Normal obstetrics scan (third trimester singleton)

Case contributed by Dennis Odhiambo Agolah

Presentation

History of repaired congenital cardiopathy, Tetraology of Fallot (TOF) in a female aged 30 years, para 1+0, currently gravid at thirty six plus weeks gestation. For routine fetal surveillance.

Patient Data

Age: 30 Years
Gender: Female

A single viable intrauterine pregnancy in cephalic presentation. Fetal cardiac and somatic activities are present. FHR =154 BPM and regular. No gross fetal skull, spine, chest, abdomen or limb anomalies. The fetal ventrices, nasal bone, lips, 4-chamber heart, stomach and bladder bubbles, kidneys, cord insert and the 3-vessel cord grossly look normal. The amniotic liquor is normal for gestation (greatest pocket measures 7.74 cm in depth). The placenta is anterior, not low lying and is intact. It measures 2.59 cm in thickness with homogeneous echogenicity and with features consistent with grade II pattern maturity. The cervix is closed and measures 3.74 cm in length.

Biometric Score Biophysical Profile score

BPD = 35w 2d Fetal breathing = 2/2

HC = 38w 0d. Fetal movements = 2/2

AC = 36w 5d. Fetal tone = 2/2

FL = 35w 3d. AFI = 2/2

Total = 8/8.

Composite gestational maturity by ultrasound corresponds to 36 weeks 6 days gestation. EDD = day/month/year. EFW = 2913 grams. The umbilical arterial resistive index of 0.50 and the right middle cerebral arterial resistive index of 0.78 noted are within normal limits. Cerebral -placental ratio = 1.56 (normal). Bilateral maternal uterine arterial Doppler waveforms and indices is unremarkable with normal pulsatility and resistive values (Rt UtA PI = 1.11; RI = 0.62. Lt UtA PI =0.71, RI = 0.47).

Fetal ductus venosus evaluation shows normal S-D-a waveform and normal velocities/indices with a mean PI 0.63 of and a mean RI of 0.51.

CONCLUSION

  • Viable singleton intrauterine pregnancy at 36 weeks 6 days gestation with the fetus currently in cephalic presentation; LOP position.

  • No nuchal cord.

Case Discussion

Normal singleton third trimester obstetrics ultrasound scan for reference.

Areas to highlight during routine obstetrics ultrasound:

Quick general surveying:

  • sweeping the transducer over the maternal abdomen under a generously spread ultrasound gel, to verify the/a pregnancy, site, multiplicity and viability.

Printable/writable documentation:

  • myocardial fetal activity,

  • maternal cervical length, and status of the internal and the external ostia.

  • fetal orientation in utero; Fetal presentation, or fetal lie, fetal attitude and/or fetal position is documented.

  • placental location, placental thickness, placental maturity (based on the weeks per gestation) and parenchymal status.

  • amniotic fluid index/status (AFI), whether increased, reduced, or normal for gestation.

  • gross fetal morphology; gross fetal systems i.e central nervous system, cardiovascular system, external genitalia (reproductive system), musculoskeletal system, genitourinary tract system, gastrointestinal tract system. Also, the umbilical cord, cord inserts and 3-vessel cord status.

  • biometrics; If mid to late trimesters; BPD, HC, AC, FL and/or any other parameters as the institution allows/recommend. EFW, and expected due date (EDD) also documented.

  • Doppler velocimetry; Basically from 30 weeks gestation and above, routinely umbilical artery and right middle cerebral artery resistive indices is included. However, the values can be quantified before 30 weeks gestation as need arises. Where maternal pre-eclampsia is confirmed or suspected, bilateral maternal uterine arteries pulsatility and resistive indices are routinely documented. Also, where fetal cardiac anomalies are suspected/confirmed ductus venosus waveform and atrial wave is keenly assessed/documented.

  • fetal umbilical cord entanglements; presence or absence of nuchal cord, around the limbs or abdomen or chest, number of turns/twists, tightness or loose, is documented.

  • any other coexisting maternal anomalies e.g. fibroids, ovarian cysts etc is to be documented.

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