Obese women have a higher prevalence of amenorrhorea and infertility. Obesity is common, occurring in 35–40% of women with polycystic ovary syndrome.64 Fifty percent of overweight women have polycystic ovaries or polycystic ovary syndrome compared with 30% of lean women.65 The risk of miscarriage before the first liveborn child is 25–37% higher in obese women.66 Obesity has a negative impact on infertility treatment and if conception occurs, there is an increased risk of pregnancy loss. Three cohort studies have suggested that obesity is an independent risk factor for spontaneous miscarriage in women who undergo fertility treatment.67–69 With ovulation induction using gonadotrophin-releasing hormone, there is a three-fold increase in the risk of pregnancy resulting in miscarriage, and with egg donation in women with a BMI greater than 30 kg/m2, there is a four-fold increased risk of miscarriage. Therefore, obese women should be encouraged to lose weight prior to their fertility treatment as this can result in significant improvement in reproductive outcome for all fertility treatment.70
Delivery and surgical complications
The inability to obtain interpretable external fetal heart rate and uterine contraction patterns in obese women is frequent. Women with a BMI of 35 kg/m2 or greater are likely to have pre-existing medical conditions such as hypertension or diabetes, and this may further increase their anaesthetic risks. Specific resources such as additional blood products, a large operating table and extra personnel in the delivery room are essential prior to the delivery. Other intrapartum complications include failure of epidural insertion, increased risk of aspiration during anaesthesia, difficult intubation, poor peripheral access and difficulty in monitoring of maternal blood pressures. Increased retention of lipid-soluble agents, increased drug distribution and more rapid desaturation have also been reported.71 The significant difficulty in administering epidural analgesia should not preclude their use in labour. Prophylactic placement of an epidural catheter when not contraindicated in labouring morbidly obese women would potentially decrease anaesthetic and perinatal complications associated with attempts at emergency provision of regional or general anaesthesia.72
Obese women had a higher rate of induction of labour (25.5%, BMI 20–30 kg/m2; 36%, BMI > 30 kg/m2; OR 1.6, 95% CI 1.3–1.9)73 and a higher rate of failed induction (7.9 versus 10.3 versus 14.6% with increasing BMI)34 and caesarean section rates in nulliparous women (20.7% in the control group versus 33.8% in obese group and 47.4% in morbidly obese group; P > 0.01).33 There was also a higher rate of obstetric complications in women who were overweight at their first antenatal visit such as operative vaginal delivery (8.4 versus 11.4 and 17.3% with increasing BMI; P < 0.001), shoulder dystocia (1 versus 1.8 and 1.9% with increasing BMI; P < 0.021) and third/fourth degree lacerations (26.3 versus 27.5 and 30.8% with increasing BMI; P < 0.001) when compared with the normal BMI group.34 The frequency of both elective (8.5 versus 4%) and emergency caesarean section (13.4 versus 7.8%) were almost twice as high for the very obese women compared with the normal BMI group.2 Maternal obesity was found to influence the route of delivery, independent of co-morbid conditions such as macrosomia, nulliparity, induction or diabetes, and obese and overweight women had a higher risk of caesarean section delivery compared with normal weight women (13.8 and 10.4 versus 7.7%, P < 0.0001).74 In another study of 126 080 deliveries, after excluding women with diabetes and hypertensive disease, there was a three-fold increased risk in failure to progress in the first stage and higher caesarean section rate of 27.8 versus 10.8% (OR 3.2) in the obese group compared with the normal weight group.75 The increase in emergency caesarean sections in these obese women may be related to an increased number of large-for-gestational-age infants, suboptimal uterine contractions and increased fat disposition in the soft tissues of the pelvis leading to dystocia during labour.
Common operative complications include the loss of landmarks, making vascular access difficult. A hospital-based perinatal database was used to identify women with a BMI of greater than 35 undergoing their first caesarean delivery. These authors reported an overall wound complication rate of 12.1%; those with a vertical skin incision were at greatest risk (34.6 versus 9.4%).76 The proposed benefits of a transverse incision are reported to have a more secure closure, less fat dissection and less postoperative pain. Earlier ambulation and deep breathing can further decrease the risk of atelectasis and hypoxaemia. The disadvantage of a low transverse incision is that it potentially increases infection rates due to the warm and moist area underneath the pannus. Retraction of the large pannus, in order to gain good access, can compromise the maternal cardiopulmonary system.71 A vertical skin incision allows a better visualisation of the operative field with less physical exertion on the operator, decreased operative time and decreased blood loss. However, it should be closed by a mass closure technique with either a permanent or delayed absorbable monofilament suture.
In a randomised study (n= 76), the use of a subcutaneous drain or suture closure was assessed as an effective means of decreasing wound complications. These authors concluded that a subcutaneous suture or drainage in women with at least 2 cm of subcutaneous fat at the time of caesarean delivery can reduce the incidence of postoperative wound complications.77
Postoperative respiratory complications such as pneumonitis are more common. Early mobilisation, aggressive chest physiotherapy and adequate pain control are essential components of effective postoperative care.72,78
In the puerperium, endometritis, postpartum haemorrhage, prolonged hospitalisation and wound infections appear more frequent in obese women (Table 2). The risk of postpartum haemorrhage rises with increasing BMI and is about 30% more frequent for women with moderately raised BMI and about 70% more frequent for women with highly raised BMI compared with the normal BMI group.2
Table 2. Maternal complications according to each BMI category
| ||BMI (kg/m2) group||Proportion (%)||OR (99% CI)|
|Chest infection||20–25||0.13|| |
|Genital infection||20–25||0.66|| |
|Wound infection||20–25||0.39|| |
|Urinary tract infection||20–25||0.69|| |
|Pyrexia of unknown origin||20–25||1.00|| |
|Prolonged postnatal stay||20–25||20.35|| |