16 Week Scan
The sweet spot for gender determination on ultrasound, and a relaxed mid-pregnancy reassurance window between the NHS dating scan and the anomaly scan.
Quick Answer
At a 16 week scan, baby's gender can be determined with 99%+ accuracy on ultrasound (provided baby is in a cooperative position). The fetus is around 12cm long and looks unmistakably human, with a recognisable face, all four limbs, and plenty of movement on screen. The placenta is fully functional, the heartbeat is strong and easy to detect, and many mothers will start to feel the first flutters of movement (quickening) around this time. At Numi Scan Gateshead, a 16-week Gender Baby Scan costs £68 or our Luxury Gender Reveal Baby Scan package is £95.
What's Happening at 16 Weeks
By 16 weeks your baby is roughly the size of an avocado, about 12cm from head to bottom and weighing around 100 grams. The growth pace has slowed slightly compared to the explosive first trimester, but development continues to refine. Baby's skin is paper-thin and translucent, with the network of blood vessels visible underneath. Lanugo, the fine downy hair that covers the body, has started to appear. Eyebrows and eyelashes are forming. The bones, which began as soft cartilage, are gradually hardening into the skeleton baby will be born with.
The senses are coming online. Baby can now hear muffled sounds from outside the womb (your voice, music, the rumble of traffic), and from this point onwards, hearing develops rapidly. The eyes can detect light through the fused eyelids, even though they won't open until around 28 weeks. The mouth can suck, the hands can grasp, and there's plenty of movement: kicking, rolling, hiccupping, sometimes even thumb-sucking. Most first-time mothers won't feel these movements yet (quickening typically arrives at 18–22 weeks for first pregnancies, earlier for subsequent ones), but you'll see plenty of action on the ultrasound screen.
The reproductive anatomy is now fully differentiated and clearly visible on a high-quality 2D ultrasound. This is why 16 weeks is widely considered the sweet spot for gender determination on a Gender Scan: the genital tubercle has formed unambiguously, but baby isn't yet so big that positioning becomes a problem (which can happen in the third trimester).
Gender Determination at 16 Weeks
The most common reason parents book a 16-week private scan is to find out whether they're having a boy or a girl, and 16 weeks is genuinely the right gestation for it. Earlier, at 12 weeks, the genital tubercle is forming but hasn't differentiated enough for confident identification (accuracy is only around 70–75% at 12 weeks, which most sonographers consider too low to call). By 15 weeks accuracy climbs to roughly 95%. By 16 weeks, with an experienced sonographer and a cooperative baby, accuracy is 99%+.
The dependency is baby's position. If baby is lying with legs crossed, sitting on their bottom, or has a hand strategically placed, the view of the genital area can be obscured. When this happens we'll usually try gentle repositioning techniques (asking you to walk around for a few minutes, having a sip of cold water, lying on your side) and if baby still won't cooperate we'll invite you back for a free recheck the following week.
If position-dependency feels too uncertain, our DNA-based Gender Blood Test from 8 weeks is an alternative: it's 99% accurate, doesn't depend on baby's position, and gives results from much earlier in pregnancy. Many parents who want absolute certainty at the earliest possible moment combine the DNA test with a Luxury Gender Reveal scan at 16 weeks for the visual confirmation.
Scan Packages for Week 16
Gender Baby Scan
From 15 weeks
Standard 20-minute gender confirmation scan with photos and digital images. The straightforward option.
View package →Luxury Gender Reveal Baby Scan
From 15 weeks
Extended scan with confetti cannon, sealed envelope option, gender card, photos and digital images. The full reveal experience.
View package →Early Gender Blood Test (DNA)
From 7 weeks
Lab-based DNA gender test, 99% accurate from 7 weeks. Position-independent, perfect alongside an ultrasound for absolute certainty. £125 blood test only, or £175 with an early pregnancy scan.
View package →Book Your 16 Week Scan
Same or next-day appointments often available. CQC-regulated, experienced and registered sonographers.