Reproduction

Players can modify their pawns' chances of pregnancy through many methods of Family Planning. Pawns can have kids from 16 years on, until their fertility drops to 0. During this time, you can modify a human's fertility through manual and automatic methods, whether you are hoping for kids or set on having none. You also have controls over the different ways your pawns can reproduce, whether by natural, surrogate, or artificial methods. A well-resourced player has a lot of control over how often their pawns get pregnant.

These are the factors going into a pawn's pregnancy chances, all of which the player has some control over: the pawn's relationship status, relationship habits, fertility (which includes age, genes, and contraceptives), sleeping habits, and the player-set strategy on having kids.

Romantic Relationships

Female pawns can begin a natural pregnancy after Lovin' a male partner (a lover, fiance, or husband). This makes a pawn's relationship status the primary factor in whether they will get pregnant soon. Players may help start romantic relationships in multiple direct, and indirect, ways. However, players don't have an easy control for breaking off a relationship.

Romance Controls

For any pawns over 16, the Social tab will have a "Romance..." button that allows the player to try instigating a romantic relationship between that pawn and another of the gender they're attracted to. This can be tried every 12 days, and can be done even when the pawns are already in relationships. You can only attempt to romance a target pawn that has a high-enough opinion of the current pawn and isn't closely related to them. Beyond this, their relationship and relative ages affect the Romance abilities chance of success.

Limitations

When you've selected the current pawn and attempt to Romance a target pawn, it won't be allowed if: the target pawn has a negative opinion of the current pawn (stating "low opinion"), the likelihood of success is too low (stating "zero chance"), or they are closely related (incestuous). Pawns that are under 16 or are of a gender the current pawn isn't attracted to will not even be shown on the dropdown list of potential Romance... targets.

Likelihood of success

With the current pawn selected, and the social tab open, you can see the chance of a Romance action's success by mousing over the target pawn's row in the social tab. It will tell you the probability of success and how it is calculated. The factors are: the target's opinion of the current pawn, the pawns' relative ages, certain genes and traits for the current pawn, and the target pawn's opinions of the people they already are in relationships with.

Beauty traits are major factors in the chance of success. An Ugly pawn (Beauty -1.0) has a x30% multiplier on success. A Pretty pawn (Beauty +1.0) has a x230% multiplier on success. Beauty here can be influenced by normal Beauty traits or Beauty-affecting genes.

Other genes can come into play as well. Someone with the Furskin gene has a x20% multiplier on romancing someone without it, and vice versa.

Note on relative ages The relative age factor doesn't just take into account the difference in age between colonists. It also factors in how old each colonist is. This effect is very large for young colonists. A 16 year-old's relative age factor with any colonist, of any age, will steadily increase from 0% to about 5% as they age from 16 to 17 biological years. This factor can still be affected by the other colonist's age as well: a late 16-year-old has a x4.4% multiplier on a relationship with a 46-year-old but a x4.1% multiplier with a 51-year-old. However, this is drastically outweighed by the young-age effect, because that same 16-year-old only has a ~1% multiplier on their romance chance with a younger 16-year-old.

Relative Age maximum by younger age

Once a colonist has reached the point where relative age isn't affected by their own youth, relative age is more affected by the difference in colonist ages.

Relative Age effect by age of male partner for a 22-year-old female

Indirect Relationship Controls

Starting and strengthening relationships

If you have the Royalty expansion, you can use abilities to increase a pawn's opinions of another, making it very likely that they will hook up soon if they run into each other enough and they keep trying to romance each other.

Breaking up relationships

You can try to decrease pawn's happiness and their opinions of each other to push them to break off their relationship. Another method is have one of them start an affair, when the other is in an ideology that doesn't condone free loving, to cause relationship harm.

Fertility

Fertility is the main pawn stat affecting pregnancy chances. Fertility changes with time and is affected by age and contraceptives, although genes can influence it too. Fertility affects more than just the chance of a natural pregnancy after pawns initiate Lovin': it affects all types of reproduction. For instance, once a woman becomes infertile, or sterile, you can no longer perform the operation "Extract ovum for IVF", to initiate a surrogate or artificial pregnancy.

Generally, women become infertile by age 50, and men lose fertility at a slower rate, only becoming infertile by age 90. Natural pregnancy explains in detail how age affects fertility for most humans. It remains to be seen how aging-related xenogerm genes affect this: perhaps some humans gain and lose fertility in unusual ways. Contraceptives also affect fertility, enabling you to bring a pawn's fertility to 0%, with no chance of pregnancy, through a number of temporary or permanent surgeries. Finally, fertility is also affected by several genes: it can be increased with the Fertile gene, or decreased with the Sterile gene.

Chances of Natural Pregnancy

The chance of a female pawn getting pregnant is affected by how often they do Lovin' with male pawns, and how fertile the pawns involved in the Lovin' are. The base chance for pregnancy after Lovin' can be seen by multiplying each pawn's fertility stats together. You can find this stat in the pawns' info panel, in the Stats>>Basics section. Beyond this, the player can set baby controls for each relationship, preferencing a higher or lower chance of pregnancy. Finally, the rate at which different couples do Lovin' varies drastically, and the player has some control over this.

Therefore, the total chance of pregnancy in one relationship is likely:

pregnancy chance per relationship = pawn A's fertility x pawn B's fertility x baby strategy x times Lovin'

A given pawn's total chance of pregnancy over time can be found by adding their chance of pregnancy across each relationship they are in.

The actual chance that a pair of pawns will do Lovin' each night varies by several factors. If they're in the same bed and sleep at the same time, their chance of Lovin' varies by age, as seen in this chart. Additionally, their chances are affected by their libidos, which can be altered from the default by the low libido and high libido genes. There have been reports that colonist mood and opinions of each other also influence the chance of doing Lovin'.

Baby Controls

The player has three options to adjust pregnancy rates from Lovin' in any relationship. By opening the social tab, to the right of a Lover, Fiancee, or Spouse, you can see a button that lets you change the couple's strategy for having kids.

By default, it is a hollow heart, with no preference for any pregnancy outcomes, and no affect on fertility.

If you change it to the sperm symbol, making the couple try for kids, their chance of pregnancy will be four times higher.

If you change it to the ban symbol, they will avoid pregnancy, with the chance getting four times smaller. If you're really worried about pregnancy and don't have the resources for contraceptives, you could place your now-unhappy couple in different beds so they won't do lovin' in the first place.

Contraceptives

There are many surgical methods for altering a pawn's fertility, affecting their chances of natural pregnancy. Some of these are revocable, allowing for pregnancy at a later time, but they have a slight chance of causing permanent sterility if a surgery is botched. You can access these medical operations after researching Fertility procedures. These surgeries can be applied to any pawn age 16 and up, and can be performed even if the pawn is already infertile.

IUD

You can stop a woman from becoming pregnant with the "Implant IUD" operation, which stops pregnancies in the first trimester. One can be placed indefinitely, with the operation requiring 1 medicine. You can later remove it through the "Remove IUD" medical operation, using a qualified doctor and 1 medicine. Women may embark with IUDs already implanted. If either of these operations is botched, the patient will become permanently sterile.

Vasectomy

Like an IUD, this is a semi-permanent way to make a pawn unable to reproduce. The health operation "Perform vasectomy", can be done on any adult male. It requires 1 medicine and is performed like a surgery. The vasectomy can be undone later through the "Reverse vasectomy" operation, also requiring 1 medicine. Both of these operations cause permanent sterility if botched.

Tubal Ligation

This permanently stops a female from being able to reproduce. "Perform tubal ligation" is a medical operation requiring 1 medicine.

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Biotech (DLC)

Families

Relationships (Reproduction • Children)
Life stages (Babies • Children • Adults)
Furniture (Crib • Baby sleeping spot • Growth vat • Toy box • Baby decoration • School desk • Blackboard)

Mechanoids

Laborers (Agrihand • Cleansweeper • Constructoid • Fabricor • Lifter • Paramedic • Tunneler)
Combatants (Centurion • Legionary • Militor • Scorcher • Tesseron)
Commanders (Apocriton • Diabolus • War queen • War urchin)

Mechanitors

Control (Mechlink • Band node • Mech boosters • Mech signallers • Control pack • Airwire headset)
Mechanoid creation (Basic subcore • Standard subcore • High subcore • Subcore encoder • Subcore softscanner • Subcore ripscanner • Mech gestator)
Maintenance (Mech recharger)

Genetics

Xenohumans (Dirtmoles • Genies • Highmates • Hussars • Impids • Neanderthals • Pigskins • Sanguophages • Wasters • Yttakin)
Genes Germline • Xenogene • Metabolic efficiency
Genetic Modification Genepack • Gene extractor • Gene bank • Gene assembler • Gene processor • Xenogerm • Archite capsules
Deathrest (Deathrest accelerator • Deathrest capacity serum • Deathrest casket • Glucosoid pump • Hemogen amplifier • Hemopump • Psychofluid pump)

Pollution

Nature (Toxalope • Toxipotato plant • Waste rat • Gray pine tree • Pebble cactus • Rat palm tree • Witchwood tree • Stasis cocoon)
Mitigation (Wastepacks • Atomizers • Pollution pumps • Polux trees)
Adaptation Face mask • Gas mask • Tox grenades • Tox pack • Tox shell • Toxic needle gun • Toxbomb launcher • Detoxifier kidney • Detoxifier lung
Nonchalance Toxifier generator