A registered nurse with more than 25 years of experience in oncology, labor/delivery, neonatal intensive care, infertility and ophthalmology, Sharon Perkins has also coauthored and edited numerous health books for the Wiley "Dummies" series.Perkins also has extensive experience working in home health with medically fragile pediatric patients.Before the advent of routine ultrasound in pregnancy, medical personnel estimated a baby’s due date by the date of the last menstrual period and by feeling the uterus and determining the size to see if it matched the given due date.With transvaginal ultrasound, checking for embryonic development known to occur within a certain time frame more accurately dates a pregnancy.Transvaginal ultrasound can see embryonic development about a week before transabdominal ultrasound, the American Pregnancy Association (APA) states.A transducer, a wand-shaped probe, is inserted into the vagina and pressed against the vaginal walls directly next to the uterus.It records high-frequency sound waves that create an image (see Reference 4).Normally, ultrasounds before until week 4 of pregnancy shows nothing in the uterus and serve no purpose.
At 4.5 to 5 weeks, a gestational sac may be seen in the uterus using transvaginal ultrasound, Joseph Woo, M.
D., explains in "Obstetric Ultrasound: A Comprehensive Guide".
Seeing the gestational sac, which looks like a black dot in the uterus, has several benefits: it confirms that a woman is pregnant, confirms that the pregnancy at a very early stage, making dating the pregnancy very accurate, and also confirms that the pregnancy is in the uterus rather than ectopic, or outside the uterus.
A yolk sac, the early source of nutrients for the embryo is seen around 5.5 to 6 weeks.
The embryo still can’t be seen at all at this early stage.