experience nausea or vomiting throughout the day.
Epidemiology
- Affects 50–80% of pregnant women
- ~4 million women annually in the United States are affected
- Symptoms typically begin between 4 and 10 weeks' gestation and resolve by week 20
- Only 3% of patients have significant NVP in the third trimester
- More common in Western countries and Japan; rare in Africa, Asia, and among Native Americans in Alaska — suggesting cultural/environmental contributions
Risk factors for more severe NVP:
- First pregnancy
- Younger maternal age
- Fewer than 12 years of education
- Non-smoking status
- Obesity
- Female fetus (for hyperemesis gravidarum)
Pathogenesis
The exact etiology is unknown, but several factors are implicated:
| Factor | Role |
|---|---|
| Human chorionic gonadotropin (hCG) | Temporal peak of hCG coincides with peak symptoms; conditions with elevated hCG (e.g., molar pregnancy, multiple gestation) are associated with more severe NVP |
| Genetic factors | Concordance in monozygotic twins; family history increases risk |
| Gastric dysrhythmias | Electrogastrographic recordings show altered gastric motility during NVP |
| Hormonal changes | Progesterone reduces GI motility; estrogen may contribute |
| H. pylori | Associated with hyperemesis gravidarum in some studies (heterogeneous evidence) |
| Prostaglandin E2 | Levels elevated during symptomatic episodes |
| Evolutionary theory | Some propose NVP is an adaptive response protecting the mother and fetus from harmful foods |
Severity Assessment — PUQE Score
The modified Pregnancy-Unique Quantification of Emesis and Nausea (PUQE) score assesses severity over the last 12 hours:
- Duration of nausea (1–5 points)
- Number of vomiting episodes (1–5 points)
- Number of dry-heave episodes (1–5 points)
Interpretation:
- Mild NVP: ≤6
- Moderate NVP: 7–12
- Severe NVP: >13
Diagnosis
Primarily clinical. Pain is usually absent (unless recurrent retching causes muscle strain). Laboratory studies are generally not indicated but may rule out mimics:
- Hepatitis
- Pancreatitis
- Pyelonephritis
- Uncontrolled diabetes (DKA)
Hyperemesis Gravidarum (HG)
The severe end of the NVP spectrum. Defined by:
- Persistent vomiting
- Dehydration
- Weight loss >5% of pre-pregnancy body weight
- Ketonuria
- Electrolyte disturbances (hypokalemia, metabolic alkalosis — NOT hyperkalemia or acidosis)
Peak incidence is around 10 weeks. Does not require abnormal vital signs for diagnosis and shares the same pathophysiologic pathway as NVP.
Management
Non-pharmacologic (first-line)
- Multivitamins started at conception may reduce incidence
- Ginger 500–1000 mg/day in divided doses (250 mg every 6 h) — accelerates gastric emptying, effective for mild symptoms
- Small, frequent meals; avoid foods with strong odors/seasoning
- Avoid iron supplements until second trimester (can worsen nausea)
- Favor protein-rich foods over fatty foods
- Acupressure at the P6 (Neiguan) wrist point — associated with symptom improvement
Pharmacologic Therapy
| Drug | Dose | Notes |
|---|---|---|
| Vitamin B6 (pyridoxine) | 10–25 mg TID | Best initial treatment; low side-effect profile |
| Doxylamine + B6 | 10 mg doxylamine + B6 | Combination very effective for mild-moderate NVP (was withdrawn in 1980s; hospital admissions doubled after withdrawal) |
| Antihistamines (dimenhydrinate, diphenhydramine) | Variable | Some efficacy; sedation common |
| Phenothiazines (promethazine, prochlorperazine) | Variable | Clinical efficacy shown; safety in pregnancy not fully established in controlled trials |
| Metoclopramide | 5–10 mg TID | Dopamine antagonist; useful adjunct |
| Ondansetron | 4–8 mg | Effective but some concerns about birth defects (cleft palate) in first trimester; use with caution |
| Corticosteroids | Short course | Reserved for refractory hyperemesis; avoid before 10 weeks |
For hyperemesis gravidarum: IV fluid resuscitation (normal saline or Lactated Ringer's), thiamine supplementation (to prevent Wernicke encephalopathy), correction of electrolytes, and parenteral antiemetics.
Prognosis
Compared to asymptomatic women, those with NVP are paradoxically associated with favorable birth outcomes overall, though they have a higher risk of preeclampsia. Symptoms resolve by 20 weeks in the vast majority of cases.
— Creasy & Resnik's Maternal-Fetal Medicine: Principles and Practice; Swanson's Family Medicine Review
This is a shared conversation. Sign in to Orris to start your own chat.