Low birth weight and prenatal care in Colombia: a cross-sectional study

The population was children born in Colombia from November 2006 to November 2010.

We included all children of women, 13 to 49 years of age, who answered the Colombian DHS 2010. We excluded children without reliable information on birth weight, and children born overseas.

The initial sample used in this study was all children born from women included in the DHS survey (13 to 49 years old) within the 36 months preceding data collection. This sample included 17,443 children, and it was reduced to 17,441 when children born overseas were excluded. The sample was further limited to those whose birth weight was either registered in the birth certificate, or the mother affirmed (during data collection) to accurately recall the birth weight and she provided a valid value. The final sample was 10,692 children.

The outcome variable was LBW, defined as the weight at birth of less than 2,500 grams (birth weight ≥ 2,500 g = 0; birth weight < 2,500 g = 1). Birth weight was the weight of the newborn in grams at the moment of birth regardless of gestational age or any other factor that might have an influence on it. Birth weight information was gathered either from birth certificates, or from information provided by a mother who affirmed recalling the birth weight accurately and provided a valid value.

The exposure variables were the characteristics of the prenatal care. Provider: divided in three dummy variables −1) No antenatal care, 2) Physician and 3) Other health professional-. Quality of prenatal care: this variable summarizes information on the interventions that the mother received during the prenatal care: education, physical examination –weight, height, uterine height, blood pressure-, immunization –tetanus-, tests -blood and urine-, and nutritional supplements –iron and folic acid-. A factor analysis indicated that the multiple interventions represented a single concept, hence, a new scale of quality of prenatal care was created (the scale had a score from 0 to 1, 0 being lowest quality and 1 being highest quality of prenatal care, alpha Cronbach 0.898. Women with no prenatal care had a score of 0). Number of prenatal care visits, First prenatal care (month in which the prenatal care was started. For women with no prenatal care it was coded as 9), and Health insurance coverage: mother’s health insurance covered prenatal care (0 = no; 1 = yes).

The control variables were divided in pregnancy characteristics, child characteristics, mother characteristics and context characteristics. The following pregnancy characteristics were considered: weeks of gestational age at delivery, preceding birth interval ≤ 1 year (0 = yes; 1 = no), substance abuse during pregnancy (score from 0 to 3 of the amount and type of substance abuse during pregnancy -tobacco, alcohol, marijuana, heroin and cocaine-), wanted child (regression score from a factor analysis of three variables: wanted the child, wanted the pregnancy and when did she want to become pregnant).

The child characteristics included in the analysis were sex (0 = male; 1 = female) and product of a multiple pregnancy (0 = no; 1 = yes).

The assessed mother characteristics were age (in years), education (in single years), employment (the mother is employed 0 = no; 1 = yes), marital status (divided in three dummy variables: 1) never married, 2) currently married and 3) previously married), height (in centimeters), body mass index (BMI) (divided in three dummy variables: 1) low –less than 18.5-, 2) regular –from 18.5 to 30-, and 3) high –above 30-), total children ever born, previously terminated pregnancy (0 = no; 1 = yes), history of sexual abuse (0 = no; 1 = yes), history of physical abuse (0 = no; 1 = yes), history of psychological abuse (0 = no; 1 = yes), and final say (regression score from a factor analysis of nine variables evaluating the women’s participation on household decisions).

Finally, the following context characteristics were considered: number of household members, wealth index (calculated by the DHS, with higher grades indicating greater wealth), urban residency (0 = no; 1 = yes), migration (living in the city of residence for less than a year), region (divided in 6 dummy variables: 1) Atlantic, 2) Oriental, 3) Central, 4) Pacific, 5) Bogota and 6) National Territories), household head (divided in three dummy variables: 1) woman, 2) partner and 3) other), and sanitation (score of clean water supply and healthy indoor environment).

Analysis of data was done using the IBM Statistical Package for the Social Sciences version 20 (IBM SPSS 20.0). A cut off P value of <0.05 was considered of statistical significance. First, descriptive statistics of all study variables were calculated -proportions for categorical variables, and mean, standard deviation, minimum and maximum for numerical variables-. Second, bivariate regressions of all study variables with LBW were obtained using chi square for categorical variables and independent sample t-test for numerical variables. Third, a stepwise binomial logistic regression of LBW on prenatal characteristics was conducted adjusting by child, mother and context characteristics. Bogota was excluded of the analysis for its collinearity with urban residence. Finally, a sensitivity analysis was conducted considering the missing values of low birthweight as low birthweight children and then considering the missing values as normal birthweight children.

The study was conducted using secondary sources. No identifying information was available to the researchers, nor informed consent was needed. It was approved by Universidad Del Rosario School of Medicine and Health Sciences, Ethics in Research Committee.

The final sample included 10,692 Colombian children. The descriptive statistics and bivariate analysis of the studied variables are shown in Table 1, for the total population, the normal birth weight population and the low birth weight population.

A LBW prevalence of 8.7 percent was found. In the total studied population, only a small percentage of women did not attend prenatal care (2.41%). Among normal birth weight (2.26 %) and LBW (3.68%) did not attend prenatal care. On the other hand, among those who received prenatal care the vast majority received prenatal care from physicians (92.95%). The average quality of prenatal care provided was very high (0.90 in a scale from 0 to 1; in which 1 is the highest quality SD = 0.17). Women attended on average 6.72 ± 2.81 prenatal visits, with a mean gestational age for the first prenatal visit of 2.5 months ±1.54, and most women had health insurance coverage (88.10%). Deliveries occurred on average at 38.82 weeks of pregnancy ± 1.99, a very small percentage of women had a previous pregnancy less than 1 year before (0.27%), and the substance abuse was uncommon. Multiple pregnancies occurred in less than 1 percent of the cases (0.78%), and 48.14 percent of the women delivered female newborns. The mean maternal age at time of delivery was 27.57 years ± 6.87, mothers had on average 9.17 years of education ±3.77, around half of the mothers were employed (48.23%), and most of them were currently married (73.73%). The average mothers’ height was 156 cm ± 58.83, meanwhile, percentages of low, normal and high BMI were 9.2, 73.93 and 22.49 percent, respectively. In terms of abuse, approximately half (48.13%) of the mothers reported being victims of psychological abuse, close to one in five of them had been victims of physical (17.87%) or sexual abuse (19.09%), and 22.49% had had an abortion.

A statistically significant difference on the absence of prenatal care between LBW infants (3.68%) and normal birth weight infants (2.26%), was found. On prenatal care characteristics: a physician provider was most commonly found for the group of normal birth weight (93.74%), as compared to the group of LBW, quality of prenatal care was higher for the group of normal birth weight (0.90 vs. 0.87), as well as number of antenatal care visits (6.12 vs. 6.79).Mothers with normal weight newborns were more likely to have health insurance coverage for antenatal care and delivery (88% vs. 85%). Time of first prenatal visit was not associated with LBW.

In terms of pregnancy characteristics: as expected, LBW newborns were product of pregnancies with lower gestational age (36 weeks vs. 39 weeks). Infants with LBW were more likely to be the outcome of pregnancies with shorter interval of time between pregnancies (0.60% vs. 0.23%), and these infants were less likely to be wanted, as compared with those infants who had a normal birth weight.

With regard to child characteristics: pregnancies resulting in LBW were more likely to have a female newborn (53.81% vs. 47.44%) and to be a multiple pregnancy (4.53% vs. 0.32%).

Mothers of LBW infants were more likely to be of a shorter height, have a low BMI and report a history of sexual abuse (not necessarily resulting on the studied child’s pregnancy).

Finally, regarding context characteristics, mothers living in the Central region (mostly rural area) were less likely to have children with LBW, while mothers living in Bogota (Colombia’s capital and most densely populated city) were more likely to have a LBW infant. Additionally, households headed by the woman’s partner were less likely to have babies with LBW.

The results of the binomial logistic regressions of LBW on prenatal care variables are presented in Table 2; model 1 unadjusted and model 2 adjusted for all the study variables. After adjusting for all the study variables; the absence of prenatal care (OR = 2.20), the quality (OR = 0.55) and quantity (OR = 0.93) of it, as well as the gestational age at first prenatal care visit (OR = 1.08), were associated with LBW.

Other associated factors were weeks of gestational age at delivery (OR = 0.63), product of a multiple pregnancy (OR = 9.72), sex (OR = 1.40), maternal education (OR = 0.96), maternal height (OR = 0.95), maternal low BMI (OR = 1.65), as compared to a regular BMI, history of sexual abuse (OR = 1.15) and other household head, as compared with woman’s partner head (OR = 1.33).