Gestational weight gain and blood pressure control in physiological pregnancy and pregnancy complicated by hypertension

Women in the third trimester of a singleton pregnancy were recruited for the study. This was a single-center prospective trial carried out between October 2014 and June 2017. Data regarding anthropometric and demographic factors – such as height, pregestational weight, gestational weight at the time of the examination, the history of hypertensive disease – were obtained by a questionnaire and compared, when available, with obstetric records to ensure accuracy. The analysed information regarding hypertension includes the time of diagnosis, highest values of systolic and diastolic blood pressure during pregnancy, treatment, and number of ambulatory blood pressure measurement tests. Chronic hypertension was defined as hypertension diagnosed before or during the first 20 weeks of pregnancy. Women with secondary hypertension were excluded from the study. Hypertension diagnosed after the twentieth week of pregnancy constituted gestational hypertension. As no data on postpartum resolution of blood pressure abnormalities were collected, this criterion was not a part of the used definition of gestational hypertension. There were no women with pre-existing hypertension with superimposed gestational hypertension with proteinuria in the studied group. This is a substudy of a project financed by the National Science Centre, Kraków, Poland (NCN 2013/11/N/NZ5/03388). The project was approved by the local Ethical Committee (opinion number 17/2013). Women were included in the study after providing a written informed consent.

Each women had an office blood pressure measurement obtained according to recommended guidelines with an Omron device certified for use during pregnancy [11]. Measurements were obtained on both arms.

We analysed the results for women in normal pregnancy and for women with hypertensive disorders of pregnancy separately. Afterwards a subanalysis of women with CH and GH was carried out. Body mass index (BMI) was calculated as weight in kilograms / height in meters squared. Descriptive data are presented as a mean or median depending on the distribution pattern. Differences between the groups regarding weight and BMI were calculated by Mann–Whitney U test. We decided to use the nonparametric test because of the size of the compared groups. Spearman correlation was calculated to examine the relationship between anthropometric parameters and blood pressure in each prespecified subgroup. SPSS Statistics 23 statistical software was used for the analysis. P value of less than 0.05 was considered as statistically significant.

The study group consisted of 61 women with HDP, 40 with GH, and 21 with CH, and 90 women in normal pregnancy. They were assessed during the third trimester. Between women in normal pregnancy and HDP there were no differences in age (30.5 ± 4.1 vs. 32 ± 4.7 years; p = 0.14) nor duration of pregnancy (32 ± 3.4 vs. 34 ± 3.8 weeks; p = 0.16). Subanalysis of the HDP group showed that women with GH had slightly higher gestational age compared with CH group at the time of assessment (Table 1). In the normal pregnancy group, 10 women (11%) were overweight and 5 (6%) were obese before pregnancy. In comparison 37.5% (15/40) of the GH and 38.1% (8/21) of the CH group were overweight before pregnancy. Obesity appeared in 20% (8/40) of GH group and 4.8% (1/21) of CH group. In total, prepregnancy weight and BMI were higher in the HDP group than in women with normal pregnancy (for weight 63.7 vs 72.1 kg; p < 0.001; for BMI 22.8 vs 26.2 kg/m2; p < 0.001). Interestingly, the change in weight (11.9 ± 4.6 vs. 12.2 ± 4.2 kg; p = 0.512) and in BMI (4.2 ± 1.8 vs. 4.4 ± 1.9 kg/m2; p = 0.352) during pregnancy were not different between the groups.

Both office systolic and diastolic blood pressure differed significantly among all three studied groups. Maximal blood pressure values were similar between the GH and CH group. Details are provided in Table 1.

In the normal pregnancy group, higher GWG was associated with higher office and maximal measurements of blood pressure (Table 2, Graphs 1 and 2).

Cumulative analysis of HDP group showed no correlation between blood pressure control parameters and GWG and BMI gain nor with prepregnancy weight and BMI values (Table 2).

Graph 1

Graph 2

Correlations between blood pressure and weight: gestational and chronic hypertension group subanalysis Correlation analysis between blood pressure measurements and anthropometric parameters was calculated in both types of HDP. Interestingly, although there were no correlations present in the GH group, a correlation between GWG and both maximal systolic and maximal diastolic blood pressure values measured during pregnancy were found in the CH group. A similar correlation with BMI change was noticed (for mSBP r = 0.561; p = 0.029 and for mDBP r = 0.681; p = 0.005). Details are shown in Table 2 and Graphs 3 and 4.

Graph 3

Graph 4

Presented results show that greater GWG up to the third trimester of pregnancy correlates with higher office and maximal blood pressure measurements. This finding is in line with evidence from the literature. In a study of 158 healthy pregnant women, GWG in the second and third tertiles resulted in lack of mid-trimester drop in systolic and diastolic blood pressure [13]. Macdonald-Wallis et al. describe results of 12,522 women from the Avon Longitudinal Study of Parents and Children [10]. They found that in normotensive pregnant women, with every 200g of gestational weight gain to 18 weeks of pregnancy there is about 30% of increase in risk of GH and preeclampsia, irrespective of prepregnancy weight. Lei et al. analysed the relation between trajectories of diastolic blood pressure values and GWG and found that women with highly increasing weight gain trajectory were at greater risk of being in the high-J shaped trajectory for diastolic pressure values [14]. This subgroup also had the highest values of systolic blood pressure values throughout the pregnancy. It seems also that prepregnancy weight gain leads to an increased risk of HDP [15].

Despite those findings there are no clinical recommendations regarding more screening, for example with ambulatory blood pressure monitoring, in women with excessive gestational weight gain for early diagnosis of HDP.

Excessive gestational weight gain, especially in early pregnancy, is recognised as a risk factor for GH, even independently of obesity prior to pregnancy [16]. Additionally, the greater GWG the higher this risk is across different races [17,18]. There are no data on the value of GWG and the control of GH once the diagnosis is made.

In our study there was a positive correlation between GWG and maximal systolic and diastolic blood pressure values during pregnancy, suggesting that it might be one of the parameters influencing blood pressure control. We did not observe correlation between GWG and measurement results obtained in the office, probably as a result of proper hypotensive treatment throughout further pregnancy.

No data on influence of GWG on blood pressure profile control in pregnant women with chronic hypertension were found. However, it is known that higher than recommended GWG increases maternal, obstetric and neonatal risks in this subgroup [19]. Excessive GWG in women without prepregnancy overweight or obesity aggravates risk of superimposed preeclampsia 3.5 times [20].

There are several limitations of our study. First, a small number of cases for particular subtypes of the HDP group was included. Second, we did not analyse the influence of GWG on pregnancy complications in the studied patients. Third, a 24-h ambulatory blood pressure monitoring was not performed as a part of the study protocol, which would have provided more averaged values of the measurements. And finally, the impact of treatment with antihypertensive medications was not evaluated.