Pregnancy has historically been dated from the last menstrual period (LMP) with a duration of 40 weeks to give an estimated date of delivery (EDD) as a specific date. In fact term is usually a range from 37 – 42 weeks and these days pregnancy dates are usually set by ultrasound measurement.
The American College of Obstetricians and Gynecologists, the American Institute of Ultrasound in Medicine, and the Society for Maternal-Fetal Medicine recommend that –
Ultrasound measurement of the embryo or fetus in the first trimester (up to and including 13 6/7 weeks of gestation) is the most accurate method to establish or confirm gestational age.
A new formula for estimating gestational age based on ultrasound examination was reported in – Obstet Gynecol. 2017;130:433-441
Medical assessment prior to becoming pregnant. The Centers for Disease Control and Prevention (CDC) has defined preconception care as “a set of interventions that aim to identify and modify medical, behavioral, and social risks to a woman’s health or pregnancy outcome through prevention and management.”
Pre-conception care includes –
1. Optimizing the management of chronic maternal health problems.
2. Providing lifestyle advice to avoid behaviours hazardous to a pregnancy, such as smoking, drinking excessive alcohol, or taking drugs.
3. Providing advice to optimize the health of the mother and baby, such as guidance on taking folic acid supplements.
4. Identifying couples who are at increased risk of having a baby with a genetic or chromosomal malformation, and providing them with sufficient knowledge to make informed decisions.
A number of factors have to be considered early in pregnancy, if not addressed at the pre-pregnancy stage.
Pre-existing medical conditions in the individual, such as diabetes, renal disease, hypertension, HIV, previous thrombosis and epilepsy, would have to be considered in managing the pregnancy. Congenital abnormalities and genetic problems have to be considered in both parents.
Obesity – a BMI of over 30 carries an increased risk of complications such as hypertension, diabetes, and caesarean delivery also attainment of a normal pre-conception BMI will also likely prevent obesity and related long-term health effects in the developing child.
Antenatal screening is offered for –
• Foetal anomalies by ultrasound
• Down’s syndrome
• Rubella status
• Hepatitis B
• Tay-Sachs disease in high risk individuals
Blood volume increases during pregnancy, beginning at 6-8 weeks gestation, which accounts for part of the weight gain. The increase is mainly in the plasma rather than the cellular constituents of the blood leading to a fall in haemoglobin and the possible need for iron.
As the uterus grows pushing up the diaphragm there may be some breathlessness, light headedness and possible fainting. Palpitations and irregular heartbeats are also not uncommon in pregnancy.
Nutrition in Pregnancy
During early pregnancy, most women experience an increased appetite, with extra caloric needs of approximately 300 kcal/d. Some women have nonfood cravings, known as pica.
Should certain foods be avoided during pregnancy?
Pregnant women are at increased risk of bacterial food poisoning. For the safety of both mother and fetus, it is important to take steps to prevent foodborne illnesses, including the following
• Properly cook food to kill bacteria.
• Cook eggs until they have a firm yolk and are white. Eggnog and hollandaise sauce have raw or partially cooked eggs and are not considered safe.
• Eat liver in moderation. Liver can contain extremely high levels of vitamin A.
• Avoid products containing unpasteurized milk, including soft cheeses like brie, feta, and blue cheese. Also avoid unpasteurized juice.
• Carefully wash all fruits and vegetables to eliminate harmful bacteria.
• Longer-lived and larger fish, such as shark, swordfish, king mackerel, and tilefish, have increased mercury levels and the FDA advises that they should not be eaten by pregnant or nursing women.