What are the first signs of pregnancy?

First Signs of Pregnancy

The earliest signs of pregnancy typically begin at 4-6 weeks gestational age and include nausea, vomiting, fatigue, and breast tenderness, with nausea and vomiting affecting 30-90% of pregnant women and peaking at 8-12 weeks. 1

Timing and Detection

• Biochemical detection precedes clinical symptoms: Human chorionic gonadotropin (hCG) becomes detectable in maternal blood 6-8 days after fertilization, with serum levels >5 mIU/mL confirming pregnancy. 1, 2
• Urine pregnancy tests with sensitivity of 25 units per liter can detect pregnancy 3-4 days after implantation, with 98% positive by 7 days (the time of the expected period). 2
• Ultrasound findings lag behind biochemical markers: the gestational sac (earliest sonographic finding) is typically visualized at 5 weeks gestational age, the yolk sac at 5½ weeks, and an embryo with cardiac activity at 6 weeks. 1

Common Early Symptoms by Trimester

First Trimester (Most Symptomatic Period)

Gastrointestinal symptoms dominate early pregnancy:

• Nausea and vomiting affect 30-90% of women, typically beginning at 4-6 weeks, peaking at 8-12 weeks, and subsiding by week 20. 1, 3, 4
• Nausea severity is highest during the first trimester, likely related to elevated human chorionic gonadotropin and estrogen levels, as well as changes in gastrointestinal motility from progesterone. 1
• Fatigue is reported by 77.9% of women in the first trimester and correlates positively with nausea severity—as nausea increases, fatigue worsens. 5, 6
• Breast pain and tenderness occur in 76.2% of women during the first trimester. 5

Cardiovascular and Physiologic Changes

Hemodynamic changes begin early and can manifest as symptoms:

• Heart rate increases starting at 20 weeks, rising by 10-20 beats per minute, particularly in the third trimester. 1
• Blood pressure decreases by 10-15 mmHg by 20 weeks due to peripheral vasodilation, then returns to pre-pregnancy levels by term. 1
• Cardiac output increases by 30-50% above baseline, primarily from increased stroke volume early in pregnancy. 1

Important Clinical Caveats

Common pitfalls in early pregnancy assessment:

• "Morning sickness" terminology is misleading: symptoms can occur throughout the day and may be minimized by both patients and providers, leading to undertreatment. 3, 4
• Early treatment prevents progression: addressing nausea and vomiting early may reduce progression to hyperemesis gravidarum, which can lead to dehydration and weight loss >5%. 1
• Abnormal findings require investigation: elevation in aminotransferases, bilirubin, or bile acids is abnormal in pregnancy and requires evaluation, as bilirubin and bile acids should remain normal throughout pregnancy. 1
• Symptoms overlap with pathology: abdominal symptoms during pregnancy can represent normal pregnancy changes or serious conditions unique to pregnancy (hyperemesis gravidarum, intrahepatic cholestasis, acute fatty liver, preeclampsia). 1

Symptom Management Approach

Stepwise treatment for nausea and vomiting:

• Initial management: dietary modifications (small, frequent, bland meals; BRAT diet—bananas, rice, applesauce, toast), avoiding triggers, and lifestyle changes. 1
• First-line pharmacologic therapy: vitamin B6 (pyridoxine 10-25 mg every 8 hours) combined with doxylamine (10-20 mg), which is FDA-approved and recommended by ACOG. 1
• Second-line options: H1-receptor antagonists (promethazine, dimenhydrinate), ondansetron, metoclopramide, or intravenous glucocorticoids for moderate to severe cases. 1

Women often avoid medications due to fetal safety concerns, leading to undertreatment despite availability of safe, effective options. 3, 4, 5