Pregnancy Timeline

There are several key definitions to become familiar with:

  • Last menstrual period (LMP) refers to the date of the first day of the most recent menstrual period
  • Gestational age (GA) refers to the duration of the pregnancy starting from the date of the last menstrual period
  • Estimated date of delivery (EDD) refers to the estimated date of delivery (40 weeks gestation)
  • Gravida (G) is the total number of pregnancies a woman has had
  • Primigravida refers to a patient that is pregnant for the first time
  • Multigravida refers to a patient that is pregnant for at least the second time
  • Para (P) refers to the number of times the woman has given birth after 24 weeks gestation, regardless of whether the fetus was alive or stillborn
  • Nulliparous (“nullip”) refers to a patient that has never given birth after 24 weeks gestation
  • Primiparous technically refers to a patient that has given birth after 24 weeks gestation once before (see below)
  • Multiparous (“multip”) refers to a patient that has given birth after 24 weeks gestation two or more times

TOM TIP: The term primiparous, or “primip” is a bit confusing. Technically, it refers to a woman that has given birth once before. However, it is often used on the labour ward to refer to a woman that is due to give birth for the first time (and has never given birth before). You may hear patients referred to on the labour ward as a “primip” when they have never given birth before.

 

The timeline for each pregnancy depends on the start date of the last menstrual period (LMP). This determines the gestational age (GA) and the estimated date of delivery (EDD) of the pregnancy. After the booking scan, the gestational age is more accurately assessed and the estimated date of delivery is updated accordingly.

The gestational age is described in weeks and days. For example:

  • 5 + 0 refers to 5 weeks gestational age (since the LMP)
  • 13 + 6 refers to 13 weeks and 6 days gestational age

 

Gravidity and Parity

It is worth becoming familiar with gravida and para, as you will find this written on medical records. Here are some examples:

  • A pregnant woman with three previous deliveries at term: G4 P3
  • A non-pregnant woman with a previous birth of healthy twins: G1 P1
  • A non-pregnant woman with a previous miscarriage: G1 P0 + 1
  • A non-pregnant woman with a previous stillbirth (after 24 weeks gestation): G1 P1

 

Trimesters

The first trimester is from the start of pregnancy until 12 weeks gestation.

The second trimester is from 13 weeks until 26 weeks gestation.

The third trimester is from 27 weeks gestation until birth.

It is worth noting that fetal movements start from around 20 weeks gestation, and continue until birth.

 

Key Milestones

Dates

Event

Purpose

Before 10 weeks

Booking clinic

Offer a baseline assessment and plan the pregnancy

Between 10 and 13 + 6

Dating scan

An accurate gestational age is calculated from the crown rump length (CRL), and multiple pregnancies are identified

16 weeks

Antenatal appointment

Discuss results and plan future appointments

Between 18 and 20 + 6

Anomaly scan

An ultrasound to identify any anomalies, such as heart conditions

25, 28, 31, 34, 36, 38, 40, 41 and 42 weeks

Antenatal appointments

Monitor the pregnancy and discuss future plans

 

Additional Milestones

There may be additional appointments necessary if the woman fits certain criteria:

  • Additional appointments for higher risk or complicated pregnancies
  • Oral glucose tolerance test in women at risk of gestational diabetes (between 24 – 28 weeks)
  • Anti-D injections in rhesus negative women (at 28 and 34 weeks)
  • Ultrasound scan at 32 weeks for women with placenta praevia on the anomaly scan
  • Serial growth scans are offered to women at increased risk of fetal growth restriction

 

Routine Antenatal Appointments

Several things are covered at each routine antenatal appointment:

  • Discuss plans for the remainder of the pregnancy and delivery
  • Symphysis–fundal height measurement from 24 weeks onwards
  • Fetal presentation assessment from 36 weeks onwards
  • Urine dipstick for protein for pre-eclampsia
  • Blood pressure for pre-eclampsia
  • Urine for microscopy and culture for asymptomatic bacteriuria

 

Vaccines

There are two vaccines offered to all pregnant women:

  • Whooping cough (pertussis) from 16 weeks gestation
  • Influenza (flu) when available in autumn or winter

 

Live vaccines, such as the MMR vaccine, are avoided in pregnancy.

 

Last updated August 2020
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