When should you see a gestational sac

Usually by 5 weeks LMP (3 weeks post conception) a gestational sac will be visualized. However, virtually all clinicians know that menstrual dating is notoriously unreliable.

Therefore the concept of a discriminatory level of hCG was developed. The discriminatory level of hCG was originally described in 1981.6 The initial report was with transabdominal ultrasound and equalled 6500IU/L. This was updated in 1985 by Nyberg et al.7 to 3600 IU/L. Transvaginal ultrasonography led to the level being reduced to 1000 IU/L.8 Clearly this will depend on the type and frequency of the equipment used, its degree of magnification, as well as the presence of coexisting fibroids. Furthermore it can be affected by extreme maternal obesity, the uterus being in a poor scanning position (e.g. axial) and in the presence of a multiple pregnancy. The endometrium, while lacking a gestational sac should at least have an appearance compatible with an early normal pregnancy, that is lush, homogeneous and decidualized/secretory in appearance (see Figures 4.1, 4.2 and 4.3). Details of the management when a pregnancy sac cannot be seen in the uterus in the presence of a positive pregnancy test are outside the scope of this chapter (see Chapter 7).

NYU MEDICAL CENTER Bll*

LONG UTERUS

G S4

Figure 4.3 Longitudinal axis transvaginal ultrasound view of a woman whose last period was 5+6 weeks before but with a history of markedly irregular cycles. The woman had a 2-day history of vaginal spotting and a closed cervical os on physical examination. The home pregnancy test was positive. This appearance of the endometrial echo is at least compatible with an early ongoing intrauterine pregnancy that may just be below the level of the discriminatory zone. A report of 'no gestational sac seen' is inadequate in such cases. It is essential that the findings seem at least be compatible with an ongoing potentially viable intrauterine pregnancy.

Gestational Sac

Figure 4.4 Intrauterine gestational sac at 7 weeks. The mean gestation sac diameter was 28 mm. The failure to visualise a normal yolk sac is diagnostic of a definitively failed intrauterine gestation. A follow-up ultrasound scan or serial determination of hCG levels in such a case is unnecessary and inappropriate.

Figure 4.4 Intrauterine gestational sac at 7 weeks. The mean gestation sac diameter was 28 mm. The failure to visualise a normal yolk sac is diagnostic of a definitively failed intrauterine gestation. A follow-up ultrasound scan or serial determination of hCG levels in such a case is unnecessary and inappropriate.

NYU MEDICRL CENTER

BUt Q£

pee

7HHI

E721

^ . sémISB-"' *

. '/i ' ' ! \j*4

0R72 G S4

i? '

■*

My First Baby

My First Baby

Are You Prepared For Your First Baby? Endlessly Searching For Advice and Tips On What To Expect? Then You've Landed At The Right Place With All The Answers! Are you expecting? Is the time getting closer to giving birth to your first baby? So many mothers to be are completely unprepared for motherhood and the arrival of a little one, but stress not, we have all the answers you need!

Get My Free Ebook


Responses

  • Tesmi
    When should you see a gestational sac?
    7 years ago

Post a comment