Bleeding during pregnancy: What you need to know

“I was standing on the porch of my parents’ house when a little pool of blood started to form at my feet,” says Charlene Morris, a mom of two in Dawson Creek, BC. She was five weeks pregnant with her second child, Felix, now 11 months. After passing a large clot and checking it for tissue (as a maternity nurse, Morris knew what to do), the bleeding fortunately slowed down. Her parents live in a small town, and she knew she wouldn’t be able to get an ultrasound so late at night. “It was 11 o’clock, so I lay down, tried to relax and waited until morning to have my mom take me to the ER,” she says. “Luckily, the ultrasound and blood tests showed everything was just fine.”

Light bleeding during the first 12 weeks of pregnancy is common and doesn’t usually signal a problem. The main cause of spotting in the first trimester is implantation bleeding. It occurs very early on—even before you may know you’re pregnant—as the egg implants in the lining of the uterus. At this stage spotting can also occur following sex (because the cervix is tender) or due to a pelvic or urinary tract infection. If it lasts for more than a few days or is more than a small amount when you wipe, see your doctor. In the meantime, don’t use tampons or have sex until the spotting stops.

Heavy bleeding during the first trimester, however, can signal a miscarriage. “If it’s accompanied by abdominal cramping or back pain, and you notice tissue passing through the vagina with the blood, see your doctor or head to the ER as soon as possible,” says Jon Barrett, chief of maternal and fetal medicine at Sunnybrook Health Sciences Centre in Toronto. An ectopic pregnancy (where the fertilized embryo implants outside of the uterus, usually in the fallopian tube) can also cause bleeding. This condition can be serious if it develops enough to rupture the tube, but this outcome is rare and the condition itself only occurs in less than two percent of pregnancies.

Melanie Baker, a mom in Brampton, Ont., recently experienced another rare condition called a molar pregnancy, when the embryo doesn’t develop properly, and the tissue becomes an abnormal growth instead. Baker knew she was pregnant and heard the heartbeat at 13 weeks, but by 17 weeks things changed. “I was spotting and had severe pain in my upper abdomen. I didn’t realize the two were connected and thought the pain was my gallbladder at first,” she says. An ultrasound and blood tests confirmed gestational trophoblastic disease (GTD), and a few days later the abnormal tissue was removed in hospital. If not caught early, GTD can lead to serious complications, including a rare form of cancer.

During the second half of pregnancy, bleeding can be caused by a placental abruption (where the placenta partially detaches from the uterine wall), though in most cases it doesn’t pose a danger to mother or child, says Barrett. Bleeding may also be caused by placenta previa (where the placenta partly or completely covers the cervix), which can be risky if it continues into the third trimester.

Jody Swanson, a mom of three in St. Albert, Alta., is currently on hospital bed rest with her fourth pregnancy. Heavy bleeding at 24 weeks sent her to the hospital where an ultrasound confirmed placenta previa. At 28 weeks she had another major bleed and was admitted for the duration of her pregnancy.

Spotting during the final weeks of pregnancy is typically a sign of labour. In this case you may you also see evidence of the mucous plug (cervical discharge that is sometimes clear and/or bloody) and experience a dull backache, stomach cramps or a sensation of uterine tightening. If you’re not yet 37 weeks, it’s considered preterm labour and you should contact your practitioner right away.

Whatever your stage, don’t panic if you see a little blood. “Light spotting can be normal at all stages, but if you’re unsure call your doctor to be safe,” says Barrett.

A version of this article appeared in our November 2014 issue with the headline, "Seeing red", p. 49.

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