Pregnancy hazards associated with low maternal body mass indices

Maternal underweight status and association with preterm contractions

OBJECTIVE

The purpose of the study is to investigate whether underweight pregnant women are more likely to be admitted for preterm contractions compared to normal or overweight women.

STUDY DESIGN

This is a retrospective, cohort study of patients who presented for preterm contractions from January 1, 2000, through January 1, 2008. Body mass index(BMI) categories include index rating of ·19 as underweight,20–25 as normal, and >25 as overweight, based on the National Institutes of Health standards. Preterm contractions were documented using an external tocodynamometer.Exclusion criteria included multiple gestations,gestational age under 24 weeks or over 37 weeks, neonatal anomalies, and premature rupture of membrane. Data was analyzed using SPSS 14.0. Statistical data was analyzed using a probability model. 2 testing compared the probability of admission as a function of weight groups as well as age and race variables.

RESULTS

Of the 840 patients identified with preterm contractions,7% were admitted while 93% were discharged.Of the total patients, 15% were underweight, 43% normal weight, and 42% overweight. Admission for preterm contractions was highest in underweight pregnant women(95%), followed by normal weight (5%). None were overweight.Both basic and augmented probability models showed that normal weight patients were less likely to be admitted for preterm contractions compared to underweight patients even after controlling for age and race.

CONCLUSION

These results suggest that underweight patients are more likely to be admitted for preterm contractions compared to normal weight patients. No overweight patients were admitted for preterm contractions.

Maternal underweight and the risk of spontaneous abortion

BACKGROUND

To evaluate the risk of spontaneous abortion in relation to maternal pre-pregnant underweight.

METHODS

The study was designed as a cohort study within the framework of the Danish National Birth Cohort (DNBC). The participants were a total of 23 821 women recruited consecutively to the DNBC from October 1, 1997 to March 31, 1999 and interviewed subsequently. The pregnant women were recruited in first half of pregnancy and interviewed about pre-pregnant body size, obstetric history, exposures in pregnancy, and socio-demographic factors. Pregnancies were followed-up regarding spontaneous abortion. Relative risk of spontaneous abortion was calculated as Hazard Ratios using Cox regression with delayed entry.

RESULTS

The outcome measure was spontaneous abortion. The hazard ratio for spontaneous abortion in women with a pre-pregnant body mass index (BMI) below 18.5 was 1.24 (95% confidence limits 0.95-1.63) compared to women with pre-pregnant BMI 18.5-24.9. Women with a BMI of 25 or more had a smaller increase in risk of spontaneous abortion. Adjustment for maternal age, parity, previous miscarriages, and lifestyle factors did not affect the estimates substantially, neither did exclusion of women with metabolic or eating disorders.

CONCLUSION

These results indicate that pre-pregnant underweight may affect the risk of spontaneous abortion negatively.