[Study on the third trimester hemoglobin concentrations and the risk of low birth weight and preterm delivery].
OBJECTIVE
To investigate the association between third trimester hemoglobin (Hb) concentrations and the risk of low birth weight and preterm delivery in a Chinese population.


METHODS
Subjects were women who delivered in four cities/counties in Jiangsu and Zhejiang provinces, China, during the period of 1995 - 2000. Incidence of low birth weight and preterm delivery was calculated and compared among groups of women with different levels of Hb during the third trimester. Multiple logistic regression was used to address relationships between Hb levels and the risk of preterm delivery and low birth weight while controlling for potential confounding factors.


RESULTS
The overall prevalence of anemia during third trimester of pregnancy was 48.2% , mainly consisting of mild and moderate anemia. Mild and moderate anemia did not increase the risk of preterm delivery and low birth weight statistically. The lowest incidence of preterm delivery and low birth weight was found among pregnant women with Hb levels at 90-99 g/L. The risk for preterm delivery and low birth weight increased with either increasing or decreasing hemoglobin concentrations. However,there was no remarkable elevation of the risk when Hb was in the range of 70-119 g/L. Women with severe anemia (Hb< 70 g/L) had 80% higher risk (95% CI:1.0-3.3) of preterm delivery and a 4.0-fold higher risk (95 % CI :2. 1-7.5) of low birth weight compared with women with an Hb value of 90-99 g/L. In addition, women with a high Hb concentration (Hb> 130 g/L) had 20% higher risk (95 % CI: 1..0-1.4) of preterm delivery and 50 % higher risk (95 % CI: 1.2-1.9) of low birth weight.


CONCLUSIONS
A U-shape relationship was found between Hb concentration and the risk of preterm delivery and low birth weight. Severe anemia and high hemoglobin concentration were both associated with increased risk of preterm deliveries and low birth weight.
Wang
Juan
J
Institute of Reproductive and Child Health, Peking University Health Science Center, Beijing 100083, China.
Ren
Ai-guo
AG
Ye
Rong-wei
RW
Zheng
Jun-chi
JC
Li
Song
S
Liu
Jian-meng
JM
Yang
Rui-lan
RL
Zhang
Fei-ran
FR
Zhang
Tan
T
Zhang
Jing-bo
JB
Li
Zhu
Z
D000328:Adult; D036861:Delivery, Obstetric; D005260:Female; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D007230:Infant, Low Birth Weight; D007231:Infant, Newborn; D007234:Infant, Premature; D011247:Pregnancy; D011263:Pregnancy Trimester, Third; D047928:Premature Birth / Q000097:blood* / Q000453:epidemiology*; D012307:Risk Factors; D055815:Young Adult
D006454:Hemoglobins