At 21 weeks pregnant (21+0 to 21+6 weeks, counted from the first day of your last period) you are about 4 months and 25 days along, moving from the 5th into the 6th month of pregnancy. Your baby is now heavier than the placenta and can hear sounds from outside the womb. If you have not had your detailed anomaly scan yet, the Turkish Ministry of Health guideline recommends it between 18 and 24 weeks.
Counted from your last period, 21 weeks pregnant is about 4 months and 25 days: the end of the 5th month and the start of the 6th. This week covers days 147 to 153 of pregnancy, and you are in the second trimester.
According to the NHS week-by-week guide, your baby is about 26.7 cm long from head to toe this week and is now heavier than the placenta. The placenta feeds your baby and removes waste, and it keeps growing throughout pregnancy to do its job.
Your baby's body is covered in a fine, downy hair called lanugo. It probably helps keep your baby at the right temperature and usually disappears before birth. Hair and eyebrows are developing too. Your baby can now hear noises and voices outside the womb, moves around a lot and is settling into patterns of sleeping and waking (NHS).
ACOG lists these developments for weeks 21 to 24:
As your bump grows, your centre of gravity shifts and your joints loosen, so you may feel a little unsteady. If you have a fall, try not to panic, as your baby is well protected, but let your midwife or doctor know as soon as you can (NHS).
Your baby may be wide awake just as you want to sleep. Try to catch up with short naps during the day.
The NHS lists these common symptoms at this stage:
A white, milky discharge is normal at this stage, but any bleeding should always be checked by a doctor (NHS).
There is no need to eat for two: you do not need extra calories until the third trimester, which starts at week 28. About 150 minutes of exercise a week is recommended in pregnancy; you could start with a brisk 10-minute walk each day (NHS).
Detailed anomaly scan. Recommended timing differs between organisations:
The same visit includes blood pressure and weight checks and repeat urine and blood tests; a womb size 4 cm larger or smaller than expected is a reason for referral. If you have had a preterm birth, your cervical length is measured, and after a caesarean or other womb surgery the placenta's position and attachment are checked.
Whooping cough (Tdap) vaccine. The Turkish guideline recommends the first Tdap dose between 18 and 24 weeks; if that window is missed, one dose can still be given until the end of week 32. Tdap has been offered to pregnant women in Turkey since 2 April 2025. The NHS usually offers it around week 20 and says it can be given from week 16 to week 32. UpToDate describes the US practice of giving it in every pregnancy, ideally between 27 and 36 weeks.
Coming up. The Turkish guideline asks that all women who are not in a high-risk group are told about glucose screening at 24 to 28 weeks, so you can plan that appointment now.
The anomaly scan checks how your baby's organs are developing and where the placenta lies (NHS, NICE). UpToDate adds that it also confirms how far along you are and looks at the placenta and cord, twins, cervical length and the baby's growth.
If your due date has not yet been set by ultrasound, this week matters: according to UpToDate, the due date from the earliest scan done by 21+6 weeks is final and is not changed by later scans. If no scan has been done by 22+0 weeks, the pregnancy is considered suboptimally dated.
How much does the baby weigh? In the reference table of the World Health Organization's fetal growth study across 10 countries (2017), the median (50th percentile) estimated weight at 21 weeks is about 398 g; the 10th percentile is 345 g and the 90th percentile 458 g. These are reference values, not your own baby's measurement. The study notes differences between countries, maternal characteristics and the baby's sex, so these charts may need adjusting for local use. The growth trend matters more than a single measurement. According to UpToDate, scans done to estimate the baby's weight are generally not useful before about 24 weeks.
| Symptom | Usually | Seek care if |
|---|---|---|
| Pulling or stabbing pain in the groin or sides of the bump | Pain from the womb's ligaments stretching is common at this stage. | Get help straight away if the pain is severe, comes with bleeding, or comes with regular tightenings, period-like cramps, new low backache and pelvic pressure (NHS, UpToDate). |
| Vaginal discharge | A white, milky discharge is normal in pregnancy. | Get help straight away if clear fluid is leaking, if there is bleeding, if the discharge smells bad, or if you have a fever (Turkish Ministry of Health guideline, 2026). |
| Feeling unsteady or having a fall | This happens because your centre of gravity shifts and your joints loosen; your baby is well protected in the womb. | Tell your midwife or doctor if you fall (NHS); get help straight away if you have tummy pain, bleeding or leaking fluid. |
Contact your midwife, doctor or maternity unit straight away if you have:
Most of these are danger signs or emergency referral criteria in the Turkish Ministry of Health Antenatal Care Management Guideline (2026); tightenings, cramps, backache and pelvic pressure are on UpToDate's list of preterm labour signs. Headache, vision problems, facial swelling, pain below the ribs and high blood pressure can be signs of pre-eclampsia (NHS, UpToDate). The NHS says to call if your baby's movements reduce, stop or change, without waiting until the next day, even at night.
The NHS says the sonographer may be able to tell you, but it is sometimes hard to get a proper look, and some hospitals do not reveal the sex before birth. If you would rather not know, say so before the scan starts.
It can be. The RCOG says most women first notice movements at 18 to 20 weeks; in a first pregnancy it may be later than 20 weeks, and women who have been pregnant before may feel them as early as 16 weeks. Thresholds differ: the NHS asks you to tell your midwife if you have felt nothing by 24 weeks, while the Turkish Ministry of Health guideline lists no movements after 20 weeks as a reason for referral to an obstetrician.
A pulling feeling on the sides of the bump or in the groin, from the womb's ligaments stretching, is one of the common symptoms the NHS lists for this week. Severe pain, bleeding, regular tightenings or increasing pelvic pressure are not expected; get help straight away if you have them.
No, bleeding should always be checked. The NHS advises seeking medical advice for any bleeding. NICE recommends hospital review for unexplained bleeding after 13 weeks, with anti-D for women who are rhesus negative.
In the reference table of the World Health Organization fetal growth study (2017), the median estimated weight at 21 weeks is about 398 g, with the 10th percentile at 345 g and the 90th at 458 g. These are reference values; an ultrasound weight is itself an estimate with a margin of error, so the growth trend matters more than a single measurement.
Last updated: . All sources have been confirmed with their latest versions. This content is for educational purposes and is not a substitute for a doctor's examination.