Maternal age was not included in any of the models because data available from clinics 2 and 3 were incomplete, and parity is closely related to age in this population (40).
Then we studied the effect of parity, incomplete pregnancies and breast-feeding for homogeneous regions previously described in our data [ 30] where a central low BC risk region in BRCA1 and BRCA2 was confirmed [ 27, 28, 31- 34], and a new high-risk region in BRCA2 was described [ 30].
The protection from breast cancer afforded by parity is incomplete.
The percent incomplete tests is in parity with conventional neuropsychological testing in INPH, where in one study, the Stroop test was completed by 70% of the patients [ 43].
Exclusion criteria were incomplete information on year, parity, plurality, birth weight, or mode of delivery, because missing information in these variables would prevent classification into the Robson groups.
Estimated risks of BC associated with parity and incomplete pregnancy by homogeneous region in BRCA1 are shown in Table 4. Parity seems to be associated with a significantly decreased risk of BC only among women with a mutation in LR1 (≥1 versus 0 FTP: HR = 0.27, 95% CI = 0.13 to 0.55) (Pinteraction <10-3).
Although parity is an incomplete measure of contact with older children within the household, it was the only measure available to us.
Parity, breast-feeding, incomplete pregnancies, menopausal status and oral contraceptive use changed over time, so it was analyzed as a time-dependent covariate and cumulative over life time.
Women with incomplete covariate data (i.e., parity (parous/nulliparous, number of children) and OC use (never/ever)) were excluded, leaving 375 cases and 2,331 subcohort members for analysis.
Specific obstetric data including numbers of previous pregnancies (gravida), previous viable births (parity) and gestations were incomplete in many cases (Table 2).
