pregnancy-birth

Bleeding in Pregnancy: What It Means, Trimester by Trimester

By Dr. Adeeb Alshahrour · June 15, 2023

A white sanitary pad on a pink background, scattered with small red paper flowers

Bleeding happens in roughly one in four pregnancies, and a large share of those pregnancies go on completely normally. That is genuinely reassuring — but it is not a reason to wait.

The reassurance only applies after an evaluation, because the harmless causes and the dangerous ones look identical at the start. Light pink spotting at seven weeks can be implantation-related, or it can be the first sign of a tubal pregnancy that will rupture in two days. You cannot tell from the outside, and neither can we over the phone.

So the rule for this entire article is simple: any bleeding in pregnancy gets reported, and most of it gets an ultrasound. Nothing below is permission to watch and wait.

Go to the emergency department now

Do not call and wait for a callback. Do not wait until morning. Go, and call us on the way if you can.

Heavy bleeding — soaking a pad in an hour or less, or passing large clots
Bleeding with severe pain on one side of the lower abdomen — the classic ectopic pattern
Pain at the tip of your shoulder, especially with dizziness. This is blood irritating the diaphragm from internal bleeding, and it is an emergency even if the vaginal bleeding is light
Any bleeding after 20 weeks, in any amount, with or without pain
Bleeding with fever or chills, or foul-smelling discharge
Feeling faint, lightheaded, clammy, or having a racing heart — the amount you can see is not always the amount you are losing
Constant, hard, painful abdomen with bleeding, particularly in the third trimester
Bleeding after a fall, a car accident, or a blow to the abdomen, even if it seems minor

If you are Rh-negative, mention it at the door. It changes what needs to happen in the next few hours.

First trimester bleeding

About a quarter of pregnancies bleed in the first 12 weeks. Here is the differential, roughly in order of how often it turns out to be each one.

Implantation bleeding

Around 6 to 12 days after conception — often right when a period was expected — the embryo embeds in the uterine lining and can cause light pink or brown spotting for a day or two. It is lighter and shorter than a period and does not build. Genuinely harmless. But it is a diagnosis you can only make in hindsight, once everything else has been excluded, and it does not explain bleeding at nine or ten weeks.

Subchorionic haematoma

A collection of blood between the gestational sac membranes and the uterine wall, seen on ultrasound. It can cause anything from spotting to a frightening gush of bright red blood. Most resolve on their own and most pregnancies with one continue normally, especially when the haematoma is small and the fetal heartbeat is present. Larger collections carry a modestly higher risk of miscarriage, preterm birth, and abruption, so we usually repeat the ultrasound to confirm it is shrinking.

Miscarriage

Bleeding is the most common presenting sign, usually with cramping that feels like strong period pain, low and central rather than one-sided. Roughly 1 in 5 recognised pregnancies end in miscarriage, the great majority from chromosomal errors in the embryo — not from exercise, stress, sex, lifting a toddler, an argument, or anything you ate. Nothing you did caused it and nothing you could have done would have prevented it.

Diagnosis rests on ultrasound plus, sometimes, serial hCG blood levels 48 hours apart. Depending on the findings and your preference, management is expectant, with medication (mifepristone followed by misoprostol is more effective than misoprostol alone), or with a short suction procedure. All three are reasonable; the choice is largely yours.

Ectopic pregnancy

The pregnancy implants outside the uterine cavity, most often in a fallopian tube. It occurs in about 1 to 2 of every 100 pregnancies and it is the reason first-trimester bleeding is never dismissed.

Classic features are bleeding, one-sided pelvic pain, and a positive pregnancy test with an empty uterus on ultrasound. But it does not always follow the script — some women have almost no pain until rupture. Shoulder-tip pain, fainting, or sudden severe pain means a ruptured tube and internal bleeding, which is life-threatening.

Higher risk with prior ectopic, prior tubal surgery or tubal ligation, pelvic inflammatory disease or chlamydia, endometriosis, IVF, or conception with an IUD in place. Treatment is methotrexate if caught early and stable, surgery if not. An ectopic pregnancy cannot be moved to the uterus and cannot continue.

Molar pregnancy

Uncommon, but worth naming. Abnormal placental tissue grows instead of a normal pregnancy, causing bleeding that is often dark brown, a uterus larger than expected for dates, severe nausea and vomiting, and a very high hCG. Ultrasound is usually diagnostic. It is treated with suction evacuation followed by hCG monitoring until it returns to zero, because a small proportion need further treatment.

Cervical and vaginal causes

The cervix in pregnancy is engorged and fragile. Light spotting after sex, after a pelvic exam, or after a transvaginal ultrasound is common and typically stops within a day. A cervical polyp or an infection can do the same. This is still worth a call, and it is still worth a look — this is the category where a cervical cancer screening that is overdue occasionally changes the picture. Bleeding after sex should never be assumed to be "just the cervix" without an exam.

Second and third trimester bleeding

After 20 weeks, the calculation changes. Bleeding is less common and more likely to matter, so the default is immediate evaluation at labour and delivery, not the office.

Placenta praevia

The placenta lies over or close to the cervix. The hallmark is painless, bright red bleeding, often starting in the late second or third trimester and often stopping on its own before returning heavier.

A low-lying placenta on the 18–22 week anatomy scan is common and most resolve as the uterus grows; a repeat scan in the third trimester settles it. If praevia persists, delivery is by planned caesarean and vaginal exams are avoided. Related conditions — vasa praevia and placenta accreta spectrum — are also identified on ultrasound and change the delivery plan substantially, which is one concrete reason the anatomy scan matters. See labor and delivery for how a planned caesarean is arranged.

Placental abruption

The placenta separates from the uterine wall before birth. Typically painful bleeding, with a uterus that feels hard and tender and contractions that do not fully relax between. Crucially, blood can be trapped behind the placenta, so the visible bleeding badly understates the loss. Risk is higher with high blood pressure or preeclampsia, smoking or cocaine use, trauma, a previous abruption, and after the waters break in a pregnancy with excess fluid.

Abruption is an emergency for both mother and baby. This is the single strongest reason no bleeding after 20 weeks is ever managed by phone.

Preterm labour

Bleeding or blood-streaked mucus before 37 weeks, with regular contractions, pelvic pressure, low backache, or a change in discharge, needs assessment. Steroids given in time meaningfully improve newborn outcomes, and that window closes.

Bloody show

At term, as the cervix softens and opens, the mucus plug comes away — thick mucus streaked pink or brown. This is normal, expected, and often precedes labour by hours to days. It is mucus with streaks. Bright red blood that flows, soaks, or clots is not a show, and being at 39 weeks does not make it harmless.

Uterine rupture

Rare, and mainly a consideration for anyone labouring after a previous caesarean. Sudden severe abdominal pain, bleeding, and an abnormal fetal heart rate. Managed in hospital, which is one reason a trial of labour after caesarean happens where an operating theatre is immediately available.

What happens when you come in

Vital signs and how much you are bleeding — pulse and blood pressure often reveal more than the pad does
Ultrasound — location of the pregnancy, fetal heartbeat, placental position, and any haematoma. Transvaginal in early pregnancy, and it is safe
Blood tests — hCG (sometimes repeated in 48 hours), full blood count, and blood type with Rh status
Speculum examination to see whether blood is coming through the cervix, and whether the cervix is open. Not done, or done with great caution, if praevia is suspected
Fetal monitoring after about 24 weeks

Rh status and anti-D — do not skip this

If your blood type is Rh-negative and the baby is Rh-positive, fetal blood cells entering your circulation can prompt your immune system to make antibodies against them. It rarely harms the current pregnancy. It can seriously harm the next one.

Any bleeding episode in pregnancy is a reason to check your Rh status and, if you are Rh-negative, to receive Rh immune globulin (anti-D, often called RhoGAM). It is one injection, ideally within 72 hours of the bleed. Doses are also given routinely at 28 weeks, after delivery of an Rh-positive baby, and after miscarriage, ectopic pregnancy, amniocentesis, external cephalic version, or abdominal trauma. This single injection is why haemolytic disease of the newborn is now rare, and it only works if it is given in time.

Your blood type is drawn at your first prenatal visit as part of prenatal care. If you do not know it, find out.

What to do while you are on your way

Note the timing, the amount, and the colour, and roughly how many pads. Photograph the pad if that is easier than describing it
Keep any tissue you pass. It can be sent for testing and it can answer questions nothing else will
Do not put anything in the vagina — no tampons, no douching, no sex until you have been told it is fine
Do not take ibuprofen, naproxen, or aspirin unless we prescribed low-dose aspirin. Paracetamol (acetaminophen) is fine for pain
Do not wait for the bleeding to stop to decide whether it was serious. Bleeding from an abruption or an ectopic can pause

Bed rest is not a treatment. It does not prevent miscarriage and it does not stop an abruption. Rest if you feel unwell, but do not let lying down substitute for being seen.

Things that do not cause bleeding

Readers arrive at this article carrying blame, so let us be specific. In an otherwise normal pregnancy, none of the following cause miscarriage or bleeding: sex, orgasm, moderate exercise, lifting your other child, air travel, an argument, stress, a scare, a fall on your bottom, hair dye, or a cup of coffee. Miscarriage in the first trimester is overwhelmingly chromosomal and was determined before you knew you were pregnant.

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Medical disclaimer

This article is general health information, not medical advice for any individual. Bleeding in pregnancy always warrants prompt evaluation: heavy bleeding, bleeding with severe one-sided or shoulder-tip pain, any bleeding after 20 weeks, bleeding with fever, or bleeding with faintness means go to the emergency department or labour and delivery immediately. In an emergency, call 911.