How obesity affects fertility and pregnancy | 3 min read

Obesity has a profound effect on a woman’s fertility, both natural and assisted.  Not only does it impact on the chances of conceiving, it also impacts on the risks of maternal and foetal complications during the pregnancy and delivery process.  There are also peri- and post-natal implications for mother and baby.

Obesity is associated with an increased risk of foetal complications in the antenatal period including:

  • Congenital malformations (neural tube defects, cleft lip / palate and cardiac abnormalities)
  • Miscarriage
  • Macrosomia
  • Intrauterine death
  • Intrauterine growth restriction

Obesity is linked with increased maternal complications during the antenatal period including:

  • Ectopic pregnancy
  • Thrombo-embolic disease
  • Gestational diabetes
  • Pregnancy induced hypertension
  • Pre-eclampsia

Obesity is linked with increased complications during labour and delivery including:

  • Shoulder dystocia
  • Induction of labour
  • Operative intervention rated (emergency caesarian section and vaginal tears)

Obesity is linked with increased maternal and foetal complications in the perinatal period including:

  • Postpartum haemorrhage
  • Postpartum infection
  • Longer hospital stays
  • Increased requirement for neonatal intensive care
  • Low Apgar scores at 5 minutes and foetal distress
  • Still birth
  • Maternal mortality

Obesity is lined with an increased maternal risk in the postnatal period of:

  • Impaired glucose tolerance
  • Type 2 diabetes mellitus
  • Cardiovascular disease
  • Hypertension

Maternal obesity is associated with the following findings in childhood:

  • Reduced breast feeding
  • Increased overfeeding
  • Increased exposure to a high calorie diet after weaning
  • Increased risk of developing childhood obesity
  • Increased risk of cardio-metabolic complications in adult life

Losing excess weight reduces the maternal risks of developing complications in the antenatal period, during delivery and postpartum. The risks of complications to the unborn baby are also significantly reduced and complications related to the birth and postnatally are also much lower. Educate overweight and obese women to try and achieve as normal a BMI as possible pre-conceptually and take the recommended dose of folic acid during pregnancy. To keep to a normal weight gain during pregnancy and to lose as much excess weight as possible after pregnancy would reduce the associated health risks for both mother and baby in the short and longer terms.

According to the findings of the Confidential Enquiry into Maternal and Child Health, in approximately 5% of pregnancies maternal BMI is >35kg/m2 and in 2% of pregnancies, maternal BMI is >40kg/m2.  Very few obstetric units provided obesity-specific information and pre-pregnancy care to obese women. The complications associated with obesity in pregnancy such as miscarriage and neural tube defects often occur in the first trimester and before women are seen in the antenatal clinic. 

This highlights the need for improved pre-pregnancy counselling and education for these women by healthcare providers present in areas such as general practice and family planning clinics the report discovered that only a small proportion of the cohort of obese women studied were taking folic acid pre-conceptually and the vast majority of these were not taking the higher dose recommended.  And this is in spite of the known relationship between obesity being linked to higher rates of neural tube defect.  It also found that for each unit increase in induction of labour, caesarean section delivery and primary postpartum haemorrhage.

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