First-trimester bleeding

If you experience vaginal bleeding at any time during pregnancy, report it to your health professional immediately. Vaginal bleeding can be a sign of miscarriage or premature labor during a pregnancy but sometimes it is not, particularly in the first trimester.

During the first trimester of pregnancy:

• Up to 25% of pregnant women experience spotting to heavier vaginal bleeding. Of these women, about 50% do not miscarry.¹ Vaginal bleeding during pregnancy is more common in women who have previously been pregnant than in women who are pregnant for the first time.
• Very early spotting is sometimes the result of the fertilized egg implanting in the uterus. Implantation takes place 6 to 10 days after the sperm fertilizes the egg.
• Bleeding can be a sign of miscarriage. Early bleeding during the first 6 weeks or so can be an early miscarriage called a blighted ovum. Although a gestational sac has developed, the fertilized egg has not developed into an embryo. This is usually caused by a chromosomal error in the early stages of cell formation. On an ultrasound, a blighted ovum is likely to look like an empty sac attached to the uterine wall.

Citations

1. Cunningham FG, et al. (2005). Abortion. In Williams Obstetrics, 22nd ed., pp. 231–251. New York: McGraw-Hill.