Vision Changes in Pregnancy

Today we are joined by Dr. Ben Young. Ben is an ophthalmology resident at Yale New Haven Hospital in Connecticut, and is sharing with us a common complaint that we know very little about - the eye in pregnancy!

Ben also hosts Eyes For Ears, an educational podcast and flashcard reference for ophthalmology residents. If you happen to know any vision sciences students or residents, let them know about it!

We start out talking about the “ocular vital signs,” which are:
- Visual Acuity
- Pupils (“swinging light test”)
- Intraocular pressure
- Visual Fields
- Extra-ocular movements

Image copyright of FOAMCast

The most common reasons for ophthalmology issues in pregnancy relate to either 1) vision changes requiring a new prescription, or 2) dry eye. However, don’t forget some key pearls:

- Monocular (single eye) double vision — dry eye. Binocular (both eye) double vision — badness!
- A Snellen chart and a flashlight are the best tools you have to help out a consultant.
- Check out this video on how to perform a swinging flashlight test.

Further reading from the OBG Project:
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Is Cataract Surgery in Women Associated with Decreased Mortality?

Fetal Growth Restriction

On today’s episode, we tackle the new ACOG PB 204 on fetal growth restriction. There’s quite a bit to cover, so you’ll see today’s episode is a bit longer. We’ve enlisted the help of Chris Nau, MD, an MFM fellow at Brown, to help us through all the recommendations.

FGR, as Chris explains, results from a process where there is mismatch between fetal demands and placental supply of oxygen and nutrients. Symmetric growth restriction arises earlier, and asymmetric growth restriction arises later, with the differentiating factor being asymmetric growth restriction resulting in a larger head circumference : abdominal circumference ratio. The PB 204 goes into many of the common causes, but the list is long!

ACOG PB 204

ACOG and SMFM state that a sonographic estimated fetal weight less than the 10th percentile is the measurement definition of fetal growth restriction, though as Chris explains, there are a number of limitations to this definition.

Screening is performed using a fundal height at prenatal visits, and if the height is < 2cm discrepant from the gestational age, an ultrasound should be performed. Alternatively ultrasounds can be used primarily, especially with known maternal conditions that might predispose someone to FGR, or if fundal height assessments are difficult.

Once a growth-restricted infant is identified, you should check the due date calculation and make sure it is right! (Check out our previous episode on dating!) Next, re-review the mother’s medical history and pregnancy history, including aneuploidy screening, to date. A level 2 ultrasound may help identify anatomic abnormalities that point to an etiology. And identifying modifiable risk factors, including optimizing medical conditions or smoking cessation, may be worthwhile.

With respect to management, there are variable institutional protocols with respect to monitoring. Umbilical artery velocimetry reduces risk of perinatal death when added to other antenatal testing (i.e., modified BPP). Normal or elevated systolic : diastolic flow ratio does not carry increased risk to the fetus; however absent or reversed end-diastolic flow increases risk for perinatal mortality. Chris reviews our protocol at Brown in the podcast.

Timing of delivery is a tricky one — there is not great evidence, and the newest guidance from PB 204 states that reassuring fetal testing should deliver between 38w0d - 39w6d. If there is FGR plus concerning maternal or fetal findings, delivery should be considered between 32w0d to 37w6d.

When counseling about future pregnancies, there is about a 20% risk of recurrence. At this time, ACOG/SMFM do not recommend baby aspirin for prevention of FGR in the absence of other risk factors for preeclampsia.

Further reading from the OBGProject:
Fetal Growth Restriction: Diagnosis, Evaluation, and Management
Aspirin Treatment - ACOG and USPSTF Recommendations

Interpreting Cardiotocography/EFM Part I: Definitions

Today we take a break from STIs to jump back into obstetrics, and are joined by two very special guests: Liz Kettyle and Linda Steinhardt, both of whom are certified nurse midwives (CNMs) and clinical educators at the Warren Alpert Brown School of Medicine.

ACOG PB 106 (membership required) forms the basis for this episode and in a future episode, we will discuss management of cardiotocography (CTG). Also, for a recent article surrounding the naming of CTG vs. EFM vs. all the other names for this technology, check out a recent AJOG article on its now 50-year history.

We also are using some special sound effects for these episodes! As you listen to the various sounds for different types of decelerations, keep in mind that the higher-pitched sound represents a contraction pattern, and the lower-pitched sound represents the fetal heart rate response.