Referral Timing Guide

Preferably in the early proliferative phase i.e. days 4 – 10 of the cycle (the endometrium is thinnest and more easily assessed at this time)
For women with irregular bleeding anytime apart from their heaviest days of bleeding (to avoid obscuring views of the uterine cavity)

Anytime if not on HRT
Temporary withdrawal of HRT at least 10 days prior to the scan minimizes any exogenous effects on the endometrial lining

The early proliferative phase of the cycle is best for avoiding confusion of a previous cyst with an active corpus luteum in the present cycle

Embryonic heart may be detected from as early as the sixth week however establishing embryonic life may not bepossible until the seventh week

Anytime once there is a positive B-hCG. Menstrual data is unreliable in diagnosing ectopic pregnancies and a quantitative B-hCG level is extremely useful as a diagnostic criteria (the absence of an intrauterine gestation sac once this level has reached 1000iu/l is highly suspicious for an ectopic unless proven otherwise).

The ultrasound scan for the nuchal translucency risk assessment is done in the 11 – 14 week window. Risk assessment may not be possible outside of this time frame depending on the fetal length (CRL).
For the Combined First Trimester screening programme the maternal serum can be drawn between 10 – 13 weeks. It is strongly recommended that the maternal serum be obtained at least one week prior to the scan to expedite the combined risk results from the central VCGS laboratory once the ultrasound data is sent in.

May be scheduled electively from 15 weeks gestation onwards
For diagnostic testing of abnormal mid-trimester findings, an urgent counseling and amniocentesis may be requested with rapid analysis (FISH) results available in 24 – 36 hours. Full results will take up to two weeks.