Ellen Aagaard Nohr

: Objective. To examine the association between maternal obesity and infant mortality, while including information about mode of delivery and interpregnancy weight change. Design. Register‐based cohort study. Setting and population. A total of 1 199 183 singletons, including 3481 infant deaths, from the Swedish Birth Register 1992–2006. Methods. Maternal body mass index (BMI) was obtained from self‐reports in early pregnancy and categorized as underweight (2), normal‐weight (18.5–24.9 kg/m²), overweight (25–29.9 kg/m²), obese (30–34.9 kg/m²) and extremely obese (≥35 kg/m²). Cox regression was used to estimate hazard ratios (95% confidence intervals). Infants of normal‐weight women were the referent. Main outcome measures. Neonatal and infant mortality. Results. Infant mortality increased with increasing maternal fatness [adjusted hazard ratios 1.2 (1.1–1.3), 1.4 (1.2–1.6) and 2.1 (1.8–2.5) for overweight, obesity and extreme obesity, respectively]. When accounting for mode of delivery, neonatal mortality was increased in infants of obese and extremely obese mothers after spontaneous births [adjusted hazard ratios 1.8 (1.4–2.4) and 2.6 (1.8–4.0), respectively, after term births, and 1.4 (1.1–1.9) and 2.2 (1.5–3.3), respectively, after preterm births]. No excess risk was present for infants of obese mothers after induced term and preterm births (p‐values for interaction 1 BMI unit (1 kg/m²) seemed to involve a modest increase in neonatal mortality in the second infant, but only after spontaneous births [adjusted odds ratio 1.3 (0.9–1.7)]. Conclusions. Maternal obesity, especially at levels that may involve cardiometabolic morbidity, was associated with increased mortality in the offspring.

Exposure to infectious pathogens is a frequent occupational hazard for women who work with patients, children, animals or animal products. The purpose of the present study is to investigate if women working in occupations where exposure to infections agents is common have a high risk of infections and adverse pregnancy outcomes.

Little is known about reproductive health in severely obese women. In this study, we present associations between different levels of severe obesity and a wide range of health outcomes in the mother and child. From the Danish National Birth Cohort, we obtained self-reported information about prepregnant body mass index (BMI) for 2451 severely obese women and 2450 randomly selected women from the remaining cohort who served as a comparison group. Information about maternal and infant outcomes was also self-reported or came from registers. Logistic regression was used to estimate the association between different levels of severe obesity and reproductive outcomes. Subfecundity was more frequent in severely obese women, and during pregnancy, they had an excess risk of urinary tract infections, gestational diabetes, preeclampsia and other hypertensive disorders which increased with severity of obesity. They tended to have a higher risk of both pre- and post-term birth, and risk of cesarean and instrumental deliveries increased across obesity categories. After birth, severely obese women more often failed to initiate or sustain breastfeeding. Risk of weight retention 1.5 years after birth was similar to that of other women, but after adjustment for gestational weight gain, the risk was increased, especially in women in the lowest obesity category. In infants, increasing maternal obesity was associated with decreased risk of a low birth weight and increased risk of a high birth weight. Estimates for ponderal index showed the same pattern indicating an increasing risk of neonatal fatness with severity of obesity. Infant obesity measured one year after birth was also increased in children of severely obese mothers. Severe obesity is correlated with a substantial disease burden in reproductive health. Although the causal mechanisms remain elusive, these findings are useful for making predictions and planning health care at the individual level.

Dizygotic twinning rates have changed over time, which has been seen as a sign of a decline in fecundity. Since a woman's birthweight has been shown to be a marker of her fecundity, maternal birthweight may correlate with subsequent twinning rates. In the Danish National Birth Cohort (1996–2002), we examined if maternal birthweight, and whether she was born at term or preterm, correlated with her probability of multiple birth. For 20,719 live born infants, we had self-reported information about maternal birthweight, collected during the first wave of the 7-year follow-up, and information on multiple births from record linkage. The association between maternal birthweight and multiple births was investigated by use of logistic regression and presented as odds ratios (ORs) with 95% confidence intervals (CIs). Compared to women born at term with a birthweight of 3001–4000 g, women with a birthweight > 4500 g appeared to have higher chance of multiple birth while women with a birthweight of 4001–4500 had a lower chance, especially if the analysis was restricted to women with a BMI < 25 (Adjusted ORs 2.3 [1.0–5.4] and 0.4 [0.2–0.9] respectively). Odds ratios for dizygotic twinning were of the same magnitude. In women with a BMI ≥ 25, no obvious pattern was present. Our findings do not indicate that twinning is a fecundity indicator. Women with a birthweight that may indicate a pregnancy complicated with gestational diabetes had the highest rate of multiple birth. These findings are new and should be put to a critical test in other data sources.

Background: Recommendations for gestational weight gain (GWG) account for a woman’s prepregnancy body mass index (BMI), but other factors may be impo

An association between a woman’s own birthweight and her fecundity has been suggested, but no empirical data have been published on the association between maternal birthweight and waiting time to pregnancy (TTP). In the Danish National Birth Cohort (1996–2002), which is an ongoing study of 92 274 women and their pregnancies, information about TTP and prepregnancy BMI was collected during pregnancy. At the 7-year follow-up of the children, 21 786 mothers reported their own birthweight and whether they were born at term or preterm. The association between maternal birthweight and TTP is presented as adjusted odds ratios with 95% confidence intervals. Low maternal birthweight (≤2500 g for term and ≤1500 g for preterm birth) was associated with an increased risk of TTP of >1 year [term: 1.2 (1.0–1.5); preterm: 1.8 (1.1–3.1)]. The latter association was strongest in women with a BMI < 25 kg/m² [2.6 (1.4–4.7)]. High maternal birthweight (>4500 g for term and >3500 g for preterm) was also associated with an increased risk of TTP of >1 year [1.5 (1.0–2.0) and 1.3 (0.7–2.4), respectively], especially in women with a BMI ≥ 25 kg/m² [1.8 (1.1–3.1) and 2.5 (1.0–6.4), respectively]. High or low maternal birthweight was associated with TTP > 1 year. Longer waiting times in women with very low birthweight may reflect an effect of being born very preterm. Subfecundity may partly be programmed in foetal life by factors that cause or correlate with foetal growth.

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. Self-reported total GWG was categorized as low (Results: High and very high GWG added to the associations of high prepregnancy BMI with cesarean delivery and were strongly associated with high postpartum weight retention. Moreover, greater weight gains and high maternal BMI decreased the risk of growth restriction and increased the risk of the infant's being born large-for-gestational-age or with a low Apgar score. Generally, low GWG was advantageous for the mother, but it increased the risk of having a small baby, particularly for underweight women. Conclusions: Heavier women may benefit from avoiding high and very high GWG, which brings only a slight increase in the risk of growth restriction for the infant. High weight gain in underweight women does not appear to have deleterious consequences for them or their infants, but they may want to avoid low GWG to prevent having a small baby.