Vaginal bleeding during pregnancy is common but should not be considered normal. Approximately 25% to 40% of women will experience bleeding at some point from the time of conception until delivery.
Bleeding does not always mean there is a problem, but it can be a sign of miscarriage or other complications. Becoming familiar with the causes of bleeding will help you know when to contact your doctor.
Bleeding in first trimester (< 12 weeks)
The most common time to experience bleeding is in the first trimester. Most women who have bleeding early in pregnancy go on to have healthy babies. However, heavy bleeding and bleeding that lasts for days can be a sign of a problem and should be evaluated. Possible causes of bleeding include:
Embryo implanting. Light bleeding in the first few weeks after conception may be a sign that the embryo is implanting into the uterus which is a normal process. The term spotting is also used which means light bleeding. It’s less than a period and could last from a few hours to a few days.
Miscarriage. The biggest concern regarding bleeding early in pregnancy is a miscarriage. Miscarriages occur in 15% to 20% of all pregnancies so bleeding that is heavy, more than a period or lasts for more than a few days, should be evaluated to make sure the pregnancy is progressing normally. Half of patients with bleeding in the first trimester will miscarry. A miscarriage is diagnosed with an ultrasound exam to look for the fetal heartbeat.
Ectopic pregnancy. This occurs when the embryo implants outside of the uterus, usually in the fallopian tube. Ectopic pregnancy occurs in only 2% of pregnancies but can be a life-threatening condition. If the embryo keeps growing within the tube, it can rupture and cause serious bleeding. The diagnosis is made with an ultrasound exam and checking pregnancy hormone levels. An ectopic pregnancy is highly likely if the pregnancy is not seen in the uterus with a vaginal ultrasound exam at 5-½ to 6 weeks and your hCG hormone level is 2,000-3,500 IU/L. This condition requires immediate treatment with medication or surgery.
Subchorionic hemorrhage. A small blood clot that collects under the placenta or membranes is called a subchorionic hemorrhage. This is seen with an ultrasound exam and can explain vaginal bleeding at any gestational age. Depending on its size, this can be a risk factor for miscarriage or early rupture of the membranes and preterm labor.
Infection. Infections of the cervix and vagina can cause irritation that results in spotting. This is evaluated with a speculum exam and by checking cultures to determine if treatment is necessary.
Bleeding from the cervix. Pregnancy hormones can cause the cells on the cervix to be sensitive to touch and movement, which can result in spotting. This is a common cause of light spotting in pregnancy and can occur when the cervix is touched during sex, a speculum exam, pelvic exam or from a pap smear.
Molar pregnancy. This is when abnormal placental tissue forms in the uterus instead of an embryo. It is a rare condition but requires attention to prevent complications. It is diagnosed with ultrasound and a pregnancy hormone level.
Bleeding in second & third trimesters (13-42 weeks)
Bleeding later in pregnancy is more serious and should usually be evaluated by your doctor. Possible causes include:
Cervical insufficiency. The cervix can sometimes open early in pregnancy and result in a very preterm birth. This is called cervical insufficiency because the cervix becomes weak and does not hold the baby in the uterus. Often patients are not aware this is happening or have only a small amount of spotting or pressure. Early dilation or shortening of the cervix can be treated with progesterone or a cerclage procedure. A cerclage involves putting a stitch into the cervix to hold it closed.
Preterm labor. Vaginal bleeding can occur with contractions and dilation of the cervix. If you are having painful contractions that occur every five to 10 minutes or more, spotting or bleeding, and you are early in the pregnancy (< 37 weeks), you should be evaluated for preterm labor. You will be placed on a monitor to determine if you are contracting and your cervix will be checked. Preterm labor at less then 35 weeks gestation can be treated with medications to stop labor and steroids to improve the lung maturity of our baby.
Miscarriage. A miscarriage or fetal loss can also occur later in pregnancy. Sometimes patients will notice a decrease in fetal movement or just have bleeding. An ultrasound can be done to evaluate the heartbeat and movements.
Placenta previa. If the placenta implants over the cervix, this can result in bleeding late in pregnancy when the cervix moves or dilates. This type of bleeding usually occurs without any pain and is easily diagnosed with an ultrasound to look at where the placenta is located. This is a serious condition that can lead to heavy bleeding and risk for the mom and baby. A C-section is required for delivery because the placenta covers the birth canal.
Placenta abruption. This is when the placenta detaches from the wall of uterus causing blood to collect between the placenta and uterus. It is usually accompanied by abdominal pain and cramping. Because of the risks, hospital admission is needed to monitor the baby and mom and early delivery may be necessary.
Types of tests to expect
Depending on the amount of bleeding and your gestational age, the following tests are used to determine the cause of your bleeding.
Ultrasound exam. One of the first steps in evaluating bleeding in pregnancy is an ultrasound exam. This is done to confirm that the pregnancy is in the uterus (not ectopic) and that there is a normal heart beat (no miscarriage). Ultrasound will also determine placenta location, evidence of blood clots and the length of the cervix.
Pregnancy hormone level. A pregnancy hormone level (hCG) is often checked in early gestation (< 6 weeks) to determine if you are pregnant and, before the embryo is seen by the ultrasound, if the pregnancy is progressing normally. Repeated hCG levels are helpful only during the first six weeks of pregnancy. After an ultrasound has confirmed that the embryo is within the uterus, there is no benefit in checking serial hCG levels. Other hormone tests like progesterone and estrogen are not useful in confirming a normal pregnancy.
Speculum exam. With a speculum exam, the cervix can be visualized to find out if the bleeding is coming from a pelvic infection, a mass on the cervix, a cervical laceration, or dilation of the cervix.
When to call your doctor
Because bleeding at any time in pregnancy can be a sign of a problem, you should always let your doctor or midwife know when it occurs and how heavy your bleeding is. Light bleeding or spotting lasting hours or less than a day can be discussed within 24 hours.
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- What to expect the first trimester of pregnancy
- 10 things to expect in your second trimester