Table 1.
Risk of hyperemesis and unadjusted odds ratio for hyperemesis with 95% confidence interval in women depending on occurrence of hyperemesis in their mothers, medical birth registry of Norway 1967-2006
| Hyperemesis in mother | No of pregnancies | No of daughters with hyperemesis | Risk of hyperemesis in daughters (%) | OR* (95% CI) |
|---|---|---|---|---|
| All mother-childbearing daughter units | ||||
| Yes | 3704 | 111 | 3.00 | 2.90 (2.35 to 3.57) |
| No | 540 383 | 5680 | 1.05 | Reference |
| Total | 544 087 | 5791 | 1.06 | — |
| Restricted to firstborn in both generations | ||||
| Yes | 934 | 30 | 3.21 | 3.20 (2.21 to 4.62) |
| No | 113 436 | 1162 | 1.02 | Reference |
| Total | 114 370 | 1192 | 1.04 | — |
*OR=odds ratio based on robust clustering accounting for dependencies within data. Of first generation mothers, 58% contribute to more than one family record. Adjustment for maternal age at childbirth and period of birth in both generations and maternal parity in first generation (when not restricted to first birth order) did not change estimates.