Pregnancy

During puberty, gonads develop along similar lines to our world - singular eggs each month in ovaries (for female betas and omegas), steady sperm build up in testicles (for male alphas and betas). However, gonads may stay undifferentiated (able to become an ovary or a gonad) for much of childhood. In exceptional cases, differentiation may not happen until presentation in female alphas and male omegas.

During presentation, development changes. Ovaries (in all omegas) build up stores of eggs to release during quarterly heats. Sperm production in (all alpha) testicles starts to vary - slower in some periods, and then extremely heavy in others, allowing alphas to better match omega heat requirements. The make-up of semen during these heavy periods is different, as well. It contains hormones designed to jumpstart cellular growth. Eggs fertilized outside of heat will usually stay in the fallopian tubes/uterine horn until sex during heat allows them to soak up enough hormones to jumpstart development. (This means that a litter with multiple different sires is possible, though fertilized eggs may have decreased receptivity to seminal hormones from a different sire. Research is still ambiguous.)

For omegas, pregnancy outside of heat is unlikely, but possible. (This is not applicable for betas, who don't go into heat.) Fertilized eggs are usually lost if the next heat doesn't include sex. But singleton (one child, like our world, with the same possibilities for twins, etc) eggs may develop without seminal hormones. This usually begins immediately after conception, when the eggs continue to the uterus rather than staying put.

Male betas beget singletons. Female alphas only beget litters. Male alphas can do both, though litters are more likely with an omega partner. Female betas also only give birth to singletons (though they may have increased conception rates during the heavy part of their partner’s cycle), and while they CAN gestate only a single child from a litter, will usually have lower conception rates with female alpha partners. Male omegas can concieve singletons, but their uterus isn't designed for them and singleton pregnancies are often lethal.