High Risk Pregnancy /
Maternal Fetal Medicine

Fetal anomaly can be detected at the combined first trimester screening (cFTS) at 12 weeks of pregnancy or at the detailed fetal anomaly screening at 20 weeks of pregnancy. Rarely, certain fetal anomalies (especially brain or intestinal) may only be detected in the third trimester. Accurate prenatal diagnosis can be performed with high quality ultrasound scans. Invasive genetic tests may be required to establish the cause of the anomaly.

Early onset Fetal Growth Restriction can occur before 32 weeks of pregnancy whilst Late onset Fetal Growth Restriction usually occurs after 32 weeks of pregnancy. Measuring the blood flow in the umbilical cord and fetal brain by colour Doppler ultrasound optimizes the timing for delivery so as to achieve optimal outcomes for the pregnancy.

Screening can be performed in the first trimester together with Down syndrome screening. This test combines a high resolution ultrasound scan measuring the blood flow in the uterine arteries together with screening of a maternal blood sample and measuring the blood pressure. This is done between 11 and 14 weeks of pregnancy.

Instituting early treatment, adequate monitoring and care will allow optimal timing of the delivery. These measures will help to reduce adverse outcomes.

Preterm birth is when the delivery occurs before 37 completed weeks of pregnancy. Measuring the cervical length (by a transvaginal ultrasound scan) gives an indication of the risk of preterm labour and is best incorporated into the Fetal Anomaly Scan. Early detection of those at risk may help to avoid preterm labour by active intervention. Consult our doctors to discuss optimal treatment either by medical treatment or surgical intervention (cervical cerclage).

Amniocentesis is a procedure whereby amniotic fluid is collected via a small needle puncture into the amniotic sac. The purpose is to collect the amniotic fluid for genetic tests or other tests depending on the clinical indications. This procedure is done from 16 weeks pregnancy onwards.

Chorionic Villus Sampling (CVS) is a procedure whereby placental tissue biopsy is done. A small needle is inserted into the placenta and chorionic villi collected. The purpose is for genetic tests. This procedure is done from 11 to 14 weeks pregnancy onwards.

Both Amniocentesis and CVS are considered invasive diagnostic procedures. The risks include rupture of membranes, bleeding, infection, injury to nearby organs and fetal loss/miscarriage (0.3%). These procedures are done under continuous ultrasound guidance to minimize risks to the fetus and the mother. Prof George SH Yeo and Dr Edwin WH Thia are both accredited to perform Amniocentesis and CVS. They are also the approved trainers for obstetric related invasive procedures at KK Hospital.

Twins or Higher Order Multiple Pregnancy are considered higher risk pregnancies as more complications may arise as compared to a singleton (one baby) pregnancy. They are at a higher risk for general pregnancy complications such as miscarriage, fetal anomalies, fetal growth restriction and preterm labour.

Twins can be identical or non-identical. In identical (monozygotic) twins, one egg is fertilised by one single sperm, but the egg divides into two embryos soon afterwards. Thus, both twins have the same genetic material and will have the same sex with perfect resemblance. The identical twins can share one placenta (“mono-chorionic”) or have two different placentas (“di-chorionic”). They can be housed in one water sac (“mono-amniotic”) or two separate water-sacs (“di-amniotic”).

It is important to know whether the twins share one placenta or have two different placentas as monochorionic twins have higher risk for complications. The distinction between high-risk monochorionic and lower-risk dichorionic twin pregnancies can be accurately achieved in the first-trimester scan, because the amnion and chorion are still separated from one another. Later in gestation, because of the close apposition of amnion and chorion, it becomes much more difficult to accurately determine chorionicity. Hence, the importance of first-trimester chorionicity determination cannot be stressed enough.

Unique complications can arise from monochorionic twins. These include twin to twin transfusion syndrome (TTTS), selective fetal growth restriction (sFGR), twin anaemia-polycythaemia sequence (TAPS) and twin reversed arterial perfusion (TRAP) syndrome. Early diagnosis and timely management can substantially improve the prognosis of monochorionic twin complications. It is highly recommended that monochorionic twins be followed up every two weeks with high resolution ultrasound to detect early signs of complications.

Placenta previa is a condition when the placenta lies low in the uterus and partially or completely covers the cervix. Placenta previa can cause massive bleeding during the pregnancy and during labour. It is important to determine the location of the placenta during the pregnancy by ultrasound scans. For patients with placenta previa, it is important to monitor for bleeding and you will need a caesarean section to deliver your baby.

Placenta accreta is a serious condition when the placenta grows too deeply into the uterine wall. Patients with a previous caesarean section delivery have a higher risk for developing this condition. There is a high risk of severe bleeding after delivery. Some patients may have severe bleeding during pregnancy. Ultrasound assessment can provide accurate prenatal diagnosis allowing the surgeon to prepare during the delivery.

Placenta accreta can be detected early in the first trimester using high resolution transvaginal ultrasound. Patients with previous caesarean section deliveries should undergo a transvaginal ultrasound in the first trimester to assess for the risk for placenta accreta.

Fetal therapy involves a therapeutic intervention for the purpose of correcting or treating a fetal anomaly or condition. Example of fetal therapy includes:

• Intrauterine blood transfusion for the treatment for fetal anaemia
• Fetoscopic Laser Photocoagulation for Twin to Twin transfusion syndrome (TTTS)
• Fetal thoraco-amniotic shunt insertions for the treatment for fetal pleural effusions
• Fetal bipolar cord coagulation for discordant fetal anomaly, severe selective fetal growth restriction or severe TTTS in monochorionic twin pregnancies.

Medical disorders may develop during pregnancy. Common medical problems like gestational diabetes and preeclampsia can manifest in the second half of the pregnancy. It is important to screen for these diseases and to detect them early to reduce adverse outcomes.

Screening for preeclampsia can be done early in the first trimester. This test combines a high resolution ultrasound scan measuring the blood flow in the uterine arteries together with screening of a maternal blood sample and measuring the blood pressure. Screen positive patients can start aspirin to effectively reduce their risk of developing preeclampsia.