First trimester vaginal bleeding is quite common. About 20-25% of pregnant women will bleed or spot in the first trimester. Spotting can occur 6-12 days after pregnancy ensues due to implantation of the zygote (fertilized egg) in the endometrial lining (the tissue inside the uterus).
There can, of course, be other causes for the vaginal bleeding. The most common is a threatened miscarriage. If you have first trimester bleeding, your provider will most likely order an ultrasound to look at the pregnancy. Be aware, however, that the pregnancy is difficult to see on ultrasound prior to six weeks gestation. He will also order serial quantitative B-HCGs d(human chorionic gonadotropin). The quantitative B-HCGs will allow your provider to see if your pregnancy hormone levels are increasing, decreasing, or plateauing. The quantitative B-HCG value should increase by roughly 50% every 48 hours in the early stages of pregnancy. If your numbers are increasing appropriately, then the pregnancy most likely is doing well. Your provider will probably recommend bed rest and pelvic rest. If the numbers are decreasing, then the pregnancy is not doing well, and you may be in the process of having a miscarriage. The same applies if the pregnancy numbers are plateauing. If a diagnosis of inevitable miscarriage (spontaneous abortion or SAB) is made, then your provider may recommend either a dilation and curettage (D&C) or expectant management if it looks like your body is passing the products of conception (POC) on its own. A threatened or actual miscarriage can be accompanied by mild to severe uterine cramping along with moderate to severe vaginal bleeding.
A blighted ovum is a condition where the pregnancy fails to develop, and can also present with first trimester vaginal bleeding. The ultrasound will show an empty yolk sac, and the quantitative B-HCG values will either decrease or plateau. Your provider may recommend a D&C or expectant management for this entity as well.
A plateauing or up and down quantitative B-HCG may also signify an ectopic pregnancy. An ectopic pregnancy is where the pregnancy implants outside the uterus. The pregnancy can implant in the fallopian tube most commonly, and less commonly in the juncture where the fallopian tube joins the uterus (cornual pregnancy). In this case, the ultrasound will not detect an intrauterine pregnancy even at the expected time of six weeks. With today’s sophisticated ultrasound machines, the pregnancy may be visualized in the fallopian tube along with fluid in the cul-de-sac (the area between the inferior posterior aspect of the uterus and the rectum). A cornual pregnancy may sometimes be mistaken for an intrauterine pregnancy. The danger to the patient is rupture of the ectopic pregnancy which can lead to internal hemorrhaging and death. Rupture will usually take place around 4-6 weeks, but can happen later as in the case of the cornual pregnancy where rupture can occur as late as the early second trimester.
The objective with an ectopic pregnancy is to address the issue prior to rupture of the fallopian tube. If your provider is suspicious of this entity, he will most likely recommend a laparoscopy under general anthesia where he makes two or three small incisions on your abdomen and then inserts a tube with a lens on one end and a light on the other which will allow him to make the diagnosis. Depending on the clinical presentation of the ectopic, he may perform a salpingostomy (a linear incision is made on the antimesenteric side of the tube, and the pregnancy removed while saving the tube) or he may elect to perform a salpingectomy (remove the affected fallopian tube) or partial salpingectomy (remove a portion of the affected fallopian tube). Other factors will enter into your treatment decision like your desire to have more pregnancies or not. Another treatment option besides surgery is to use methotrexate (an anticancer drug) which will eliminate the pregnancy by killing the trophoblasts (pregnancy tissue) followed by absorption of the tissue by your body. Your provider will discuss the different treatment options with you.
Occasionally, there are some pregnancies where vaginal bleeding starts in the first trimester, and then continues throughout the pregnancy without a definite diagnosis. When I was practicing, I saw one such case where the etiology was never found. The pregnancy went to term with an uneventful delivery. The placenta looked normal on gross inspection, and the reason for the bleeding never discovered.
Other causes of vaginal bleeding can include cervical or endocervical polyps (growths on the cervix or the cervical canal respectively), venereal warts, cervicitis (inflammation of the cervix), or vaginitis (inflammation of the vagina).
Rarely, there will be other etiologies for the first trimester vaginal bleeding. Entities like cervical cancer and hydatidiform mole can cause vaginal bleeding. But, again, let me emphasize that these entities are rare.
You should inform your provider if you experience first trimester vaginal bleeding. He will examine you and order blood work and imaging tests to help make the diagnosis.
Wishing you a successful pregnancy and delivery, Pablo.