Leisure time physical exercise during pregnancy and the risk of miscarriage: a study within the Danish National Birth Cohort

Objective  To examine the association between leisure time physical exercise during pregnancy and the risk of miscarriage.
Design  Prospective study with elements of retrospective data collection.
Setting  Denmark 1996–2002.
Population  A total of 92 671 pregnant women enrolled in the Danish National Birth Cohort and interviewed subsequently.
Methods  Data on exercise during pregnancy and potential confounders were obtained through computer-assisted telephone interviews either during pregnancy or after an early miscarriage. Outcome of pregnancy was identified by register linkage. Using Cox regression analysis, we estimated the hazard ratio (HR) of miscarriage according to weekly amount of exercise and the type of exercise. The HR was estimated for <11, 11–14, 15–18, and 19–22 weeks of gestation, respectively.
Main outcome measures  Miscarriage, defined as fetal loss before 22 completed weeks of gestation.
Results  A stepwise increasing relation was found between amount of exercise and risk of miscarriage, where risk of miscarriage increased by amount of exercise up to HR = 3.7 (95% CI 2.9–4.7) for women who exercised more than 7 hours per week compared with nonexercisers. Particularly 'high-impact exercise' was associated with an increased risk of miscarriage. No association was seen between exercise and risk of miscarriage after 18 weeks of gestation.
Conclusions  This study suggests that exercise early in pregnancy is associated with an increased risk of miscarriage. The results should, however, be interpreted cautiously as potential bias arising from retrospective data collection may explain part of the association.     

Changes in NK cell activity during the estrous cycle and pregnancy in mice

Changes in NK cell activity during the estrous cycle and pregnancy in mice were studied by a 4 h 51Cr-release assay using YAC-1 cells as a target. NK activity both in the spleen and peripheral blood mononuclear cells showed a single fluctuation with a peak at met-estrous-2 during the estrous cycle. Splenic NK activity was suppressed in the early to mid-stages of pregnancy but increased sharply in the late stage. The activity declined thereafter, reaching the estrous level post-partum. NK activity in the peripheral blood showed a decrease throughout the entire pregnancy, but increased on Day 1 post-partum, returning to the estrous level thereafter. To elucidate the mechanisms involved in these variations of NK activity, NK-enriched and non-adherent cells were prepared from the spleens of mice at estrous and met-estrous-2 and those at early and late stages of pregnancy and then examined for NK activity. The results showed that there was no difference in the cytotoxic activity among these purified NK cells. Adherent cells purified from the spleens of mice in the early stage of pregnancy when co-cultured with the non-adherent NK cell fractions suppressed the NK cytotoxicity. These results strongly suggest the possibility that phagocytic and/or adherent cells may be involved in the regulation of splenic NK activity during the estrous cycle and pregnancy.     

Measuring physical activity in pregnancy: a comparison of accelerometry and self-completion questionnaires in overweight and obese women

Objectives

Increased physical activity in pregnancy may reduce the risk of gestational diabetes and pre-eclampsia, which occur more commonly in overweight and obese women. There is limited assessment of physical activity questionnaires in pregnancy. This study compares self-reported physical activity using two questionnaire methods with objectively recorded physical activity using accelerometry in overweight and obese pregnant women.

Study design

59 women with booking BMI ≥ 25 kg/m² completed the Recent Physical Activity Questionnaire (RPAQ) and Australian Women's Activity Survey (AWAS) or recorded at least 3 days of accelerometry at median 12 weeks’ gestation. Accelerometer thresholds of 100 counts/min and 1952 counts/min were used to define light and moderate or vigorous physical activity (MVPA) respectively.

Results

48% of women were in their first pregnancy and 41% were obese. Median daily self-reported MVPA was significantly higher for both AWAS (127 min, p < 0.001) and RPAQ (81 min, p < 0.001) than that recorded by accelerometer (35 min). There was low or moderate correlation between questionnaire and accelerometer estimates of total active time (AWAS ρ = 0.36, p = 0.008; RPAQ ρ = 0.53, p < 0.001) but no significant correlation between estimates of time spent in MVPA.

Conclusions

These self-report questionnaires over-estimated MVPA and showed poor ability to discriminate women on the basis of MVPA. Accelerometry measurement was feasible and acceptable. Objective methods should be used where possible in studies measuring physical activity in pregnancy. Questionnaires remain valuable to define types of activity.