Maternal hand grip strength in pregnancy, newborn sex and birth weight

Hand grip strength (HGS) is a non-invasive measure of physical strength, overall health, and nutritional status. The aim of the study was to test if HGS and its changes in pregnancy are related with offspring sex and birth weight.

We conducted longitudinal study on 95 healthy pregnant women (mean age 29.57 ± 3.43). HGS was measured in each trimester. A woman's height and changes in weight in pregnancy were also measured. The information on a child's sex, birth weight and the pregnancy week at delivery were derived from hospital records. Fifty one women delivered a boy, and forty four women delivered a girl.

HGS decreased from the first to the third trimester of pregnancy (F(2,188) = 15.94, p < 0.001). Women with greater HGS in each trimester were more likely to give birth to a boy (p < 0.05), and the decrease in HGS in pregnancy was comparable in the two groups of mothers (F(2,186) = 1.39, p = 0.25). HGS in pregnancy was related with offspring birth weight when controlled for a child's sex and week at delivery (F(2,182) = 3.15, p = 0.04). Maternal height also important predictor of HGS in pregnancy, and the decrease in HGS was only observed in shorter women.

The results of this study indicate that HGS is a sensitive marker, differentiating the variation in physical condition in healthy, well-fed pregnant women in affluent population and pregnancy outcome (offspring sex and birth weight). Also, the result indicates that relatively taller women bear lower cost of pregnancy and are able to invest more in developing foetus.