태아 성장 지연(Fetal growth retardation)

태아성장지연

-임신 주수에 비해 체중이 10percentile 미만

-small for-gestational-age (SGA) infants are those whose weights were below the 10th percentile for their gestational age.<Williams obstetrics>

Symmetrical Versus Asymmetrical Growth Restriction

Campbell and Thoms (1977) described the use of the sonographically determined head-to-abdomen circumference ratio(HC/AC) to differentiate growth-restricted fetuses. Those who were symmetrical were proportionately small, and those who were asymmetrical had disproportionately lagging abdominal growth. The onset or etiology of a particular fetal insult has been hypothetically linked to either type of growth restriction. In the instance of symmetrical growth restriction, an early insult could result in a relative decrease in cell number and size. For example, global insults such as from chemical exposure, viral infection, or cellular maldevelopment with aneuploidy may cause a proportionate reduction of both head and body size. Asymmetrical growth restriction might follow a late pregnancy insult such as placental insufficiency from hypertension. Resultant diminished glucose transfer and hepatic storage would primarily affect cell size and not number, and fetal abdominal circumference—which reflects liver size—would be reduced. Such somatic growth restriction is proposed to result from preferential shunting of oxygen and nutrients to the brain, which allows normal brain and head growth—so-called brain sparing. The fetal brain is normally relatively large and the liver relatively small. Accordingly, the ratio of brain weight to liver weight during the last 12 weeks—usually about 3 to 1—may be increased to 5 to 1 or more in severely growth-restricted infants. Because of brain-sparing effects, asymmetrical fetuses were thought to be preferentially protected from the full effects of growth restriction. Considerable evidence has since accrued that fetal-growth patterns are much more complex. Nicolaides and co-workers (1991) found that fetuses with aneuploidy typically had disproportionately large head sizes and thus were asymmetrically growth restricted, which was contrary to thinking at that time. Moreover, most preterm infants with growth restriction due to preeclampsia and associated uteroplacental insufficiency were found to have symmetrical growth impairment—again, a departure from contemporaneous thinking (Salafia and associates, 1995). More evidence was presented by Dashe and colleagues (2000), who analyzed 8722 consecutive liveborn singletons who had undergone sonographic examination within 4 weeks of delivery. Although only 20 percent of growth-restricted fetuses demonstrated sonographic head-to-abdomen asymmetry, these fetuses were at increased risk for intrapartum and neonatal complications. Symmetrically growth-restricted fetuses were not at increased risk for adverse outcomes compared with those appropriately grown. These researchers concluded that asymmetrical fetal-growth restriction represented significantly disordered growth, whereas symmetrical growth restriction more likely represented normal, genetically determined small stature. Finally, recent data from Holland further challenges the concept of “brain sparing.” Roza and associates (2008) provided follow-up of 935 toddlers enrolled between 2003 and 2007 in the Generation R Study in Rotterdam. Using the Child Behavior Checklist at 18 months of age, they found that infants with circulatory redistribution—brain sparing—had a higher incidence of behavioral problems.

<Williams obstetrics section 7>

preclampsia 태아의 IUGR에 대해 case 발표하다가 교수님꼐서 물어보셨습니다. 자, FGR일때 symmetrical하고 assymetrical하고 나누는데 각각이 무슨 의미지? 저는 열심히 책을 보고 공부를 했기 때문에 읽은 데로 대답을 해 보았죠. symmetrical한 경우는 cell수도 작고 크기도 작은 반면 assymetrical은 cell 수는 그대로인데 크기가 작은 것입니다!

하지만 교수님이 원한 건 그게 아니었죠. 그래서 아, symmetrical한 것은 초기에 문제가 발생한 경우가 많고 asymmetrical한 경우는 후반에 문제가 발생한 경우가 많습니다. 하지만 전자간증 산모의 태아의 경우 symmetrical한 경우를 보인다고 공부하였습니다.

 결국 교수님이 원하는 말을 하지 못했더랬죠. 전 항상 공부를 하면 그 속에서 가장 중요한 부분에 대한 이해가 부족한가 봅니다  교수님께서 가장 중요하게 생각하셨던 부분은 바로 Brain sparing 입니다. 

 assymetrical하다는 것은 머리둘레가 배둘레의 성장보다 비교적 크다는 의미이죠. 성장지연이라는 의미는 영양공급이 원활하지 않다는 것이고 따라서 에너지를 선택적으로 나눠 주게 되겠죠. 이는 우리가 쇼크가 왔을 때 혈액공급이 가장 우선적으로 보존되는 중요한 장기들에 피가 가는 것과 똑같은 패턴을 보이게 됩니다. 그 중에서 초음파로 가장 잘 보이는 것이 머리이죠. 그래서 head-to-abdomen circumference ratio(HC/AC)를 보게 됩니다.

 여튼, 애기한테 영양공급이 적어서 문제가 될 경우 머리만 상대적으로 크게된다. symmetrical한 경우는 유전적인 소인을 보이는 경우가 많다. 이 두 문장이 가장 중요할 듯 해요. 그냥 그렇습니다.