Annual body mass index gain and risk of hypertensive disorders of pregnancy in a subsequent pregnancy

Abstract

Weight gain during interpregnancy period is related to hypertensive disorders of pregnancy (HDP). However, in interpregnancy care/counseling, the unpredictability of the timing of the next conception and the difficulties in preventing age-related body weight gain must be considered while setting weight management goals. Therefore, we suggest considering the annual change in the body mass index (BMI). This study aimed to clarify the association between annual BMI changes during the interpregnancy period and HDP risk in subsequent pregnancies. A multicenter retrospective study of data from 2009 to 2019 examined the adjusted odds ratio (aOR) of HDP in subsequent pregnancies. The aORs in several annual BMI change categories were also calculated in the subgroups classified by HDP occurrence in the index pregnancy. This study included 1,746 pregnant women. A history of HDP (aOR, 16.76; 95% confidence interval [CI], 9.62 - 29.22), and annual BMI gain (aOR, 2.30; 95% CI, 1.76 - 3.01) were independent risk factors for HDP in subsequent pregnancies. An annual BMI increase of ≥ 1.0 kg/m²/year was related to HDP development in subsequent pregnancies for women without a history of HDP. This study provides data as a basis for interpregnancy care/counseling, but further research is necessary to validate our findings and confirm this relationship.

Figure 1

Flow chart of the study subjects. Clinical data were obtained from 2011 women who delivered at two tertiary centers or 12 primary maternity care units for whom two serial pregnancy records were available were obtained. A total of 1746 women were eligible for this study after excluding 196 and 69 women based on the index and subsequent pregnancy data, respectively.

Figure 2

Overview of the definitions of terms. We defined interpregnancy BMI change (ΔBMI) as a change in pre-pregnant BMI from the index pregnancy to the subsequent pregnancy. The interpregnancy interval was defined as the interval from the expected date of delivery of the index pregnancy to that of the subsequent pregnancy, which is equivalent to the interval between the two conceptions. The annual BMI change was calculated as the ΔBMI/pregnancy interval. Gestational weight gain was defined as the change between pre-pregnant body weight and that before delivery. BMI, body mass index.

Figure 3

Adjusted odds ratios of classified annual BMI change for HDP in the subsequent pregnancy. The multivariable models were adjusted for maternal age in the index pregnancy, pre-pregnant BMI in the index pregnancy, classified annual BMI change, and interpregnancy interval. The values on the left side of the graph are expressed as log₂OR. The right side of the graph shows the incidence of HDP in subsequent pregnancies according to the degree of annual BMI change. The number of HDP events in the subsequent pregnancy/total number is also shown according to the degree of annual BMI change. BMI, body mass index; CI, confidence interval; HDP, hypertensive disorders of pregnancy *Statistically significant.

Figure 4

Adjusted odds ratios for HDP in the subsequent pregnancy among those without the history of HDP in the index pregnancy. The multivariable models were adjusted for maternal age in the index pregnancy, pregnancy interval, and classified annual BMI change. Values on the left side of the graph are expressed as log₂OR. The right side of the graph shows the incidence of HDP in the subsequent pregnancy according to the degree of annual BMI change. The number of HDP in the subsequent pregnancy/total number is also shown according to the degree of annual BMI change. BMI, body mass index; CI, confidence interval; HDP, hypertensive disorders in pregnancy.