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Objective. To study the impact of pregnancy on estimated peak oxygen uptake ((V) over dotO(2) (peak, est.)), physical activity and perceived health. Design. Prospective cohort study. Setting. Maternal health centers. Population. A cohort of pregnant women. Methods. Cycle ergometer test and questionnaires in early pregnancy and 5 months postpartum. Main outcome measures. (V) over dotO(2) (peak, est.), physical activity and perceived health. Results. Regular physical activity was reported by a successively lower proportion of women as pregnancy advanced but the proportion was regained postpartum. Despite this the difference between average absolute (V) over dotO(2) (peak, est.) in early pregnancy and postpartum of 2.44 and 2.42 l/minute, respectively, was not significant. The adjusted absolute (V) over dotO(2) (peak, est.) in early pregnancy successively increased with age to a maximum at 35 years, after which it decreased and among women of the same age the time between 8 and 12 weeks lowered the (V) over dotO(2) (peak, est.) by 0.130 l/minute. With the Short Form 36 (SF-36) questionnaire in early pregnancy the women scored their mean mental health to 72.0 and mean physical health to 79.7. At the postpartum appointment these scores were higher (p < 0.0001). Absolute and relative (V) over dotO(2) (peak, est.) in early pregnancy were positively correlated to the variation of SF-36' s mean physical health in early pregnancy (p < 0.0001) and postpartum (p < 0.0001). Conclusions. Pregnancy had a moderate influence on physical fitness and perceived health half a year postpartum despite less regular physical activity during pregnancy. (V) over dotO(2) (peak, est.) in early pregnancy was positively correlated to perceived physical health.

Background: Low back pain with onset during pregnancy is common and approximately one out of three women have disabling pain. The pathogenesis of the pain condition is uncertain and there is no information on the role of physical fitness. Whether poorer physical conditioning is a cause or effect of back pain is also disputed and information from prospective studies needed. Methods: A cohort of pregnant women, recruited from maternal health care centers in central Sweden, were examined regarding estimated peak oxygen uptake by cycle ergometer test in early pregnancy, reported physical activity prior to pregnancy, basic characteristics, back pain during pregnancy and back pain postpartum. Results: Back pain during the current pregnancy was reported by nearly 80% of the women. At the postpartum appointment this prevalence was 40%. No association was displayed between estimated peak oxygen uptake and incidence of back pain during and after pregnancy, adjusted for physical activity, back pain before present pregnancy, previous deliveries, age and weight. A significant inverse association was found between estimated peak oxygen uptake and back pain intensity during pregnancy and a direct association post partum, in a fully adjusted multiple linear regression analysis. Conclusions: Estimated peak oxygen uptake and reported physical activity in early pregnancy displayed no influence on the onset of subsequent back pain during or after pregnancy, where the time sequence support the hypothesis that poorer physical deconditioning is not a cause but a consequence of the back pain condition. The mechanism for the attenuating effect of increased oxygen uptake on back pain intensity is uncertain.

Study question: Are oxygen uptake and the pleiotropic hormone relaxin associated with the mechanism of blood pressure during pregnancy?

Summary answer: Diastolic blood pressure, but not systolic, displayed a significant reduction with increased oxygen uptake and increased serum relaxin levels.

What is known already: Data showing an inverse association between serum relaxin concentrations and either blood pressure during pregnancy or hypertension has been suggested. An association of oxygen uptake with blood pressure during pregnancy has not been previously reported.

Study design, size, duration: A prospective cohort study of 520 pregnant women in early pregnancy from March 2001 to June 2003.

Participants/materials, setting, methods: Baseline data collection in early pregnancy included submaximal cycle ergometer test and blood sampling. The participants were followed repeatedly throughout pregnancy with blood pressure measurements at Maternal Health Centers.

Main results and the role of chance: Oxygen uptake, serum relaxin concentrations, number of previous deliveries, and cigarette smoking were demonstrated to be negatively associated with, and height positively associated with (all independently) average diastolic blood pressure (p<0.0001) by multiple regression analysis. Similarly, number of previous deliveries, and cigarette smoking were negatively associated with, and height positively associated with, (all independently) systolic blood pressure (p=<0.0001)

Limitations, reasons for caution: The blood pressure was measured to the nearest 5 mmHg instead of the recommended 2 mmHg, which probably reduced the sensitivity to show only the strongest association to blood pressure.

Wider implications of the findings: The results give clinical implication for non-pharmacological approach of lowering of blood pressure during pregnancy in a public health perspective.

Background: Women are recommended to perform regular exercise during pregnancy but the impact of physical fitness on duration of gestation including miscarriage is inconsistent. In addition, an increased risk of miscarriage in early pregnancy among women with higher levels of physical activities has been noted. Previous studies have mostly used an epidemiologic method. Larger studies using careful measurement of physical fitness are needed. Besides physical fitness, elevated maternal circulating levels of the hormone relaxin have been associated with decreased duration of gestation.

Methods: A prospective cohort including 20 women with miscarriage and 460 women with spontaneous start of labour, recruited from maternal health care centres in central Sweden, were examined regarding estimated absolute peak oxygen uptake (V̇O_{2 peak, est..}) by cycle ergometer test, and maternal circulating relaxin levels in early pregnancy.

Results: Women with miscarriage displayed the highest level of absolute V̇O_{2 peak, est.} (2.61 l/min) and the lowest serum relaxin levels (640 ng/l). Among women with spontaneous start of labour, the mean absolute V̇O_{2 peak, est.} increased successively from the lowest level (2.31 l/min) among those with preterm birth (n=28), to 2.49 l/min among women with post term birth (n=31). An opposite trend was shown regarding serum relaxin levels from women with miscarriage to those with post term birth. Serum relaxin concentrations, but not absolute V̇O_{2 peak, est.} was significantly and independently associated with duration of gestation in women with miscarriages, and absolute V̇O_{2 peak, est.}, age and multiple pregnancy were independently associated with duration of gestation in women with spontaneous start of labour.

Conclusions: Physical fitness appears to be a protective factor of established pregnancies and not significantly involved in the risk of early miscarriage. Additional studies are needed to more clearly define the role of relaxin in miscarriage.