A0. Good-to-know stuff which isn’t covered in other topics

Page created on December 20, 2021. Last updated on December 23, 2021 at 10:06

This topic includes some stuff which I think is important to know, but which don’t fit under any specific topic. I will add to this topic as I go about writing the other topics.

Obstetric notation

During obstetric history taking, it’s important to ask the number of pregnancies and deliveries thus far, as well as the mode of delivery. Not all pregnancies end in a delivery, and so the two numbers are often different and summarised in a short-hand notation. The number of pregnancies in total is noted after a letter G (gravida), and the number of deliveries is noted after a letter P (para). Any current pregnancy is not counted. Here are some examples:

  • 5 pregnancies in total, 3 deliveries: G5 P3
  • 1 pregnancy in total, 1 delivery: G1 P1

Verbally, one would say “gravida 1 para 1”, for example.

Sometimes, this notation is shortened. A G0 implies P0, and so rather than G0 P0 we’d often write simply G0. If all pregnancies have ended in delivery, we can omit the “gravida” part, which implies that the number of pregnancies and deliveries is equal. As such, writing only P3 implies G3 P3.

Gestational age

Because it’s impossible to routinely know the exact date at which the conception occurred, gestational age and due date is calculated based on how many weeks and days have passed from the first day of the last menstrual period (LMP) the mother experienced. This day is considered day 0. The gestational age is then stated weeks and days following this date. The day after is then week 0 day 1, followed by week 0 day 2, and so on until week 0 day 6, which is followed by week 1 day 0. As such, week 1 day 0 is the 7th day after the first day of the last menstrual period.

Gestational age of week X day Y is usually written like this: X/Y or X+Y. Examples:

  • Week 5 day 3 is written as 5/3 or 5+3
  • Week 36 day 6 is written as 36/6 or 36+6

Prenatal care

Prenatal care refers to the care pregnant women get during pregnancy. This care is important to screen for problems, teach about good and bad behaviour and warning signs, and referring the patient to a specialist (obstetrician) if necessary.

Pregnant women may attend prenatal care at a midwife or a general practitioner, depending on preference and availability. When a woman is diagnosed with pregnancy (a positive pregnancy test), she should make contact with the midwife or GP to organise regular prenatal care visits.

The care provider, whether a midwife or GP, should refer the patient to an obstetrician if there are any signs of abnormality or high risk.

The frequency of prenatal care visits, as well as which examinations are performed at these visits, vary from country to country. During prenatal care, the following examinations and tests are often performed:

  • Complete blood count
  • Screening for certain infectious diseases (hepatitis, HIV, syphilis)
  • Screening for hypertensive disorders of pregnancy (maternal BP, urine protein content)
  • Screening for Rh incompatibility (blood typing, Rh determination)
  • Screening for bacteriuria (urine culture)
  • Symphysis fundal height – the length from the top of the uterus to the top of the pubic symphysis
    • Both of these landmarks can be palpated
    • This length grows more or less constantly from week 20 and onwards (~1 cm/week)
    • Used to assess foetal growth and development
  • Listen to foetal heartbeat
  • Screening for diabetes (blood glucose, oral glucose tolerance test) – see topic B18
  • Assessing foetal lie – see topic B4

For Norwegians, the recommended contents of prenatal care visits can be found here and here.

In Hungary, the schedule of prenatal care visits is as follows:

  • Every four weeks up to 28 weeks gestation
  • Every two weeks from 28 – 36 weeks gestation
  • Every week from 36 weeks gestation to delivery

Extra or more frequent visits may be indicated in case of high risk pregnancies.

During early prenatal care visits, a due date is estimated based on the last menstrual period (see Naegele’s rule below). However, during first and second trimester ultrasounds the due date is re-estimated based on the measurements of foetal biometry (see topic B8).

Naegele’s rule

Naegele’s rule can be used to estimate the due date from the first day of the last menstrual period. The due date is calculated like this:

Due date = first day of last menstrual period + 7 days + 1 year – 3 months

Instead of calculating + 1 year – 3 months you could also just add 9 months, which is more intuitive in my opinion. This rule works because 9 months is approximately 273 days, and a full pregnancy is normally 280 days since the first day of the last menstrual period.

Here are a couple of examples:

  • First day of last menstrual period was December 16th -> due date September 23rd
  • First day of last menstrual period was May 29th -> due date March 5th

Foetal movements

The pregnant women should feel foetal movements from approximately week 16. A pregnant woman’s subjective perception that the foetus is moving less than normally should be taken seriously. Most cases turn out to be false alarms, but a woman’s subjective perception of less movement may be an early warning sign of abnormality.

Detection of foetal heart action by ultrasound and/or CTG should be performed. In case of normal findings, the woman can usually go home.

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Next page:
A1. Stages of labour

Parent page:
Obstetrics and gynaecology 1

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