BMI is weight in kilograms divided by the square of the height in metres.
There is now much data that shows that the following risks are increased if the BMI is >= 25:
Pre-pregnancy
1. Reduced fertility - There are multiple mechanisms that reduce fertility rates in women when the BMI is increased:
Polycystic ovarian syndrome (PCOS) with reduced ovulation
Poorer egg quality
Reduced receptivity of the endometrium
Others
2. Higher chance of already having pre-existing diseases like high blood pressure, diabetes mellitus which could further increase the risk of complications during pregnancy.
During pregnancy
1. Miscarriages
2. Fetal anomalies (e.g. neural tube defects, cleft lip / palate, hydrocephalus, limb reduction, cardiac defects) - the ultrasound images are also less clear when the ultrasound scan is performed on a woman with increased BMI compared to a woman with normal BMI.
3. Preterm birth
4. Large baby at birth - this increases the risk of difficult vaginal delivery.
5. Stillbirth
6. Higher risks of medical problems during pregnancy e.g. gestational diabetes mellitus, gestational hypertension, pre-eclampsia, anxiety, depression, venous thromboembolism.
Delivery
1. Labour problems (e.g. longer labour, shoulder dystocia, Caesarean section, higher need for induction of labour, higher failure rates for induction of labour, and wound infections)
2. Caesarean section - Caesarean section rates are higher than women with low BMI
After delivery
1. Wound infections
2. Neonatal problems - low blood sugar levels, respiratory distress. These issues may require usually short admissions to the ICU for monitoring and treatment.
What to do?
It is known that the risks of pregnancy increases with maternal age. It is also known that higher BMI increases the risk of pregnancy, and that reduction in weight reduces at least some of these risks.
Therefore, one is overweight or obese and is young, one may allow up to 1 year to give one's best efforts to lose weight before conception. If one is more than or equal to 35 years old, one may still allow a shorter period (e.g. 3-6 months) to give one's best efforts to lose weight before conception.
Weight loss interventions
1. Dietary restriction of carbohydrates and / or intermittent fasting are effective weight loss programs that require support from family members and close ones for better success. It also requires perseverance and discipline.
2. Regular physical exercise
3. Medications such as oral phentermine or liraglutide injections (recent data shows good efficacy) may be necessary to reduce weight especially if a sustained effort at diet and regular physical exercise fails to achieve optimal weight loss. This is especially so if the BMI is still >=30.
4. Meal replacement products - there are various meal replacement products available in the market that are of low calories and with adequate nutrition to replace some of our traditional meals.
5. Surgery to reduce the size of the stomach - this may be indicated if the BMI is >= 35 especially if there are pre-existing medical problems such as diabetes mellitus.