You can also use the Prostitute Pro implant to avoid pregnancies (and vaginal cumflation). Interestingly, because Prostitute Pro doesn't technically render Steele infertile, it doesn't prevent Heat.
More specifically:
1.
Motherhusks can increase base Incubation bonus to 700%, but it will also cause 40 Taint (total) and they're a Rare Drop.
2.
Laquine Ears can increase bae Incubation bonus to 1000%, but it's a random effect, so expect to use a lot of them or save-scum hard.
3.
Breed Hungry is +100% that stacks with the previous. It also reduces the (Pregnancy) Bulky Belly penalty.
4. Synth Womb is +800%, also stacking.
5. Incubator would be another 100%, but you're past Character Creation, so it's not an option, unless you already have it. Or you console it in.
Effective Incubation bonus is the average of Maternal and Paternal bonus (always 100%), so your effective bonus is 1/2 of your displayed number.
The bonus for an active pregnancy is fixed at the time of conception.