Big head of foetus in womb-Why How to deliver safe?

Soft Markers in USG

Isolated Ventriculomegaly:  -Defined only when the AP diameter of posterior horns of  lateral ventricles  at the level of thalami are > 11 mm , unaccompanied by continuous production  of excess CSFà> therefore no resultant hydrocephalus which is excessive production  of  CSF.. Ventriculomegaly is observed in many CNS abnormalities. Isolated ventriculomegaly:- little importance : Need follow up : :  If limited to 15 mm then minimal concern. But if the AP diameter exceeds 15 mm then following possibilities exist e.g.1) Additional structural abnormalities of brain   2) congenital viral infections.. Defined as the lateral ventricle atria width at the level of parieto-occipital fissure. Of concern if more than 10 mm. whenever it is detected in utero, it is important to assess the extent and degree as well as any associated CNS or extra CNS anomalies. Ventriculomegaly is defines as -mild-(10-15mm) and severe > 15mm. It is a presenting feature of many abnormalities that have a wide spectrum of prognosis from very good to lethal.

Which soft markers are relevant? When to refer to foetal medicine unit?

Is serum markers too are positive? Then referral is a must, however insignificant is the soft markers may appear.  Referral to foetal medicine specialist is recommended & for aneuploidy counselling. This is also true for 1) increased NT above 6 mm, 2) dilated renal pelvis > 7mm, 3)  ventriculomegaly > 10mm. 4) echogenic bowel (same density as  bones).  ALL SUCH SOFT MARKERS à mandate aneuploidy  counselling. But if serum markers too are positive then obviously USG detected any soft markers (of minimal concern)   have some relevance in such cases referral to foetal medicine expert.

Which soft markers are innocouos and do not warrant referral?   1) Dilated cistern Magna,2) Echogenic foci on the heart   3) two vessel cord.

What is the detection rate of structural malformation?

Obesity is an impediment to have clear picture of foetus and therefore in DM cases many a malformation are missed. Even by experts. The detection rates are in the range of severe cardiac malformation (50% only), Skeletal dysplasia (DR= 60% only i.e. 40% are missed),cleft lip (75%), Diaphragmatic hernia(60%) and Exomphalos and bilateral Renal agenesis are detected in 80% only and 20% of such anomalies are missed!! Similarly in 10% cases of OSD is missed. But detection rate is high95-98% in cases with Anencephaly, Gastroschisis, Trisomy 13(Patau syndrome) & trisomy 18(Edwards). Further, many anomalies are missed due to late appearance of those CM.

Should we routinely perform anomaly scan to all low risk women even if first trimester sac &srum markers are negative? –At UK-yes. Better just after 20 weeks so that organs could be visualized properly. So also Foetal Echo.(Foetal Medicine Book-Cameron).The prevalence of structural anomalies is a follows:- in pregnancy(2-3%), Of al still births(10%),of all NND(as many as 25%).

Hydrocephalus. : Classification of hydrocephalus.

- This term is reserved for cases where a) there is continued excessive production of CSF in the lat ventricles  or   b) Obstruction in the drainage system of CSF-Aqueduct  stenos is Obstructive hydrocephalus.

3) Aqueductal Stenos is. - Cause, Treatment and Recurrence Risk.

A)     X- linked / autosomal recessive genetic cause,

B)      Rec. Risk is 2 %( see pp. 1530- Book No. FOGSI -First USG Book).

C)      Measurements and Diag, - Lat ventricles are usually measured from midline to lat border.

Also measured is the corresponding hemisphere. Then a ratio is calculated called LVHW (Lat ventricle: corresponding hemisphere width). This ratio is normally-71% upto 18 weeks and later reduced to 33% after 18 weeks. The sequence of dilatation is post horn, then body and lastly Ant horns. There is usually no dil of Th. Borderline ventriculomegaly may resolve and may have no consequence in vast majority of cases. But even isolated borderline ventriculomegaly has an abnormal outcome in 20 percent cases with a 4 percent risk of perinatal death and another 4 percent having chromosomal aberrations.

Severe ventriculomegaly is often a result of obstruction to CSF flow at some level. In these cases the level of obstruction needs to be identified as well as the cause of obstruction. The cortical thickness also affects the prognosis.

The cases with mild ventriculomegaly are more often associated with chromosomal defects and hence warrant a detailed sonographic examination to look for other detectable stigmata of various syndromes. The risk of Aneuploidies may be as high as 36 percent in presence of associated malformations.

The risk of non chromosomal syndromes like Miller-Dicker, Goldenhar, Meckel-Gruber and many others is also high.

A FETUS WITH VENTRICULOMEGALY SHOULD ALWAYS UNDERGO KARYOTYPE and MOTHER SHOULD BE SCREENED FOR INFECTIONS.

What are the possibilities of CM in following conditions?

1)1f F/H/O NTD or CHDTop of Form

:- 5% chance 2) F/H.O Cleft lip:-4% 3) H/O consumption of Anticonvulsant :-5% 4) CMV:- 25% 5) Twin gestation:- 3%.