**7.2. Delivery management**

Because amniotic fluid is predominantly composed of fetal urine, measurement of biochemical markers contained in amniotic fluid (fetal urine) can be used to assess fetal renal

• Follow-up assessment. Repeat antenatal ultrasound examinations are performed to help guide management decisions. The timing is dependent on findings on the initial examination. Fetuses with second trimester hydronephrosis (RPD >4 mm) should undergo repeat testing in the third trimester to assess progression and select those who will benefit most from postnatal testing. A repeat examination 2–3 weeks later in fetuses with bilateral involvement (or an affected solitary kidney) and at 32–34 weeks of gestation in those with

• In utero intervention. Although there have been case series of antenatal surgery in fetuses with severe hydronephrosis and oligohydramnios, this intervention has not been shown to improve renal outcome. These procedures may increase the amount of amniotic fluid, thus potentially improving lung development and survival rate. In these rare cases, the procedure should only be performed in select centers with expertise and in infants with severe bilateral hydronephrosis, absent of severe renal parenchymal or cystic disease, favorable urinary electrolyte levels and osmolality, and normal karyotype [84]. Data are limited on whether percutaneous vesicoamniotic shunting compared with conservative observation in fetuses with lower urinary tract obstruction improves survival and renal outcome. The percutaneous vesicoamniotic shunting should not be routinely performed in fetuses with

Cesarean delivery should be reserved for obstetrical indications. The time of delivery depends

Prenatal sonographic diagnosis of gastrointestinal atresia is challenging since obstruction may not become evident sonographically until the late second trimester, after the typical time of a fetal anatomic survey (18–20 weeks of gestation). It can also be difficult to differentiate dilated small bowel loops from colon or megaureters sonographically [86]. It is unclear whether prenatal diagnosis of esophageal, gastrointestinal, or anorectal atresia improves the prognosis. However, early prenatal diagnosis provides an opportunity for parental counseling and preparation, screening for associated anomalies, and the option for pregnancy termination or delivery at a setting with appropriate personnel and facilities for newborn

function [84].

unilateral involvement is recommended [85].

494 Congenital Anomalies - From the Embryo to the Neonate

lower urinary tract obstruction [85].

on the fetal well-being and amniotic fluid volume.

**7. Esophageal, gastrointestinal, and anorectal atresia**

**6.2. Delivery management**

**7.1. Pregnancy management**

care [86].

Atresia alone is not an indication for cesarean delivery in the absence of a standard obstetric indication. However, if the abdominal circumference is much larger than the head circumference, cesarean delivery should be considered due to the risk of fetal abdominal dystocia. Delivery should be planned at a center that has an appropriate level of neonatal support.
