Maternal BMI in Successive Pregnancies
Longitudinal Observational Study of BMI Changes in Successive Pregnancies
Researchers at the UCD Centre for Human Reproduction have published the results of a large longitudinal observational study examining changes in body mass index (BMI) of mothers between successive pregnancies. The study, published recently in the journal of the Obesity Society, found that one in five women who were overweight at the start of their first pregnancy were classified as obese by the time of their second pregnancy. Moreover, 88% of women who started in the obesity category at the start of their first pregnancy remained in this BMI category at the start of their second pregnancy.
The study was conducted in the Coombe Women & Infants University Hospital where routine, accurate and standardised measurement of both the height and weight of mothers was performed by trained midwives at the first prenatal visit since 1st January 2009. During the period 2009 to 2017, a total of 76,470 first prenatal appointments were recorded in the hospitals electronic health records. Of these, 9,724 women attended hospital for both their first and second deliveries of infants weighing ≥500 g and had their weight measured before 15 weeks of gestation. Women who had their weight first measured after 15 weeks of gestation in either pregnancy were excluded.
Among the cohort examined, the incidence of obesity increased from 11.6% in the first pregnancy to 16.0% in the second pregnancy. The mean inter-pregnancy interval was 32.5 months ± 15.7 months. The mean Body Mass Index change was +0.6 kg/m2 (interquartile range 2.2, P<0.001). Overall 10.3% developed overweight and 5.9% developed obesity by the second pregnancy. 20.6% of the first time mothers in the overweight category entered the obesity category in their second pregnancy.
Maternal obesity is known to present significant challenges in obstetrics and is associated with an increase in pregnancy complications, such as gestational diabetes, preeclampsia and venous thromboembolism. Maternal obesity also leads to increases in interventions during delivery through induction of labour and caesarean section. There are lifelong cardiometabolic consequences for both mother and her baby and increased societal healthcare costs.
The prevalence of obesity is increasing among high-income countries and although much research has gone into examining weight gain during pregnancy, the impact of weight gain between pregnancies and the associated risk factors is less well studied. Most studies of inter-pregnancy weight gain focus on pregnancy outcomes rather than the factors contributing to inter-pregnancy weight gain. Studies of maternal obesity have invariably been cross-sectional with self-reported maternal weight and height leading to less accurate BMI classification.
The study reported by Prof Michael Turner’s group was a longitudinal observational study with well characterised maternal BMI’s and examined both BMI and maternal weight changes in early pregnancy of nulliparas who returned to the Coombe Women & Infants University Hospital within a decade to deliver a second baby. The also examined characteristics and lifestyle factors associated with developing overweight or obesity in the inter-pregnancy period.
The prevalence of obesity increased in all groups of women studies in the second pregnancy. However, certain subgroups were identified as more likely to develop obesity. For example, women not in professional/managerial employment, women who were not exclusively breastfeeding at the time of hospital discharge, women taking antidepressants or anxiolytics, women who had postnatal depression after their first baby, and women who had an interval of 3 years or more between pregnancies had higher odds of developing obesity by the start of their second pregnancy.
Longitudinal Study of Maternal BMI in Successive Pregnancies
Ciara M. E. Reynolds, Brendan Egan, Eimer G. O’Malley, Léan McMahon, Sharon R. Sheehan,
and Michael J. Turner
Obesity 2020 Feb;28(2):460-467 [link]