Association between second-to-fourth digit ratio (2D:4D) and blood pressure among pregnant women in Ekpoma, Nigeria: a cross-sectional study

The second to fourth digit ratio (2D:4D) is an anthropometric marker thought to reflect prenatal hormonal exposure and has been investigated in relation to cardiovascular outcomes. However, evidence regarding its relevance to blood pressure during pregnancy remains limited, particularly in African populations. This cross-sectional study recruited 100 pregnant women attending antenatal clinics in Ekpoma, Edo State, Nigeria. The lengths of the second and fourth digits on both hands were measured using a digital Vernier calliper, and 2D:4D ratios were calculated. Blood pressure was measured using a digital sphygmomanometer in accordance with standard guidelines. Descriptive statistics and Pearson correlation analyses were used to examine associations between digit ratios and systolic and diastolic blood pressure. Mean right-hand and left-hand 2D:4D ratios were 0.962 ± 0.039 and 0.974 ± 0.038, respectively. Mean systolic and diastolic blood pressures were 108.55 ± 12.25 mmHg and 65.42 ± 10.43 mmHg. No participant had systolic blood pressure ≥ 140 mmHg, and two participants (2%) had diastolic blood pressure ≥ 90 mmHg on the study visit; these measurements do not establish a diagnosis of hypertension. None of the four unadjusted correlations between 2D:4D and blood pressure was statistically significant (right-hand systolic: r = 0.002, p = 0.985; right-hand diastolic: r = 0.154, p = 0.125; left-hand systolic: r = 0.026, p = 0.800; left-hand diastolic: r = 0.171, p = 0.091). The 95% confidence intervals for the diastolic correlations extended from − 0.043 to 0.339 for the right hand and from − 0.026 to 0.355 for the left hand, so small-to-moderate positive associations cannot be excluded. This cross-sectional study did not detect a statistically significant association between 2D:4D and systolic or diastolic blood pressure in this predominantly low-risk cohort. The estimates were imprecise, particularly for diastolic blood pressure, and the data remain compatible with small-to-moderate positive associations. The findings should therefore not be interpreted as evidence that no association exists or as evidence that 2D:4D has predictive value. Larger longitudinal studies with greater blood pressure variability and adequate numbers of hypertensive outcomes are required.