Pregnancy

The Sims 2 was, after all, designed to be a generation game. This is how you start a generation...

Sims can only get pregnant (without cheats or boolprop testingcheatsenabled) by using the action 'Try for Baby' when they are cuddling in a bed or hot tub, in a changing booth, or in a photo booth as well as in a car (Nightlife only).

Male sims can also get the joys of having children if they are abducted by aliens using the telescope.

Duration
All pregnancies last 3 days, with the exception of using cheats which can reduce the gestation period to a mere 2 hours in simtime.

Day one
On the first day the parent will suffer from morning sickness, in which they will run to the toilet periodically to throw up, with a thought bubble showing a pacifier and a question mark. As a sim is pregnant their motives will drop at an increased rate.

Day two
At some point in the day the parent will attract the player's attention and change appearance. Their abdomen will enlarge and they will begin to wear maternity clothing. Their needs still drop at an accelerated rate. The parent will be placed on maternity leave if they have a job. The carpool will not appear. There will be two new social interactions, 'Rub Belly' and 'Talk to Belly'.

From now until the baby is born, pregnant Sims can also expect to have cravings, in the form of more "Eat..." wants for specific foods.

Day three
The parent will get the attention of the player again and the abdomen will enlarge again. They can no longer drive, take a taxi, use the swing, hot tub or electro dance sphere from Nightlife. They will suffer from mood swings, in which the outcome of Social Interaction between the pregnant sim and another will change.

Birth
On the fourth day of the pregnancy the sim will attract the viewer once again and go into 'labour'. This is an autonomous action and all sims on the lot will be drawn to the sim to 'panic'. A screen will come up with the message 'there's a new family member on the way...' or 'there are two three or more new family members on the way...' at which time the genetics and gender of the new baby/s are being arranged. If the special camera is enabled a cinematic will commence showing the birth of the baby, or the sim will just turn around on the spot and... bam! A new family member. You will then be able to name the baby.

Twins
There is a slim chance that natural twins are produced. Most sims have about a 10% chance of having twins, although if the parent is a twin themself, the chances increase a bit. This is decided at the moment of conception, so, unlike gender and genetics, exiting and reloading the lot will not change the number of babies born. The cheat 'TWINSR2CUTE' does not work, and has never existed. However, released with Open for Business are two new methods of getting twins. The first is the cheat 'forcetwins' which, when typed in while the pregnant parent is selected, will ensure twin birth. The second is a pregnant sim eating cheesecake, which gives the player a HUGE chance of twins. You can also download third-party hacks from other websites, which give you the option to force your sim to have twins.

Triplets/Quadruplets
Without the use of a third-party hack, it is impossible to have triplets or quadruplets in The Sims 2.