A normal NT (nuchal translucency) measurement and a raised uterine artery Doppler PI (pulsatility index) on the same scan aren't contradictory — they're measuring two entirely different things. The NT measurement is part of chromosomal-risk screening; the uterine artery Doppler looks at blood flow resistance in the vessels supplying the placenta, and a raised PI is a recognised marker for closer monitoring later in pregnancy, not a chromosomal finding.

What each measurement is actually screening for

  • The NT scan measures the fluid-filled space at the back of the baby's neck, and combined with blood tests, estimates the chance of chromosomal conditions like Down syndrome. A normal NT lowers that specific risk.
  • The uterine artery Doppler measures how easily blood flows through the arteries that supply the placenta. A raised pulsatility index (PI) means there's more resistance in that blood flow than expected at this stage of pregnancy — a sign the placenta may not be forming its blood supply as efficiently as usual.
  • These two measurements are done at the same visit in many first-trimester screening protocols precisely because they flag different, unrelated risks — a normal result on one doesn't tell you anything about the other.

What a raised PI is actually a marker for

A raised uterine artery Doppler PI in the first trimester is an established risk marker, most notably for:

  • Pre-eclampsia later in pregnancy (particularly earlier-onset pre-eclampsia)
  • Fetal growth restriction, where the baby grows more slowly than expected because the placenta isn't supplying blood as efficiently

It's important to be clear about what this means: a raised PI increases the statistical chance of these complications developing — it does not mean they will happen. Many pregnancies with a raised first-trimester PI go on to be entirely uneventful, which is exactly why this is used as a screening tool that changes monitoring, not a diagnosis on its own.

What usually happens next

  • Closer blood pressure monitoring through the rest of the pregnancy, since pre-eclampsia is diagnosed partly through blood pressure trends over time
  • Additional growth scans later in pregnancy to check the baby is growing as expected, since this is the other main complication the marker flags
  • A conversation with your doctor about low-dose aspirin, which has been shown to reduce pre-eclampsia risk in women identified as higher-risk by first-trimester screening — but this only works if started early (generally before 16 weeks), which is part of why this Doppler result is checked in the first trimester rather than later
  • Your overall risk profile matters alongside the Doppler result — your doctor will weigh this finding together with your blood pressure history, any prior pregnancy complications, and other screening results, rather than treating the PI number in isolation

A raised uterine artery PI with an otherwise normal NT scan is a reason for a more closely monitored pregnancy, not a cause for alarm about the baby's chromosomes or current development. The entire point of catching this early is that it opens the window for preventive steps, like aspirin, that only work if started in the first trimester.

Frequently asked

Does a raised PI mean I will definitely develop pre-eclampsia?

No. It's a risk marker, not a diagnosis — many women with a raised first-trimester PI never develop pre-eclampsia, especially with the monitoring and preventive measures your doctor puts in place.

Should I start taking aspirin on my own because of this result?

No — aspirin dosing and timing in pregnancy should be decided by your doctor based on your full risk profile, not self-started. If it's appropriate for you, your doctor will prescribe it as part of your care plan.

Will this Doppler finding be repeated later in pregnancy?

Often yes, in the form of growth scans and sometimes repeat Doppler studies later on, since the point of flagging this early is ongoing monitoring rather than a one-time result.

Is this the same as a Doppler done later in the third trimester?

No — third-trimester Doppler studies (sometimes done on the umbilical artery or other vessels) are used differently, typically to check how a baby already suspected of growth concerns is coping, rather than to screen a low-risk-looking pregnancy for future risk the way the first-trimester uterine artery Doppler does.