Combined associations of prepregnancy body mass index and gestational weight gain with the outcome of pregnancy.

Background: Although both maternal prepregnancy body mass index (BMI) and gestational weight gain (GWG) may affect birth weight, their separate and joint associations with complications of pregnancy and delivery and with postpartum weight retention are unclear.

Objectives: We aimed to investigate the combined associations of prepregnancy BMI and GWG with pregnancy outcomes and to evaluate the trade-offs between mother and infant for different weight gains.

Design: Data for 60892 term pregnancies in the Danish National Birth Cohort were linked to birth and hospital discharge registers.

Physical exercise during pregnancy and the risk of preterm birth: a study within the Danish National Birth Cohort.

According to many national recommendations, women should be physically active during pregnancy, but empirical evidence to support this recommendation is sparse. The authors' aim in this study was to examine the relation between physical exercise during pregnancy and the risk of preterm birth. Self-reported data on physical exercise during pregnancy were collected prospectively for 87,232 singleton pregnancies included in the Danish National Birth Cohort between 1996 and 2002.

Maternal obesity and neonatal mortality according to subtypes of preterm birth.

Objective: To examine the association between prepregnancy body mass index (BMI) and neonatal mortality while accounting for the timing of delivery and subtypes of preterm birth.

Methods: The study population included 85,375 liveborn singletons of mothers in the Danish National Birth Cohort (1996-2002) who were interviewed during the second trimester. Information about pregnancy outcomes and neonatal deaths (n=230) was obtained from national registers.

Obesity, gestational weight gain and preterm birth: a study within the Danish National Birth Cohort.

The aim of the present study was to assess the impact of obesity and gestational weight gain on the risk of subtypes of preterm birth, because little is known about these associations. The study included 62 167 women within the Danish National Birth Cohort for whom self-reported information about prepregnancy body mass index (BMI) and gestational weight gain was available. Information about spontaneous preterm birth with or without preterm premature rupture of membranes (PPROM) and about induced preterm deliveries was obtained from national registers.

Stillbirth and slow metabolizers of caffeine: comparison by genotypes.

Background: Cytochrome P4501A2 (CYP1A2) and N-acetyltransferase 2 (NAT2) are key enzymes in the metabolism of caffeine. The polymorphism of these genes facilitates the detection of fast and slow metabolizers, and if caffeine is causally related to stillbirth, we expect slow metabolizers to have a higher risk of stillbirth at any given intake of caffeine. Gluthatione S-transferase alpha1 (GSTA1) may also be active in the metabolism of caffeine as it conjugates glutathione to aromatic amines.

Does low participation in cohort studies induce bias?

Background: Participation rates in large cohort studies have decreased during the last 2 decades. The consequences of this trend for relative risk estimation are unknown.

Methods: The impact of a low participation rate (30%) on the Danish National Birth Cohort was examined among 49,751 women from the source population, including 15,373 participants in the cohort study.

Coffee and fetal death: a cohort study with prospective data.

The authors conducted a cohort study within the Danish National Birth Cohort to determine whether coffee consumption during pregnancy is associated with late fetal death (spontaneous abortion and stillbirth). A total of 88,482 pregnant women recruited from March 1996 to November 2002 participated in a comprehensive interview on coffee consumption and potentially confounding factors in pregnancy. Information on pregnancy outcome was obtained from the National Hospital Discharge Register and medical records.

Prepregnancy obesity and fetal death: a study within the Danish National Birth Cohort.

Objective: To examine the association between high prepregnancy body mass index and fetal death, allowing for the effects of gestational age, weight gain, and maternal diseases in pregnancy.

Methods: Prepregnancy body mass index (BMI) and fetal death were examined in the Danish National Birth Cohort among 54,505 pregnant women who participated in a comprehensive interview during the second trimester. Pregnancy outcomes were obtained from registers and medical records.