When Louise Brown was born on 25 July 1978, she kicked off an era. The first "test tube baby" is a mother herself now, and she’s been joined by millions of others born with the (47) of in vitro fertilization (体外受精), or IVF. Now specialists wonder whether people who were conceived by IVF are likely to be (48) .
"By and large, the kids are just fine. It’s not like the kids having (49) arms or heads," says Carmen Sapienza, a scientist at Temple University. But none is older than their early 30s, and the vast (50) are under the age of 20, so they haven’t had time for long-term health problems to show up.
One source of worry is that so many IVF babies have low birth weight. Children-conceived through IVF are more likely to (51) less than 2.5 kilograms than are babies conceived (52) . That could spell trouble ahead, because low-birth-weight babies often have long-term health problems. They’re more likely to be obese, to have diabetes (糖尿病) or other problems.
With that in mind, Sapienza and colleagues have looked at genes that are likely to play a role in such health problems. They found that certain DNA-patterns, which affect how genes are (53) , are different between IVF and non-IVF children. There’s no way to tell if that’s because of the (54) used to produce the IVF babies or whether the difference has something to do with the underlying infertility problem the parents had. It’s also (55) whether these gene-expression differences will translate into health differences. But it does suggest that children conceived by IVF are (56) on some level.

• A) weigh
• B) technology
• C) help
• D) unsure
• E) unclear
• F) naturally
• G) expressed
• H) procedure
• I) unique
• J) healthy
  K) explained L) extra M) majority N) minority O) completely