Most pregnancy symptoms are caused by rising levels of hCG, progesterone, and oestrogen. Common symptoms include nausea (affecting up to 80% of pregnant women according to NICE), fatigue, breast tenderness, and frequent urination. While most are harmless, certain warning signs such as severe headaches, visual disturbances, heavy bleeding, or reduced fetal movement require urgent medical attention.
The first trimester (weeks 1 to 12) brings the most dramatic hormonal changes of pregnancy. Human chorionic gonadotropin (hCG) levels double roughly every 48 hours in early pregnancy, peaking between weeks 8 and 11, according to the American College of Obstetricians and Gynecologists (ACOG).
Nausea affects approximately 70 to 80% of pregnant women, according to NICE guideline NG201 (2024). It typically begins around week 6, peaks between weeks 8 and 12, and resolves by week 16 for most women. If you cannot keep fluids down for more than 24 hours, contact your midwife or GP as you may have hyperemesis gravidarum.
Fatigue is one of the earliest pregnancy symptoms. Rising progesterone levels slow your metabolism. The NHS recommends resting when you can and accepting help from others. Iron-deficiency anaemia can worsen fatigue.
Sore, swollen breasts are among the first signs of pregnancy. Increased oestrogen and progesterone cause your milk ducts to begin developing from as early as week 4.
Your blood volume increases by about 50% during pregnancy. Combined with the growing uterus pressing on your bladder, you may visit the toilet more often from week 6. If you experience burning or pain, see your GP.
Hormonal fluctuations can cause mood swings. Perinatal mental health conditions affect up to 20% of women, according to the RCOG.
The second trimester (weeks 13 to 27) is often the most comfortable period. Nausea typically eases and energy levels improve.
The NHS recommends good posture, flat shoes, and gentle exercises like pregnancy yoga or swimming.
Up to 80% of pregnant women experience heartburn. Eating smaller meals and avoiding spicy foods can help.
The third trimester (weeks 28 to 40+) brings symptoms related to the increasing size of your baby and preparation for labour.
These practice contractions are usually irregular, painless, and short-lived. If contractions are regular and painful before 37 weeks, contact your maternity unit.
Mild swelling is normal in late pregnancy. Sudden or severe swelling can be a sign of pre-eclampsia and requires urgent assessment.
The NHS recommends sleeping on your side from 28 weeks. Research from Tommy's found back sleeping in the third trimester is associated with higher stillbirth risk.
The NHS emphasises that midwives would always rather you call and be reassured.
| Symptom | T1 | T2 | T3 |
|---|---|---|---|
| Nausea | Very common | Usually resolves | Rare |
| Fatigue | Very common | Improves | Returns |
| Back pain | Occasional | Common | Very common |
| Heartburn | Occasional | Common | Very common |
| Braxton Hicks | Rare | Occasional | Common |
| Swelling | Rare | Occasional | Common |
Yes, symptoms vary significantly between women and even between different pregnancies.
Most women notice symptoms between weeks 4 and 6, shortly after a missed period.
Yes, it is completely normal for symptoms to fluctuate day to day.
Normal symptoms are caused by hormonal changes. Warning signs requiring urgent attention include heavy bleeding, severe headaches with visual changes, sudden swelling, and reduced fetal movements after 28 weeks.
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