You can bring it up with your clinic, but asking for twins isn’t something you order. You can ask to transfer two embryos instead of one, but that doesn’t reliably produce twins — both may implant, one may, or neither. And it’s something clinics generally steer away from, especially for good-prognosis patients, because twins raise the risk of complications for both babies and parent.
Transferring two embryos
Twins from IVF almost always come from a double embryo transfer, or DET. The recommended default under ASRM and SART guidance is elective single embryo transfer (eSET). If embryos have been genetically tested and come back normal, that’s one embryo regardless of patient age. Without testing, the guidance varies with age (limits below are for blastocyst-stage embryos; day-3 cleavage-stage limits run higher):
- Under 35, favorable prognosis: one
- 35 to 37: one strongly encouraged, two within the limit
- 38 to 40: no more than two
There’s no federal rule against DET, so clinics set their own policies. The guidance also allows deviation, and requires the justification to be documented in the medical record: age, embryo quality, prior history, prognosis.
Two embryos doesn’t mean two babies
Twins require both embryos to implant, so the twin rate tracks how likely each embryo is to take. Younger patients with good embryos have a higher chance of both sticking. Older patients often have one implant, or none.
In one study of over 2,000 women aged 35–45 who had double embryo transfers, 816 became pregnant, and 192 of those pregnancies were twins.
In another study of about 15,000 women who had double embryo transfers, twin rates tracked embryo quality:
- two good-quality embryos –> 26% twins
- one good, one less –> 12.8%
- neither graded good –> 9.3%
These are all conditional on the transfer working. They’re the chance of twins given that a pregnancy happened, not the chance of twins per transfer, which is lower.
Risks of a twin pregnancy
Most twins go home healthy. The risk isn’t that twin pregnancies usually go badly. It’s that the share going badly is much larger.
A twin pregnancy is categorized as high-risk. ACOG identifies preterm birth as its most consequential complication. Over half of twins are born before 37 weeks, against roughly 10% of singletons.
A full term pregnancy starts at 39 weeks. 37-39 weeks is early term. Anything before 37 weeks is preterm, and has high risks of complications include breathing difficulties, heart problems, brain bleeding, trouble maintaining temperature, infections, and feeding challenges. These health issues happen because a baby’s organs are not fully ready for life outside the womb.
In a Norwegian registry study of over 480,000 women, where the singleton preterm baseline is lower than in the US, over half of twin pregnancies were delivered preterm, against about 6% of singletons.
| Twins | Singletons | |
|---|---|---|
| Late preterm (34-37 wks) | 33.0% | 4.3% |
| Very preterm (28-34 wks) | 18.2% | 1.4% |
| Extremely preterm (under 28 wks) | 3.6% | 0.4% |
Preterm birth drives most of the difference in newborn illness and death. Twins also raise the odds of low birth weight and NICU admission. Additionally, the second twin fares worse than the first on nearly every measure: stillbirth, early neonatal death, low birth weight, and NICU admission.
For the carrying parent, twin pregnancies raise the odds of pre-eclampsia, gestational diabetes, cesarean delivery, and postpartum hemorrhage. Severe maternal complications and maternal death were significantly higher in twin pregnancies than singleton pregnancies across every region studied.
The field has moved accordingly. A decade ago, about one in five IVF deliveries was a multiple. By 2024, close to 97% of IVF births were singletons, near the rate for pregnancies conceived without treatment.
The other way to use two embryos
Considering twins means transferring two embryos in one cycle. A different comparison worth considering is transferring one embryo in two cycles — a single embryo once, and if that fails doing another one later.
A meta-analysis pooling 12 studies covering about 198,000 women compared those two paths. The cumulative live birth rate was virtually the same. However, the gap in twins was not close at all.
| Two embryos | Both at once | One, then the other |
|---|---|---|
| Chance of a baby | 48.9%Across the whole path | 48.2%Across both transfers |
| Chance of multiples | 17.7% | 0.9% |
For someone with two viable embryos, the trade isn’t twins against one baby. It’s the same chance of a baby, arranged as one riskier pregnancy or two safer attempts.
Bottom line
A clinic may or may not agree to transfer two embryos at the same time, at least not without a discussion on risks, especially if you’re older or have fewer or lower-quality embryos. What you can’t do is guarantee twins. For a good-prognosis patient, the consensus is clear: one embryo at a time gives a similar chance of a healthy baby with far less risk. If the goal is two children, two singleton pregnancies is the safer route than one twin pregnancy.
Sources
- American Society for Reproductive Medicine, “Guidance on the limits to the number of embryos to transfer: a committee opinion (2021)”
- American College of Obstetricians and Gynecologists, “Multifetal Gestations: Twin, Triplet, and Higher-Order Multifetal Pregnancies (Practice Bulletin 231)”
- Society for Assisted Reproductive Technology, “National Summary Report”
- BMC Pregnancy and Childbirth, “Risk factors for twin pregnancy in women undergoing double cleavage embryo transfer”
- PeerJ, “The effect on twinning rate of transferring double vitrified-warmed embryos in women of advanced reproductive age: a retrospective study”
- BJOG: An International Journal of Obstetrics and Gynaecology, “Different pathways for preterm birth between singleton and twin pregnancies: a population-based registry study of 481,176 nulliparous women”
- Frontiers in Endocrinology, “Effectiveness and Safety of Two Consecutive Cycles of Single Embryo Transfer Compared With One Cycle of Double Embryo Transfer: A Systematic Review and Meta-Analysis”
- New England Journal of Medicine, “Elective Single-Embryo Transfer versus Double-Embryo Transfer in in Vitro Fertilization”
- BMC Pregnancy and Childbirth, “Perinatal outcomes in twin pregnancies complicated by maternal morbidity: evidence from the WHO Multicountry Survey on Maternal and Newborn Health”