Bleeding during pregnancy can be worrying — from light spotting to heavier fresh bleeding. Important: a true menstrual period does not occur during pregnancy. This guide explains the differences, typical causes, warning signs and next steps. Authoritative background information is available from the NHS, the ACOG FAQ, NICE guidance NG126 (ectopic pregnancy & miscarriage) and patient information from the RCOG.
Why a period is not possible during pregnancy
Menstruation is the shedding of the uterine lining without pregnancy. If pregnancy has occurred, the lining is maintained to support the embryo. Bleeding in pregnancy therefore has other causes — it is never a regular period.
Period vs pregnancy bleeding — clear differences
Period: heavier, steady blood flow over 3–7 days, occurs cyclically, often with cramp-like period pain.
Pregnancy bleeding: usually spotty or staining, light to dark red, lasts from hours to a few days, not cyclical.
Quick check: colour, amount & accompanying signs
- Light pink or brown, very little: often implantation bleeding or hormonal withdrawal bleeding around the expected period date.
- Bright red after sex/examination: typical contact bleeding from the sensitive cervix, usually settles quickly.
- Dark red, heavier, with tissue fragments: warning sign of a possible miscarriage — seek medical assessment.
- Sudden heavy bleeding + one-sided pain/dizziness: possible ectopic pregnancy or placental complication — attend the emergency department immediately.
Common causes of bleeding in pregnancy
Implantation bleeding
6–12 days after fertilisation: small vessels can break when the blastocyst implants. Very light, pink or brown, maximum 1–2 days. More information from ACOG.
Pseudo-menstruation (hormonal withdrawal bleeding)
Short-term hormonal fluctuations can cause light bleeding around the expected period date. Much lighter and shorter than a normal period.
Contact bleeding
During pregnancy the cervix is highly vascular. A vaginal examination or sex can irritate small vessels. Bright red, usually stops within a few hours.
Cervical causes, infections & minor injuries
Cervical polyps, ectropion, bacterial vaginosis or yeast infection can cause spotting. Swabs and targeted treatment may be needed. Information: NHS.
Subchorionic haematoma
Collection of blood between the chorion and the uterine wall. Common finding on early pregnancy ultrasound. Management depends on size and follow-up.
Ectopic pregnancy (extrauterine)
From around 5–6 weeks' gestation: one-sided severe pain, dizziness, sometimes heavy bleeding. Life-threatening if it ruptures. Immediate assessment required. Guidance: NICE NG126.
Miscarriage
Increasing bleeding, cramp-like pain, possible passage of tissue. Diagnosis by ultrasound and serial hCG measurements. Patient information: RCOG.
Placental complications (2nd/3rd trimester)
Placenta praevia: painless, fresh bright red bleeding. Placental abruption: usually painful with a hard uterus. Late bleeding always requires hospital assessment. Overview: NHS.
Frequency by trimester
| Trimester | Typical causes | Assessment |
|---|---|---|
| 1st trimester (0–12 weeks' gestation) | Implantation, hormonal withdrawal bleeding, contact bleeding, subchorionic haematoma, ectopic pregnancy, miscarriage | Light bleeding is common; always discuss with a healthcare professional. |
| 2nd trimester (13–27 weeks' gestation) | Less common; assessment mainly for placental location (praevia), cervical length, infections | Fresh bleeding should be assessed (GP or hospital). |
| 3rd trimester (28–40 weeks' gestation) | Placenta praevia, placental abruption, vasa praevia, blood-stained show as a sign of labour | Fresh bleeding can be serious — attend hospital immediately, especially with pain or dizziness. |
Diagnosis: what rules out what?
- Transvaginal ultrasound: position of gestational sac/embryo, heart activity, placental location, haematomas.
- Serial hCG & progesterone: course over time to distinguish a viable from a non-viable pregnancy.
- Vaginal swabs: detection of BV/yeast, with treatment if needed.
- Blood group & rhesus status: for Rhesus D-negative women, anti-D prophylaxis may be considered depending on the situation (after bleeding/trauma/procedures — follow local guidance).
Diagnostic pathways: NICE NG126. Concise patient information: RCOG and the NHS.
Self-help & behaviour until assessment
- Observe: note colour, amount, duration & accompanying symptoms (pain, fever, dizziness).
- Pads rather than tampons or cups: more hygienic and allows better assessment of blood loss.
- Rest: avoid vaginal intercourse for now, no heavy lifting; reduce stress.
- Medications: painkillers only after medical advice; fever and severe pain are warning signs.
Immediate hospital care — these signs are an emergency
- heavy fresh bleeding or circulatory symptoms (dizziness, fainting, clammy skin)
- one-sided severe abdominal/shoulder pain (suspected ectopic pregnancy)
- bright red bleeding in the 2nd/3rd trimester, even without pain (placenta praevia)
- painful bleeding with a hard abdomen (placental abruption)
- fever or foul-smelling discharge
Conclusion
In pregnancy: there is no true period — but bleeding can occur. Light spotting may be harmless, while fresh bright red or heavy bleeding is a warning sign. Monitor colour and amount, rest, use pads and have bleeding assessed by a clinician promptly. If you have pain, dizziness or late bleeding: go to hospital immediately.