Thanks for your query
(FP) refers to a prominence / dilatation or the renal pelvis
Fetal pyelectasis can be a relatively common finding in an antenatal ultrasound
scan, often detected at the routine 2nd trimester morphology scan. It affects male fetuses more . The estimated prevalence is at ~ 2% of routine second trimeter scans
Pyelectasis can result from a number of factors. In the majority of cases, it is physiological and resolves spontaneously, so you need not worry too much.
However, it may also herald the presence or evolution of renal tract pathology, such as :
fetal PUJ obstruction
fetal VUJ obstruction
- e.g. posterior urethral valves
Associations with trisomy
21: presence and strength of this association is currently under debate and at best considered very mild.
Following are the cut off values for defining prominent fetal renal pelvis :
> 4 - 4.5 mm at 18 - 20 weeks (i.e. the routine 2nd trimester)
> 5 mm at ~ 20 - 29 weeks
> 6 mm at 32 weeks
persistent fetal pyelectasis : > 7 mm in the 3rd trimester
The vast majority of cases (~ 96%) with mild pyelectasis in the second trimester resolve, either during pregnancy
itself or in the early postnatal period, however serial monitoring with ultrasound is the best approach, you need to worry if there is
increasing degree of pelvic dilatation
Please act in concert with your treating obstetrician and also seek the opinon of a pediatric surgeon, or a neonatologist, who would also guide you accordingly . Your case is borderline ( very mild ) as the cut off values suggest.
Please dont worry.