Episode 23 28-week Antenatal Visit

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Hello, my name's Dr Elizabeth McCarthy, known as Liz, and I'm an obstetrician, sub-specialist in maternal fetal medicine and heavily involved in teaching women's and newborn health at the University of Melbourne. This podcast is about what happens in antenatal clinic for women around 28 weeks.

It's a milestone visit, and you as medical students can meet quite a few patients at this stage of their pregnancy. Women may be waiting in the hospital for about two hours to fit in a visit and the three blood collection times for a glucose tolerance test, and some women have an anti-D injection too.

As usual, the antenatal visit concerns two patients, the pregnant woman and the unborn baby. It concerns clinical assessment, health education, and planning for what next.

I'll use the term 28-week visit as shorthand for a visit early in the third trimester. It can be any time between 26 to 30 weeks.

The tests at this visit are slightly different from the screening tests at the booking visit. The 28-week routine tests for most pregnant women in Victoria in Australia in 2022 are: first, a glucose tolerance test, second, full blood examination, and third, a check on blood group antibodies. Depending on local epidemiology, this can be a good time to rescreen for syphilis with serology as well.

Now to learn about antenatal care in other settings, lower resource settings, I strongly recommend searching video websites for FANC, meaning focused antenatal care. You'll see that commonly in FANC there is a 26-week visit, which is the second of four recommended FANC visits. And the range of tests in the FANC setting also varies according to local priorities for maternal and child health. But typically, FANC is an opportunity to test for HIV, prevent malaria, treat hookworm, complete tetanus immunization, and give out nutritional supplements.

Returning to the Australian antenatal clinic and the 28-week milestone visit, first, we'll concentrate on the pregnant women here. Now, many women fit in their antenatal care alongside work and other unpaid tasks. They're busy people.

In the Australian setting, healthy women often start maternity leave around 34 weeks, but that's about six weeks after the 28-week visit, which is the topic of the current podcast. So practically, the woman might need a work certificate for her attendance at antenatal clinic today.

Concerning maternal symptoms at or before 28 weeks, women will start to notice a pattern of fetal movements for many hours every day. Ask the woman what it feels like. Ask her to note what's normal for her baby.

If she's concerned about reduced fetal movements, or RFM, she should understand clearly how to get further assessment of fetal well-being on the same day she's worried. Don't get her to wait for another scheduled review. Many episodes of reduced fetal movements are benign, but some indicate a sick fetus, for example, due to worsening placental insufficiency. And in this case, timely assessment can prevent stillbirth.

Some women by the third trimester have pelvic girdle pain. Others have gastroesophageal reflux or other discomforts. As usual, assess any symptom with a careful history and targeted examination.

In the absence of symptoms or an approach to a problem, perform a routine examination. This comprises blood pressure in the seated position, abdominal examination, and urinalysis for proteinuria.

So concerning fetal well-being, as discussed, maternal perception of fetal movements is very reassuring. On abdominal examination, the fundal height will normally be 28 centimetres plus or minus 2 centimetres. You can try to determine the presenting part by palpation.

About 25% of cases won't yet have a stable cephalic presentation. Breach presentation and transverse lie are quite common at 28 weeks, but not of concern unless premature birth unexpectedly occurs.

Urinalysis is an extension of bedside clinical assessment. Women can learn to check this for themselves. Proteinuria can indicate two important complications, bacteria or preeclampsia. The latter, preeclampsia, is uncommon at 28 weeks but becomes increasingly common with advancing gestation.

28 weeks is the usual time to screen for gestational diabetes, which is why I started this podcast with the phrase, “that sugar drink”. This is a time when we test for women who don't have pre-pregnancy diabetes. It's a perfect time to test. It's not too late to intervene in the interest of fetal well-being and it's not too early to miss the third trimester when the placenta is pouring out anti-insulin hormones, such as human placental lactogen or HPL.

What test? Well, for the last 20 or more years, it's quite clear that the oral glucose tolerance test is the best validated test for diabetes in pregnancy. It's better than alternatives such as haemoglobin A1c, fasting or random glucose measurements and so much more accurate than urine testing for glycosuria.

So just a bit of a note, haemoglobin A1c is actually artificially reduced in pregnancy related to high maternal red cell turnover and its reflection of a three-month glucose pattern isn't quite so important in pregnancy. We are actually on a shorter time frame and more interested in day-to-day fluctuations.

Fasting or random glucose tests may be attractive to the woman who wants to avoid the sugar drink, which many women find unpleasant to the point of vomiting. However, the full three blood tests, fasting one hour and two hour from the OGTT, give more information for an accurate GDM diagnosis.

In current practice, around 15% of women are diagnosed with gestational diabetes or GDM for short. Most women with GDM can achieve good glycemic control with diet and exercise and a minority need to add in medications. You'll have tutorials and other learning activities about GDM in more detail.

Another 28-week blood test is for haemoglobin or full blood examination. By this stage of pregnancy, iron reserves may be reduced because the fetus draws avidly on maternal stores. And it's actually an important test, both in high-resource settings as well as globally, so in the antenatal clinic you'll attend as well as in FANC. It's important that all women approaching birth are not anaemic.

Now, assessing haemoglobin and red cell indices is actually an efficient use of resources, more efficient than using iron study tests for every pregnant woman.

Iron supplementation can be given orally, for example, every second day, to aid absorption and improve the cytoprofit profile compared with daily or multiple tablets of iron per day.

The remaining usual 28-week blood test is to look for red cell antibodies in maternal blood, especially anti-D. For women whose blood group is Rh-D negative and who don't have preformed antibodies, 28 weeks is a standard time to offer passive anti-D to prevent red cell immunisation.

So these are the standard 28-week tests in Australia. The next generic tasks are checking on maternal psychosocial wellbeing and health education needs. For women with uncomplicated pregnancies in Australia, mostly they expect a few non-milestone visits next, for example, 31 and 34 weeks, before the next milestone visit at 36 weeks.

In lower resource settings using a FANC approach, the four essential visits are targeted at 16, 26, 32, and 36-week gestation. But look out for podcasts about the Australian milestone visits at 36 and 41 weeks and a podcast about the in-between non-milestone visits. And I hope you enjoy your clinical placement in women's and newborn health.