…..Over the last 30 years, ultrasound has changed dramatically in how we evaluate early pregnancy. Transvaginal sonography has allowed us to assess early gestation with better clarity.
…..The gestational sac is the first visible sign of a normal
intrauterine pregnancy. This should be seen with the transvaginal sonogram by 5 weeks after the last menstrual period. The earliest embryonic structure is the yolk sac, and likewise, this can be seen as early as the end of the 5th week. Evaluating the yolk sac is important because it can point to problems in a pregnancy. If it is not present at this early time, or if the shape is irregular or large, this can be the first sign of a nonviable pregnancy.
…..Near the 6th week from the last menstrual period, the embryo should be seen attached to the yolk sac, and fetal heart activity should be noted between the 6th and 7th week. When the gestational sac is approximately 2 cm, an embryo should be seen, and if it is not identified at this time, a blighted ovum is confirmed.
…..There are specific sonographic signs of a problem pregnancy:
- A small gestational sac around the embryo
- If the embryo does not increase in size by 1 mm per day
- A fetal heart beat at a rate of less than 120 beats per minute after 7 weeks of gestation.
…..Let us end this review on a positive note. If a patient has no abnormal symptoms, normal fetal heart activity, and 7 weeks of gestation has been reached, then there is a 99% chance of a successful pregnancy.
…..There are a few common causes of bleeding in the first trimester:
- Spontaneous abortion
- Ectopic pregnancy
- Subchorionic hemorrhage
- Gestational trophoblastic disease (less common)
…..When we speak about miscarriages (spontaneous abortions), there are a few terms which are frequently used. An ultrasound and an examination will usually confirm the diagnosis:
- Threatened abortion (when vaginal bleeding occurs before 20 weeks of gestation, there is a viable pregnancy, and the woman has a closed cervix)
- Inevitable abortion (if there is a dilated cervix)
- Incomplete abortion (when a portion of the pregnancy has passed)
- Complete abortion (when all of the pregnancy tissue (products of conception) has passed)
…..Gestational trophoblastic disease is a much less common cause of vaginal bleeding early in a pregnancy. Some signs of this condition would be a pregnancy size larger than would be expected (based on routine dates), very high levels in a blood pregnancy hormone test (hCG), and severe nausea and vomiting. Here are some common terms that are encountered:
- Complete hydatidiform mole: A partial mole is formed when a sperm fertilizes an egg that has no nucleus. This is the most common type of this condition. On a sonogram, there may be many ovarian cysts seen or many cysts within the uterus.
- Partial mole: This arises when two sperm fertilize an egg. On a sonogram, there may be a sac with a fetus.