Doctor, my baby is small. How can I do?

Nancy lived with her younger sister for a long time until they found each own Mr. Right. They still kept tight after getting married. However, they both faced a difficulty at the same time — having no baby. Her sister chose to take the IVF treatment earlier due to the family stress. After two cycles, she finally delivered a cute baby girl. Nancy was encouraged by her sister, and met the fertility specialist with her husband.

She chose the IVF treatment directly as well, and got pregnant after one cycle. Although the bleeding frequently occurred during the first trimester, the gestation continued stably and no abnormality was reported, including her amniocentesis. Until six months of gestation, the obstetrician told her that the baby was smaller for the gestational age. The news made Nancy shocked and nervous.

So many mothers-to-be are like Nancy, and they are nervous about the body weight of fetuses.

There are several affecting factors to the fetal weight, such as congenital effects (different races or locations), nutrition intake, placental function, environmental risk or diseases. Usually, the fetus reported as small for gestational age (SGA) means that the fetal weight was under the 10th percentile of totality, or under the average gestational weight over two standard deviations. SGA roughly defines the fetuses with lower weights caused by any reasons, and 1/4 of SGA cases still can develop normally.

Intrauterine growth restriction (IUGR) specifically defines the fetuses with lower weights caused by some morbid reasons, including chromosomal abnormality, placental calcification or other diseases.

Two types of IUGR

1. Symmetrical IUGR:

It is mostly caused by the intrinsic reasons in fetus self. Both the weight and length are reduced. It could be due to aneuploidic syndromes (trisomy 13, trisomy 18) or intrauterine infection.

2. Asymmetrical IUGR:
It was mostly caused by the maternal reasons. The length and head circumference are in the normal range, but the weight is small. Asymmetrical IUGR often occurs in the last three months of gestation. It could be due to pre-eclampsia, diabetes, smoking or some medications.

Since fetal distress is more frequent in the SGA cases, the early diagnosis is very important. If SGA was observed, the doctors would classify the types and reevaluate the expected-date of child. By amniocentesis, the risk of chromosomal abnormality can be diagnosed. If the mother had diabetes or hypertension, both the medication and placental blood screening were necessary to ensure the blood/oxygen supply to fetus. Weekly non-stress test (NST) should be performed after three months of gestation to check the placental function continuously.

Generally, the fetal weight should be increased stably during gestation. Either over-weight or SGA should be consulted with the obstetricians to avoid any risk affecting fetal development.