Conditions associated with chronic uteroplacental hypoxia include preeclampsia, chronic hypertension, asthma, maternal cyanotic heart disease, smoking, and high altitude. When exposed to a chronically hypoxic environment, some fetuses have signiicantly reduced birthweight. In more than 1.8 million births in Austria, the birthweight declined 150 g for each 1000meter rise in altitude (Waldhoer, 2015). In 63,620 Peruvian live births, the mean birthweight was significantly decreased at higher compared with lower altitudes-3065 g ± 475 g versus 3280 g ± 525 g (Gonzales, 2009). In this study, the rate of birth weights <2500 g was 6.2 percent at low altitudes, and it was 9.2 percent at high altitudes. In contrast, the rate of birthweights >4000 g was 6.3 percent at low altitudes and 1.6 percent at high altitudes.
In most cases, maternal anemia does not restrict fetal growth. Exceptions include sickle-cell disease and some other inherited anemias (Desai, 2017; Thame, 2016). Importantly, curtailed maternal blood-volume expansion is linked to fetal-growth restriction (de Haas, 2017; Stott, 2017). This is further discussed in Chapter 40 (p. 718).
Adverse obstetrical outcomes including fetal-growth restriction have been associated with three species of antiphospholipid antibodies: anticardiolipin antibodies, lupus anticoagulant, and anti-32 gycoprotein-I antibodies. Mechanistically, a "wohit" hypothesis suggests that initial endothelial damage is then followed by intervillous placental thrombosis. More specifically, oxidative damage to certain membrane proteins such as 32 glycoprotein-I is followed by antiphospholipid antibody binding, which leads to immune complex formation and ultimately to thrombosis (Giannakopoulos, 2013). his syndrome is considered in detail in Chapters 52 (p. 1008) and 59 (p. 1143). Pregnancy outcomes in women with these antibodies may be poor and include fetal-growth restriction and fetal demise (Cervera, 2015). he primary autoantibody that predicts obstetrical antiphospholipid syndrome appears to be lupus anticoagulant (Yelnik,r2016).
It is controversial whether pregnancies in women with prior infertility with or without treatment have an increased risk of SGA newborns (Zhu, 2007). Dickey and colleagues (2016) compared birthweight curves for singletons conceived by in vitro fertilization to the birthweight curves of Duryea (2014), described on page 846. hey found no reduction in fetal growth. Kondapalli and Perales-Puchalt (2013) reviewed possible links between low birthweight and infertility with its various interventions and concluded that any association remains unexplained for singletons.
Placental, Cord, and Uterine Abnormalities