Background and Aim: Unwanted pregnancy is a widespread problem globally and in Iran, which can lead to low birth weight (LBW)-one of the most important causes of mortality in newborns. This study was conducted to assess the risk factors among women with unwanted pregnancies leading to delivery of LBW infants. Other LBW risk factors were also studied.

Methods and Materials: This was a prospective cohort study performed during March 2004 to April 2005 in the health centers of Shemiran, north of Tehran, Iran. A sample of 180 mothers, 15-49 years old, with an unwanted pregnancy (case group) and 430 mothers, in the same age group, with a wanted pregnancy (control group) were compared. To determine the effect of unwanted pregnancy three major type of variables (background, maternal, and neonatal variables) were selected, and the mothers were followed up for 11-12 months (from the first referral for prenatal care to about 2 months after delivery). Statistical univariate analyses were performed using the t- and χ2 tests. Also, multiple logistic regression was employed to identify the risk factors associated with LBW. SPSS 11.5 for windows was used for data analysis.

Results: The unwanted pregnancy prevalence was 11.7%. The mean of Apgar score was 8.6 in the case group and 8.9 in the control group, the difference being statistically significant (p<0.001).Mean birth `1234t5weight of neonate in the case group was about 2.984kg vs. 3.14kg in the control group, and the difference was statistically significant (p<0.001) . Univariate analysis showed that LBW was related to unwanted pregnancy (p<0.001), gestational age (p<0.001), mother's age (p<0.001), mother's marriage age (p<0.001), birth order (p<0.001), number of past pregnancies (p<0.001), family size (p<0.001), number of abortions (p<0.001), attempt to abort (p<0.001), high blood pressure (p<0.001), and diabetes (p<0.001). Finally, multivariable analysis revealed that LBW was only associated with unwanted pregnancy, high blood pressure, and diabetes in mothers, with adjusted odd ratios of 2.22, 2.81 and 3.55, respectively (p<0.05).

Conclusion: Prevention of unwanted pregnancies, increased gestational age, and appropriate management of mothers' chronic diseases can reduce the risk of LBW.