Diverse mechanisms underlying the fetal growth course in gastroschisis and omphalocele

Abstract

Gastroschisis and omphalocele are the two most common congenital fetal abdominal wall defects (AWDs). Both malformations are commonly associated with small for gestational age (SGA) neonates. However, the extent and causes of growth restriction remain controversial in both gastroschisis and omphalocele without associated malformations or aneuploidy. Aim of our study was to examine the role of the placenta and the birthweight:placental weight ratio (bw:pw ratio) in fetuses with AWDs. We included all cases of AWDs examined at our hospital between January 2001 and December 2020 retrieving the data from the hospitals software. Fetuses with any other combined congenital anomalies, known chromosomal abnormalities or lost to follow-up were excluded. In total, 28 singleton pregnancies with gastroschisis and 24 singleton pregnancies with omphalocele met the inclusion criteria. Patient's characteristics and pregnancy outcomes were reviewed. The primary outcome was to investigate the association between the birthweight and placental weight in pregnancies with AWDs as measured after delivery. In order to correct for gestational age and to compare total placental weights, ratios between the observed (O) and the expected (E) birth weight for the given gestational age in singletons were calculated. The scaling exponent β was compared to the reference value of 0.75. Statistical analysis was carried out using GraphPad Prism v8.2.1 (GraphPad Software, San Diego, CA, USA) and IBM SPSS Statistics25. A P-value < 0.05 indicated statistical significance. Women pregnant with a fetus with gastroschisis were significantly younger and more often nulliparous. Additionally in this group, the gestational age of delivery was significantly earlier and almost exclusively per caesarean section. Approximately half of the children were born SGA 46.7% (13/28) and only 3 (10.7%) had a placental weight <10%ile. There is no correlation between birthweight percentiles and placental weight percentiles (p=ns). However in the omphalocele group, 16.7% (4/24) of the children were born SGA (<10th centile) and all of them also had a placenta <10th centile. There is a significant correlation between birthweight percentiles and placental weight percentiles (p<0.0001). The bw:pw ratio differs significantly between pregnancies diagnosed with gastroschisis compared with pregnancies diagnosed with omphaloceles with 4.48 [3.79-4.91] versus 6.05 [5.38-6.47] (p<0.0001). Allometric metabolic scaling revealed that both gastroschisis and omphalocele placentas do not scale with birth weight. Fetuses with gastroschisis display impaired intrauterine growth, which seems to differ to the classical placental insufficiency growth restriction.