A twin pregnancy, medically known as a multiple gestation, involves carrying two or more fetuses simultaneously. Supporting two developing babies places greater physical demands on the body compared to a singleton pregnancy. While all pregnancies can involve spotting or bleeding, a twin pregnancy often increases the likelihood and complexity of these occurrences. Understanding the various sources of bleeding is important, as some causes are common to all pregnancies while others relate directly to the presence of two placentas or embryos.
Common Sources of Early Pregnancy Bleeding
Bleeding in the first trimester is frequent and often related to factors not unique to carrying twins. Implantation bleeding is light spotting that happens about one to two weeks after conception as the fertilized embryo embeds itself into the uterine wall. This type of bleeding is typically minimal and brief, sometimes mistaken for a light period.
Another common source is cervical irritation. Pregnancy hormones increase blood flow to the cervix, making the tissue more sensitive. Minor trauma, such as sexual intercourse or an internal pelvic examination, can easily trigger light spotting from the highly vascularized cervix.
A subchorionic hematoma is a blood clot that forms between the uterine wall and the chorion, the outer membrane surrounding the developing fetus. This is considered the most common reason for first-trimester bleeding and can range from light spotting to heavier flow. Although not exclusive to twin pregnancies, many smaller hematomas resolve completely without complications.
Bleeding Linked Specifically to Multiple Gestation
The presence of two fetuses introduces unique sources of bleeding that are significantly more common in multiple gestations.
Vanishing Twin Syndrome (VTS)
VTS occurs when one fetus fails to develop and is reabsorbed by the mother or the surviving twin, usually in the first trimester. VTS is estimated to occur in about 36% of twin pregnancies. The reabsorption process can result in vaginal bleeding or spotting as the body expels the non-viable tissue.
Placenta Previa
Twin pregnancies carry a higher risk of complications related to placental position. The enlarged surface area required for two placentas increases the likelihood of placenta previa, where the placenta partially or completely covers the cervix. This condition is a known cause of painless, bright red bleeding, especially in the second and third trimesters. Dichorionic twin pregnancies are at a significantly increased risk compared to singleton pregnancies.
Placental Abruption
The increased stretching of the uterus necessary to accommodate two growing babies can raise the risk of placental abruption. Abruption is the premature separation of the placenta from the uterine wall before delivery, causing severe, painful bleeding. Twin pregnancies face a relative risk of placental abruption approximately 2.2 times greater than in a singleton pregnancy. This risk is often compounded by the higher incidence of complications like pre-eclampsia.
When to Seek Emergency Medical Attention
While light spotting is common in early pregnancy, any vaginal bleeding in a multiple gestation should be reported to a healthcare provider for proper evaluation. Immediate medical attention is necessary if the bleeding becomes heavy, defined as soaking two or more sanitary pads within an hour. Heavy bleeding accompanied by the passing of large blood clots or tissue requires urgent assessment to rule out severe complications.
Warning signs that signal a medical emergency include:
- Severe, persistent abdominal pain or intense cramping that does not subside.
- Dizziness or feeling faint.
- A fever of 100.4°F or higher, or chills, as these can indicate significant blood loss or infection.
The medical evaluation will typically involve an ultrasound to confirm the location of the pregnancy, assess the status of both fetuses, and identify the source of the bleeding, such as a placental issue. A physician may also perform a cervical examination to check for irritation or an open cervix, along with blood tests to measure human chorionic gonadotropin (hCG) and confirm stability. Depending on the diagnosis, management may range from simple monitoring to recommendations for bed rest and pelvic rest. Timely diagnosis is important for managing twin pregnancy complications.