As long as interval fetal growth and fetal surveillance test results are normal, pregnancy is allowed to continue until fetal lung maturity is reached (see Fig. 44-9). Reassessment of fetal growth is typically made no sooner than 3 to 4 weeks. Weekly assessment of umbilical artery Doppler velocimetry and amnionic fluid volume is combined with periodic nons tress testing, although the optimal frequency has not been determined. As mentioned, we hospitalize these women in our High-Risk Pregnancy Unit and monitor their fetuses daily. If interval growth, amnionic luid volume, and umbilical artery Doppler velocimetry are normal, then the mother is discharged home and seen intermittently for outpatient surveillance.
With growth restriction remote from term, no speciic treatment ameliorates the condition. For example, evidence does not support diminished activity or bed rest to accelerate growth or improve outcomes. Despite this, many clinicians intuitively advise a program of modiied rest. Nutrient supplementation, attempts at plasma volume expansion, oxygen therapy, antihypertensive drugs, heparin, and aspirin are all inefective (American College of Obstetricians and Gynecologists, 2015).
In most cases diagnosed before term, neither a precise etiology nor a specific therapy is apparent. Management decisions hinge on assessment of the relative risks of fetal death during expectant management versus the risks from preterm delivery. lthough reassuring fetal testing may allow observation with continued maturation, long-term neurological outcome is a concern (Baschat, 2014; Lees, 2015; Thornton, 2004). Baschat and associates (2009) showed that neurodevelopmental outcome at 2 years in growth-restricted fetuses was best predicted by birthweight and gestational age. Doppler abnormalities are generally not associated with poor childhood cognitive developmental scores among low-birthweight fetuses delivered in the third trimester (Llurba, 20l3). hese indings emphasize that adverse neurodevelopmental outcomes cannot always be predicted.
Fetal-growth restriction is commonly the result of placental insuiciency due to faulty maternal perfusion, reduction of functional placenta, or both. If present, these conditions are likely aggravated by labor. Equally important, diminished amnionic luid volume raises the likelihood of cord compression during labor. For these and other reasons, the frequency of cesarean delivery is increased. Accordingly, a woman with a suspected growth-restricted fetus should undergo "high-risk" intrapartum monitoring (Chap. 24, p. 478).
The risk of neonatal hypoxia or meconium aspiration is also greater. hus, care for the newborn should be provided immediately by an attendant who can skillfully clear the airway and ventilate a neonate as needed (Chap. 32, p. 608). he severely growth-restricted newborn is particularly susceptible to hypothermia and may also develop other metabolic derangements such as hypoglycemia, polycythemia, and hyperviscosity. In addition, low-birthweight newborns are at higher risk for motor and other neurological disabilities. Risk is greatest at the lowest extremes of birth weight (Baschat, 2009, 2014; Llurba, 2013).
The term macrosomia is used rather imprecisely to describe a very large fetus or newborn. Although there is general agreement among obstetricians that neonates weighing < 4000 g are not excessively large, a similar consensus has not been reached for the definition of macrosomia. Newborn weight rarely exceeds 11 pounds (5000 g), and excessively large infants are a curiosity. The largest newborn cited in the Guinness Book of World Records was a 23-lb 12-oz (10,800 g) infant boy born in 1879 to a Canadian woman (Barnes, 1957).