Do primiparas aged 40 years or older carry an increased obstetric risk?
In our series, older primiparas were at increased risk for prematurity, preeclampsia, and perinatal mortality. The high rate of cesarean section in older primiparas is due mainly to a higher incidence of obstetric complications. These data suggest that the prenatal care of older primiparas in the third trimester should concentrate on the early detection of premature contractions and signs of preeclampsia.
These results differ in the model of gene-environment interaction that they support. The findings for any smoking initiation are consistent with the diathesis-stress model of gene-environment interaction; the findings for regular smoking initiation are consistent with the differential susceptibility model.