Background
Up to 21.1% of women in Austria aged 30 to 45 years are overweight (BMI 25 – 29.9 kg/m2) and 9.1% obese (BMI ≥ 30 kg/m2) [1]. Decreased fertility and complications of pregnancy such as diabetes, hypertension,
pre-eclampsia and neonatal macrosomia are frequently reported in this population [2], [3].
Weight loss achieved by a change in lifestyle, drug therapy or bariatric surgery is
associated with improved fertility and reduced rates of complications during pregnancy
[4], [5].
Bariatric surgery is the most effective method for achieving weight loss [6]. Bariatric surgery is indicated above a BMI of ≥ 40 kg/m2 or at a BMI of 35 – 40 kg/m2 with associated comorbidities (possibly even at a BMI of > 30 to < 35 kg/m2 in case of type 2 diabetes). The procedure may entail a restrictive or malabsorptive
technique, or a combination of the two [7], [8].
Bariatric surgery is being offered increasingly to patients of childbearing age. It
is therefore necessary to be aware of its effects on pregnancy and childbirth. In
addition to the potential positive effects on cardiovascular [9] and metabolic parameters [10], potential adverse effects such as maternal anaemia [11], an increased risk of intra-abdominal hernias [12], impaired glucose metabolism [13] and a higher risk of foetal growth restriction [14] must be afforded closer attention.
Methods
The references for this consensus statement were extracted from the PubMed and MEDLINE
databases using the following MeSH keywords: “obesity”, “bariatric surgery”, “pregnancy
and bariatric surgery”, “obesity and fertility”, “obesity and pharmacology”, “obesity
and bariatric surgery”, “obesity and diabetes”, “diabetes and pregnancy”, “gestational
diabetes and hypertension”, “obesity and hypertension”, “bariatric surgery and hypertension”,
“obesity and heart disease”, “bariatric surgery and heart disease”, “gastric bypass
and anemia”, “gastric bypass and hyperparathyroidism”, “bariatric surgery and vitamin
D”, “dietary supplements and gastric bypass”, “gastric bypass and abdominal hernia”,
“fetal macrosomia”, “infant, small for gestational age”, “breastfeeding and bariatric
surgery”. Longitudinal studies such as cohort studies and systematic reviews (including
meta-analyses) were given preference in the compilation of this consensus statement.
In addition, the guidelines of the American College of Obstetricians and Gynaecologists
(ACOG) on the care of patients during pregnancy and delivery after bariatric surgery
were taken as a reference.
Preconceptional Aspects
Obesity is often associated with hyperandrogenaemia and polycystic ovary syndrome
(PCOS). Follicle growth and oocyte maturation are impaired by the compensatory hyperinsulinaemia
and often increased insulin resistance secondary to PCOS, resulting in reduced fertility
[15], [16]. Hence, even young women who are overweight must often rely on assisted reproductive
technologies (ART) to fulfil their desire for a child. Obesity is thus considered
a risk factor for a lower number of eggs and embryos of poorer quality, accompanied
by decreased rates of pregnancy and live birth [17]. Weight loss surgery appears to have a positive effect on hyperandrogenaemia in
most female patients [18], and spontaneous conception has been achieved in up to 58% of infertile women following
surgery [19]. Patients having undergone ART before and after bariatric surgery were found to
have an increased number of eggs, better egg quality, and higher live birth rates
during postoperative treatment cycles [20].
Patients who do not wish to have children must be informed that the efficacy of oral
contraceptives could be reduced as a result of the operation (especially in the case
of malabsorptive procedures) and that parenteral dosage forms or non-hormonal methods
should be considered in the choice of a suitable contraceptive method [21].
Pregnancy after Bariatric Surgery
Glucose metabolism and gestational diabetes
Bariatric surgery reduces the risk of gestational diabetes [11], [22], but malabsorptive procedures in particular can cause fluctuations in blood glucose.
In the 2 h OGTT, for instance, lower fasting glucose concentrations and an excessive
increase in blood glucose were noted 60 min after glucose delivery followed by hyperinsulinaemic
hypoglycaemia after 120 min. Consequently, it can be difficult to diagnose gestational
diabetes as the OGTT does not deliver reliable results [13]. Alternatively, subcutaneous glucose could be measured continuously or capillary
glucose measured repeatedly in the context of a diurnal blood glucose profile [23], [24]. A diurnal blood glucose profile is recommended as of week 24 to 28 of pregnancy
(also earlier, if necessary) [23]. The target values are < 95 mg/dl (fasting) and < 140 mg/dl (1 h postprandial).
No screening test is available as yet for gestational diabetes in pregnancy after
weight-loss surgery. To rule out any pre-existing diabetes mellitus, the HbA1c value (and fasting glucose in addition) should be determined at the first gynaecological
examination [23].
Attention should also be paid in this patient population to the issue of a dumping
syndrome (especially hypoglycaemia after carbohydrate intake). Early dumping syndrome
occurs 15 min to 1 h after a carbohydrate-rich meal and is characterised by transient
arterial hypotension, reflex tachycardia, flush, hyperhidrosis and even syncope [25], [26]. Late dumping syndrome develops two to three hours after a meal and is caused by
excessive insulin secretion with reactive hypoglycaemia and corresponding symptoms
[25], [26]. Standard treatment consists of a modified diet, mainly the avoidance of rapidly
absorbed carbohydrates. Pharmacological interventions are not indicated in pregnancy,
as insufficient data are available [25]. If a dumping syndrome is suspected, dietary advice from a dietologist or specialist
with an additional qualification in nutritional medicine is recommended with a view
to introducing a carbohydrate-modified diet.
Nutrient uptake
Bariatric surgery, especially when malabsorptive procedure is used, influences the
uptake of micronutrients and macronutrients.
Several studies suggest a higher rate of iron deficiency anaemia following bariatric
surgery [5], [27], [28], [29]. Therefore, the iron status should be checked even before conception, if possible,
and closely monitored during pregnancy. The current recommendations for iron replacement
in pregnant women having undergone bariatric surgery range from 40 mg to 600 mg per
day [30], [31], [32]. The iron status should be checked during each trimester of pregnancy as a minimum
[33].
Vitamin B12 deficiency has also been observed in pregnant women who have had bariatric surgery
(5,34). A sublingual dose of 350 µg/day or intramuscular administration of 1000 µg
every 4 – 12 weeks is currently recommended with respect to supplementation [30], [32]. The vitamin B12 status should likewise be monitored in each trimester [33].
Very obese patients are frequently found to have vitamin D3 deficiency; of patients in whom bariatric surgery is planned, up to 84% are affected
[35]. Elevated parathyroid hormone concentrations may also be noted in preoperative patients
due to decreased levels of vitamin D and calcium [35], [36], [37]. Bariatric surgery using a malabsorptive procedure, in particular, appears to intensify
this problem. It has been reported that up to 73.6% of patients develop secondary
hyperparathyroidism five years after surgery despite vitamin D supplementation [36], with long-term effects on bone health [32], [38]. As an adequate maternal calcitriol concentration and the resulting increase in
calcium absorption are important to foetal bone mineralisation, a sufficient supply
of vitamin D3 and calcium is essential in patients who have had bariatric surgery [30]. There is no global consensus on supplementation; current literature describes doses
of 1000 – 2000 mg calcium citrate [30], [31], [32] and 50 – 150 µg or 1000 IU vitamin D3 per day [30], [32], including regular laboratory tests and ultrasound checks for assessing foetal growth
[30], [33], [39].
At present there is no evidence of an increased risk of folic acid deficiency in pregnant
women following bariatric surgery [34], [40], provided this patient population likewise receives supplementation at the standard
recommendation of 400 µg folic acid per day [31], [32], [39]. The folic acid concentrations should still be monitored in each trimester [33], [39].
Other deficiencies observed in pregnant women post bariatric surgery involve vitamins
A and K. There is no general consensus with respect to supplementation of either vitamin,
but several authors suggest that regular checks and, if necessary, supplementation
is necessary, whereby in the case of vitamin A in particular attention must be paid
to its potential teratogenicity, and daily dose of 5000 IU/day (ideally in the form
of β-carotene) should not be exceeded [30], [32]. Furthermore, a dose of 15 mg zinc per day and daily supply of at least 60 g of
protein are recommended [30], [31], [33].
Pre-eclampsia
The growing incidence of pre-eclampsia worldwide is associated, among others, with
the rise in pathological obesity [41], [42], [43]. Whereas approximately 2 – 8% of all pregnant women suffer pre-eclampsia [44], it can affect up to 13% of patients with grade 3 obesity [41]. Numerous studies have confirmed that bariatric surgery prior to conception can
reduce the risk by up to 75% compared with an obese control group [45] in whom surgery was not performed [5], [46], [47], [48], [49], [50]. The effect appears to be more pronounced during the first two years postoperatively
[51].
Foetal development
Several studies suggest that the risk of a foetus being small for gestational age
(SGA) is increased in pregnancy after gastric bypass [14], [51], [52]. This complication could be related to the amount of weight lost by the mother and
the surgical technique, as the risk of SGA appears to be less pronounced after a purely
restrictive intervention [14]. The direct consequence of foetal adaptations in an undernourished mother [53] are metabolic effects reported in SGA children lasting through to adulthood [54]. At present, long-term data on the children of mothers having undergone bariatric
surgery are still sparse; hence, so far only a limited assessment can be made regarding
the extent to which the postoperative intrauterine conditions could influence the
childʼs later development.
The increased risk of premature delivery (spontaneous or medically induced) must be
noted, moreover, especially if the woman becomes pregnant during the first year after
bariatric surgery. This could be attributable to increased weight loss during pregnancy,
which may result in foetal malnutrition and premature delivery [55]. The data in this respect are not conclusive. In several studies, no significant
correlation could be found between the increased risk of premature birth and prior
bariatric surgery [51], [52]. The American College of Obstetricians and Gynecologists (ACOG) [33] and other authors [32] recommend delaying pregnancy until at least 12 – 18 months after bariatric surgery,
but this is not supported by all current studies [56]. Obstetricians must bear in mind that the optimal timing for pregnancy following
gastric bypass has not yet been ascertained.
The literature reports that, compared with normal pregnancies, there is a slight but
not statistically significant increase in the rates of intrauterine foetal death (IUFT)
and perinatal mortality after bariatric surgery [52].
Growth checks at intervals of several weeks and registration with a perinatal centre
are advisable with a view to preventing or minimising long-term consequences.
Surgical complications
The incidence of herniation after gastric bypass can reach 5%. Pregnant women have
an even higher risk after bariatric surgery, possibly due to increased intra-abdominal
pressure exerted by the pregnant uterus on the intestine [57]. In the event of acute abdomen, the obstetrician must also consider internal hernia
and refer the patient with a view to surgery. If internal hernia is suspected, the
patient should fast and be admitted for pain management and monitoring. If the pain
recurs after building up the diet, subacute surgery should be performed. If the pain
symptoms persist despite treatment and fasting, acute surgery will be necessary to
prevent intestinal necrosis and foetal complications [58]. Timely diagnosis and treatment of an intra-abdominal hernia are crucial to maternal
and foetal health, as deaths of both mother and child have been reported in the literature
[59].
Lactation
Malabsorption and subsequent malnutrition are widespread consequences following bariatric
surgery. Current studies are examining whether this nutrient deficiency affects the
composition of breast milk; the data available so far provide no indication that the
composition of the breast milk is inadequate after bariatric surgery [60]. In the light of current data, breastfeeding is certainly to be recommended [32], [60].
Conclusion
Bariatric surgery is associated with maternal and foetal effects on pregnancy [5]. Preconceptional counselling from the obstetrician is urgently recommended to ensure
that the woman is aware of the potential risks of pregnancy following bariatric surgery.
At first presentation during pregnancy, blood should be taken to determine the iron
and vitamin status and intervene, where necessary. The patient should be informed
about the symptoms and the avoidance of a dumping syndrome, and a diurnal blood glucose
profile should be taken between week 24 and 28 of pregnancy [23]. The OGTT is contraindicated in pregnancy after bariatric surgery due to the increased
risk of hypoglycaemia [13]. Regular ultrasound checks are recommended for monitoring foetal growth. Vaginal
delivery and breastfeeding are not contraindicated.
