20 Week Scan
The NHS anomaly scan week: the diagnostic gold standard for screening major fetal abnormalities. Here's what the NHS scan checks, how a private 20-week scan complements it, and what we see on screen at this stage.
Quick Answer
The 20 week scan is the NHS anomaly scan: a specialised screening scan that checks for 11 specific fetal conditions and is the diagnostic gold standard at this gestation. Baby is around 25cm long, weighing roughly 300 grams, with all major organs developed. Movement is felt by most mothers by now ('quickening'). A private 20-week scan complements (rather than replaces) the NHS appointment with longer time, family welcome, gender confirmation, photos and a relaxed atmosphere. At Numi Scan Gateshead a 20-week Wellbeing & Reassurance Baby Scan costs £65, or our Luxury Gender Reveal Baby Scan is £95.
What's Happening at 20 Weeks
Twenty weeks is the halfway mark of pregnancy and an extraordinary moment of completeness. Your baby is roughly the size of a banana, around 25 centimetres from head to heel, weighing about 300 grams. Every major organ has formed and is now refining function rather than building structure. The kidneys are producing about 7ml of urine an hour. The brain has formed all the neurons it will ever have, and they're now busy making connections at a phenomenal rate. The pancreas has begun producing insulin, the gallbladder is producing bile, and the digestive system is practising swallowing amniotic fluid.
Externally baby looks like a small, finished person. The skin has thickened from the translucent paper of earlier weeks and is now covered in vernix, a creamy white coating that protects baby's skin from the amniotic fluid until birth. Eyebrows and eyelashes are fully formed. Fingernails have grown to the tips of the fingers. The genitalia are unmistakable on ultrasound, which is one reason gender is reliably identifiable at this stage on a Gender Baby Scan or celebratory Luxury Gender Reveal Baby Scan. If your baby is a girl, her ovaries already contain millions of egg cells (a number that will actually decrease as she grows). If a boy, the testes have begun their slow descent from the abdomen, though they won't reach the scrotum until close to birth.
Most mothers can feel movement by 20 weeks, even first-time mothers; those tiny flutters that began at 17 or 18 weeks have grown into definite kicks and rolls. Baby has a sleep-wake cycle of 20–40 minute periods and is starting to respond to external sounds. This is the gestation at which playing music, talking, or singing to your bump genuinely starts to register on the other side.
The NHS Anomaly Scan: What It Checks
The NHS 20-week scan is formally part of the Fetal Anomaly Screening Programme (FASP) and is designed to screen for 11 specific conditions. The scan is performed by sonographers with specialist anomaly-screening training, takes 30–45 minutes, and is the most thorough single examination of fetal anatomy your baby will receive during pregnancy. It is, unambiguously, the diagnostic gold standard for this stage.
The conditions screened are: anencephaly, open spina bifida, cleft lip, diaphragmatic hernia, gastroschisis, exomphalos, serious cardiac abnormalities, bilateral renal agenesis, lethal skeletal dysplasia, Edwards' syndrome (trisomy 18), and Patau syndrome (trisomy 13). The scan also confirms the placenta's location (important for planning birth, since a low-lying placenta may need monitoring), assesses amniotic fluid volume, measures growth against expected ranges, and checks the umbilical cord.
If everything looks normal, the NHS sonographer will tell you so during the scan. If something is flagged, you'll be referred to a fetal medicine specialist for further investigation, usually a more detailed scan within 1–3 weeks. We strongly recommend you do not skip this NHS appointment, regardless of whether you're also having private scans. See our private vs NHS comparison guide for the full picture. It is the most clinically important single scan of your pregnancy.
Scan Packages for Week 20
Wellbeing & Reassurance Baby Scan
From 15 weeks
A 15-minute reassurance check between NHS appointments. Heartbeat, position, growth, photos and digital images.
View package →Luxury Gender Reveal Baby Scan
From 15 weeks
If your NHS trust didn't disclose gender, a celebratory reveal package with confetti, sealed envelope option, gender card, photos and digital images.
View package →Book Your 20 Week Private Scan
Same or next-day appointments often available. CQC-regulated, experienced and registered sonographers, a fast-growing wall of five-star reviews since 2024.