How Twin Pregnancies Increase the Risk of Birth Injury

Twin pregnancies bring joy and excitement, but they also carry higher medical risks than singleton pregnancies.

When you’re expecting twins, your doctors should provide closer monitoring throughout pregnancy and labor, not to alarm you, but to help your care team spot potential problems early and respond appropriately.

Understanding what monitoring should show at each stage can help you know what to expect and recognize when something may need a closer look. Not every complication is preventable, but proper surveillance can make a real difference in catching warning signs before they lead to serious harm.

Why Twin Pregnancies Are Considered Higher Risk

Twin pregnancies are classified as high-risk because they involve more frequent complications than singleton pregnancies: preterm birth, growth differences between babies, placental complications, and positioning problems that can complicate delivery.

Preterm birth is the most significant factor; twins are considerably more likely to be born before 37 weeks, and earlier delivery raises the risk of breathing problems, feeding difficulties, and developmental challenges.

Growth restriction can affect one or both twins, sometimes from unequal placental sharing or blood flow problems, and fetal distress during labor is also more common with twins, partly from positioning challenges and the increased physical demands on the mother’s body.

None of this means every twin pregnancy will have problems; many families welcome healthy twins without serious complications. It’s why closer monitoring than a singleton pregnancy is standard practice, not a sign that something’s already wrong.

Why Chorionicity Matters So Much

Chorionicity, the number of placentas your twins share, is one of the most important pieces of information your care team should establish early, ideally in the first trimester; guidelines call for dating between roughly 11 and 14 weeks, though chorionicity can often be identified as early as 8 weeks in experienced hands.

This single determination drives essentially the entire surveillance plan for the rest of your pregnancy.

Dichorionic twins each have their own placenta and amniotic sac. They may be fraternal or identical, but because they don’t share blood supply, they generally carry lower risk than monochorionic twins, though still meaningfully more than a singleton pregnancy.

Monochorionic twins share a single placenta and its blood vessels. This creates specific risks unique to the shared circulation, most notably twin-to-twin transfusion syndrome, where blood flow becomes unbalanced between the babies. Roughly 20 percent of twin pregnancies are monochorionic, and this shared-placenta arrangement is why monochorionic twins need meaningfully more intensive surveillance than dichorionic twins throughout pregnancy.

What Routine Ultrasound Monitoring Should Show

Monitoring frequency and focus should depend on chorionicity and whether complications have already been identified.

For dichorionic twins, growth ultrasounds typically occur about every four weeks starting around mid-pregnancy, measuring each baby’s growth, checking amniotic fluid around each baby, and assessing placental position and appearance, with measurements compared between the two babies to flag significant growth differences.

For monochorionic twins, the surveillance picture has two separate pieces worth understanding, since they’re not the same interval. According to the Society for Maternal-Fetal Medicine’s updated February 2026 special statement on monochorionic twin management, growth assessment for an uncomplicated monochorionic pregnancy is now specified at every four weeks, a change from the 2020 checklist’s every two-to-four-week range.

Your ultrasound reports should document specific measurements for each baby, head circumference, abdominal circumference, femur length, and estimated fetal weight, along with amniotic fluid around each baby and whether fluid levels are balanced or significantly different between the twins.

What Doctors Look For in Twin Growth Scans

Growth monitoring identifies whether both babies are developing appropriately or whether one or both are falling behind. Significant growth discordance, where one twin is noticeably smaller than the other, can indicate placental problems or unequal nutrient distribution.

Your doctors should calculate estimated fetal weight for each baby and compare them; a difference of roughly 20 percent or more between twins is a commonly used threshold that may warrant additional testing or closer monitoring, though some size difference between twins is normal on its own.

When growth restriction is suspected, additional Doppler studies may be ordered to evaluate blood flow; abnormal findings can suggest the placenta isn’t functioning properly or one baby isn’t receiving adequate oxygen and nutrients.

Growth trends over time matter more than any single measurement; a baby who’s small but growing consistently is generally less concerning than one whose growth rate is visibly slowing.

What TTTS Monitoring Should Look For

Twin-to-twin transfusion syndrome develops in an estimated 10 to 15 percent of monochorionic pregnancies, when blood vessel connections in the shared placenta create an imbalance, one baby receiving too much blood, the other too little.

It’s typically staged using the Quintero system based on how the condition progresses.

Signs doctors watch for include a significant difference in amniotic fluid between the two sacs, one baby with too much fluid and the other too little, along with size differences, abnormal Doppler findings, and signs of cardiac strain in either baby.

Our guide on twin-to-twin transfusion syndrome covers the condition itself, staging, and treatment options like laser surgery and amnioreduction in full detail.

What Fetal Movement Concerns Can Mean

As pregnancy progresses, you may be asked to track fetal movement for each baby, which can be genuinely challenging with twins.

Reduced movement in one or both babies should prompt evaluation, typically a nonstress test or biophysical profile assessing heart rate patterns, breathing movements, body movements, muscle tone, and amniotic fluid.

If one baby’s movement noticeably decreases, or you’re unsure whether you’re feeling both babies move, contact your doctor rather than waiting for your next scheduled visit.

Many movement concerns turn out to be normal variation, but some point to placental, cord, or fetal problems that need prompt attention.

What Monitoring Should Show During Labor

Labor and delivery bring their own challenges for twins. Continuous fetal heart rate monitoring for both babies is standard throughout labor, helping the care team identify distress and respond quickly.

This is technically more demanding with twins, since the monitors must track two separate heart rates simultaneously, and your team should confirm both babies are being monitored consistently and distinguishably from each other.

Normal patterns show variability and appropriate responses to contractions. Concerning patterns include a persistently rapid or very slow heart rate, repetitive decelerations, or a lack of normal variability, any of which can suggest a baby isn’t receiving enough oxygen.

Twins also face higher risk of umbilical cord compression and positioning problems during labor, and the second-born twin can experience additional stress as the uterus contracts more forcefully once the first baby is delivered.

When Abnormal Monitoring May Require More Testing or Delivery

Not every abnormal finding calls for immediate delivery, but your team should have a clear plan for responding to concerning results, one that depends on how severe the finding is, your gestational age, and whether it’s affecting one or both babies.

Mild abnormalities may warrant closer observation or additional testing. More significant concerns, severe growth restriction, very low amniotic fluid, reversed Doppler flow, or persistent abnormal heart rate patterns, may call for hospitalization or prompt delivery.

If delivery is recommended early, your team should walk through how they’re weighing the risks of prematurity against the risks of continuing the pregnancy, and steroid injections to help mature the babies’ lungs are often given before a planned early delivery.

How Birth Injury Concerns Can Arise When Problems Are Missed or Delayed

Birth injuries in twin pregnancies can happen even with fully appropriate care, but some are linked to monitoring failures or a delayed response to warning signs, missed signs of fetal distress, missed significant growth discordance, delayed testing, or an inadequate response to abnormal findings once they appeared.

Oxygen deprivation during pregnancy or labor can lead to hypoxic-ischemic encephalopathy, which depending on severity and duration can result in developmental delays, cerebral palsy, seizure disorders, or other long-term disabilities.

In New York, a medical malpractice claim requires showing that care fell below accepted standards and that this departure caused harm, evaluated through a careful review of medical records, monitoring strips, ultrasound reports, and the actual timeline of events.

Families generally have two and a half years from the date of the malpractice to file a claim under CPLR 214-a, with CPLR 208 allowing that deadline to be tolled for a minor child up to ten years from the date of the malpractice.

Since the specific timeline depends on the facts of the case, it’s worth confirming with an attorney directly.

Frequently Asked Questions

How Often Should Monochorionic Twins Actually Be Monitored, Growth Versus TTTS Screening?

These run on two different schedules. Per SMFM’s current guidance, growth assessment for an uncomplicated monochorionic pregnancy is generally every four weeks. Screening specifically for twin-to-twin transfusion syndrome, checking amniotic fluid and bladder filling, typically continues every two weeks starting around 16 weeks, since TTTS can progress faster than general growth changes would reveal.

What Growth Difference Between Twins Actually Warrants Concern?

A commonly used threshold is roughly a 20 percent or greater difference in estimated fetal weight between the two babies, though this isn’t an automatic red flag on its own; your doctors should weigh it alongside amniotic fluid levels, Doppler findings, and the overall growth trend over time rather than a single measurement.

Is TTTS the Same as Ordinary Twin Growth Discordance?

No, though they can look similar early on. TTTS specifically involves a placental blood-vessel imbalance in monochorionic twins, marked by discordant amniotic fluid, not just discordant size. Ordinary growth discordance can happen in either monochorionic or dichorionic twins from unequal placental sharing without the specific vascular imbalance that defines TTTS.

Should I Push Back if My Doctor’s Monitoring Schedule Seems Less Frequent Than I Expected?

It’s reasonable to ask why a particular schedule was chosen, especially since monochorionic surveillance recommendations have genuinely changed in recent guideline updates. Confirming your twins’ chorionicity and asking your provider to explain how that determines your specific schedule is a fair, direct question, not something to feel awkward about raising.

What Should I Do If I Think a Warning Sign Was Missed During My Twin Pregnancy?

Request your complete medical records, every ultrasound report and image, Doppler results, nonstress tests, and labor monitoring strips, not just a summary. Reviewing the documented timeline against when concerns should have been identified is the starting point for understanding whether monitoring matched your specific risk profile.

Moving Forward With Confidence and Information

Understanding what monitoring should show at each stage, and how much that schedule depends on a single early determination like chorionicity, can help you feel more informed and prepared rather than anxious.

Most twin pregnancies progress well with appropriate surveillance. If you’ve experienced a difficult outcome and wonder whether monitoring fell short of what it should have been, gathering your medical records and speaking with professionals who understand both the medical and legal sides of twin pregnancy care can help you find real answers.

This article is for informational and educational purposes only. It is not a substitute for medical advice from your healthcare providers or legal advice based on your family’s specific circumstances.

Was Your Baby Injured by Medical Negligence? If you believe a delay in diagnosis or a missed warning sign affected your child’s care in New York, our team can review your medical records and explain your options at no cost. Call 833-99-BIRTH or request a free case review.