Examining suspected dietary predictors of gestational hypertension in Iceland

Abstract

The aim of this study was to investigate the association between few specific dietary factors such as fish, fish liver oil, coffee and tea during pregnancy and hypertensive disorders in pregnancy. The research questions that will be addressed is whether high consumption of fish or fish liver oil during pregnancy among Icelandic women can increase the risk of gestational hypertension; and if whether coffee or tea intake during pregnancy can reduce the risk of developing preeclampsia.A cohort of 491 pregnant Icelandic women who gave birth at landspitali National University Hospital, Reykjavik, Iceland in 1998. Women with pre-pregnant normal weight (BMI 19.5-25.5 kg/m2) were randomly selected from maternal records. The women were healthy before pregnancy, and had no history of hypertension, diabetes, cardiovascular disease, or thyroid problems. They were aged between 20-40 years old, and delivered singleton infants at 38.-43.week of gestation. Information on dietary intake was collected from maternal records by a food frequency questionnaire (FFQ). Maternity records gave information on maternal age, height, marital status, pre-pregnant weight, gestational weight gain, smoking and parity. Information on gestational hypertension and preeclampsia was diagnosed at the Department of Obstetrics and Gynecology, Landspitali National University Hospital. We used gestational hypertension is defined as systolic blood pressure (SBP) ≥ 140 mmHg and/or diastolic blood pressure (DBP) ≥ 90 mmHg on two or more occasions after 20 weeks of gestation, but without proteinuria as a primary outcome measure. Systolic and diastolic, isolated systolic, and isolated diastolic hypertension were used as secondary outcome measures. Preeclampsia was diagnosed as gestational hypertension and proteinuria of ≥ 0.3 g/24h or at least 1+ on a dipstick.In the first study we observed that the prevalence of gestational hypertension and preeclampsia was 102 (21%) and 15 (3%), respectively. Fish consumption was not associated with hypertensive disorders in pregnancy. Intake of fish liver oil was, however, positively associated with pregnancy hypertension defined as systolic blood pressure (SBP) ≥ 140 mmHg and diastolic blood pressure (DBP) ≥ 90 mmHg. Using this definition women consuming one table spoon (≈ 9g) a day or more had an adjusted odds ratio of 6.3 (95% CI 2.2; 17.9) of having pregnancy hypertension compared to those with no intake. This association appeared to be driven by a relative shift from isolated diastolic hypertension to combined systolic and diastolic hypertension as fish liver oil was not associated with hypertension defined as (SBP) ≥ 140 and/or (DBP) ≥ 90.Our results suggest that high (≈ 9 g/day) intake of fish liver oil may affect the severity of gestational hypertension. These findings are in line with previous reports about other cohort from Iceland were high consumption of fish liver oil has been associated with hypertensive disorders in pregnancy.In the second study we found that coffee was not associated with gestational hypertension defined as (SBP) ≥ 140 and/or (DBP) ≥ 90. Compared with non-coffee consumption, coffee consumption of the women during pregnancy was associated with a reduced risk of preeclampsia (crude odds ratio (OR) 0.16, 95% CI 0.04; 0.73). This association was also found after adjustment for covariates with adjusted OR of 0.15 (95% CI 0.03; 0.82). Tea intake, however, was not associated with hypertensive disorders in pregnancy.Our results suggest that high intake of fish liver oil in pregnancy may be associated with an increased risk of gestational hypertension and moderate consumption of fish liver oil, thus, should be recommended. We can not rule out that substances other than n-3 LCPUFA in fish liver oil as vitamin A (retinol) and PCBs may influence gestational hypertension. Coffee consumption during pregnancy may lower risk of preeclampsia. However, reverse causality may also contribute to these findings. More research, however, is needed to confirm these findings and to investigate further elucidation of underlying pathophysiological mechanisms may indicate a role for coffee to prevent risk factors on hypertensive disorders in pregnancy.Key words: Fish, fish liver oil, coffee, tea, gestational hypertension, preeclampsia and hypertensive disorders in pregnancy.