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Pregnancy Bliss | Reproductive Health Hub

In case of previous loss of pregnancies through stillbirth, should the mother expect blood-flow to be measured at this stage?
Measuring blood-flow (usually using Döppler ultrasound) has no useful purpose at this stage of pregnancy, and absence of this test should be no cause for panic.

If the placenta is reported to be low at twenty weeks, should a repeat scan be offered; and, if so, at what gestation?
In practise, practically every woman found to have a low-lying placenta at 20 weeks is offered a repeat scan later on in pregnancy. Mothers found this reassuring and that is a valid reason for the service. There is probably no compelling medical need to repeat a scan for this indication. Exceptions can be made in special situations. These will include:

Where the placenta is actually overlying the cervix, so the risk of placenta praevia later in pregnancy is probably significant

History of previous placenta praevia, as the expectant mother will be understandably anxious and because of the tendency of this condition to occasionally recur.

Repeat scans could also be considered in cases of multiple pregnancy (twins, triplets etc.), smoking and drug abuse and previous caesarean section. Even here, the usefulness is debatable.
The most important thing to remember is that, for the vast majority of women reported to have a low-lying placenta at twenty weeks, this finding is of no lasting consequence, as the placenta will be in a normal position within weeks. If a repeat is to be done, most units perform this at about 32 to 34 weeks, unless there are clinical indications to do it earlier.
Vaginal bleeding is normally the indication for an unscheduled repeat scan.

Drawbacks of scanning

Are there any drawbacks from routine scans at twenty weeks?
Unfortunately, yes. As mentioned earlier, sometimes there are findings that are clearly abnormal but whose significance cannot be established until delivery.
Such findings include abnormal abdominal shadows; cysts in the brain; "low-lying" placenta; and increased or reduced fluid volume.

Such findings quite understandably cause anxiety, not least because the causes remain unexplained.

Such mothers should draw comfort from the fact most of them will have perfectly normal babies at the end of the day. Unfortunately, there has to be closer monitoring of the pregnancy, in an effort to identify those pregnancies which might require specific action or intervention.

The final word?
Most mothers will have a perfectly normal scan with normal findings all round. A few will have some great surprises, such as unexpected twins; fewer still will have devastating findings such as a non-viable pregnancy or a fetus that has a condition incompatible with life. One in fifty will find that their baby has a gross abnormality that may require surgical correction soon (or later) after birth.

The puritan will point to the fact that we have to scan ten women to detect anything useful in one. This is ignoring the fact that the other nine will have got to see and know their baby for the first time – not something to be sniffed at.

Early trimester Placenta and fluid 20 weeks scan Safety Uses in pregnancy Limitations 4D scans Fetal gender