Obstetrics and Gynaecology
Preconception Care and Diagnosis of Pregnancy
Preconception counselling, folic acid, teratogen review and diagnosis of pregnancy with beta-hCG and ultrasound for MBBS, mapped to NMC codes OG5 and OG6.
MedNext Academy | 3 min read
Preconception Care and Diagnosis of Pregnancy
Preconception counselling, folic acid, teratogen review and diagnosis of pregnancy with beta-hCG and ultrasound for MBBS, mapped to NMC codes OG5 and OG6.
This chapter covers the care that ideally begins before pregnancy and the clinical and laboratory diagnosis of pregnancy once it starts. It explains folic acid supplementation, drug and disease optimisation for high-risk women, the presumptive, probable and positive signs of pregnancy, and the use of beta-hCG and ultrasound for confirmation and dating.
High-yield: Preconception Care and Diagnosis of Pregnancy
- Folic acid 400 micrograms daily is started before conception and continued through the first trimester to prevent neural tube defects.
- Women with a previous neural tube defect or on antiepileptics take high-dose folic acid 4 to 5 milligrams daily.
- Preconception control of diabetes and optimisation of thyroid status reduce the risk of congenital anomalies and miscarriage.
- Rubella and hepatitis B status should be checked before pregnancy so that vaccination can be given while not pregnant.
- Teratogenic drugs such as warfarin, isotretinoin, valproate and ACE inhibitors should be switched to safer alternatives before conception.
- The most reliable early confirmation of pregnancy is a urine test detecting beta-hCG, positive from about the time of the missed period.
- Amenorrhoea, nausea and breast changes are presumptive symptoms, not proof, of pregnancy.
- Probable signs include Hegar's sign (softening of the isthmus), Goodell's sign (cervical softening) and Chadwick's sign (bluish vaginal discolouration).
- Positive signs of pregnancy are foetal heart activity, foetal movements felt by the examiner and visualisation of the foetus on ultrasound.
- Transvaginal ultrasound shows a gestational sac from about 4.5 to 5 weeks and foetal cardiac activity from about 6 weeks.
- Naegele's rule estimates the expected date of delivery by adding 9 months and 7 days to the first day of the last menstrual period.
- The last menstrual period dating assumes a regular 28-day cycle; a first-trimester crown-rump length scan is the most accurate dating method.
- A quantitative beta-hCG that fails to rise appropriately raises concern for ectopic pregnancy or early pregnancy failure.
- High-risk women benefit from preconception counselling on optimising chronic disease, medication review and lifestyle before conceiving.
Diagnosing and dating pregnancy
- **Best early confirmation:** Urine or serum beta-hCG, positive around the missed period.
- **Positive signs:** Foetal heart activity, examiner-felt movements, ultrasound visualisation of the foetus.
- **Most accurate dating:** First-trimester crown-rump length on ultrasound.
- **Preconception folic acid:** 400 micrograms daily; 4 to 5 milligrams if prior neural tube defect or on antiepileptics.
NMC competencies in this chapter
- **OG5.1:** Preconception counselling for a healthy pregnancy
- **OG5.2:** Preconception care for women at high risk of pregnancy complications
- **OG6.1:** Diagnosis of pregnancy, pregnancy tests and gestational age assessment
Frequently Asked Questions
How much folic acid is advised before pregnancy?
Most women take 400 micrograms daily starting before conception. Those with a previous neural tube defect or on antiepileptics need a higher dose of 4 to 5 milligrams daily.
What are the positive signs of pregnancy?
Foetal heart activity, foetal movements felt by the examiner and ultrasound visualisation of the foetus. These are definitive, unlike presumptive symptoms such as nausea.
What is the most accurate way to date a pregnancy?
A first-trimester ultrasound measuring crown-rump length. Dating from the last menstrual period assumes a regular cycle and is less reliable.
Why does preconception care matter for exams and practice?
Optimising diabetes, thyroid status and teratogenic drugs before conception measurably reduces anomalies and miscarriage, a favourite counselling theme in vivas and single-best-answer questions.
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